Phytophthora medicaginis
(Phytophthora root rot of lucerne)

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Identity

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Preferred Scientific Name

• Phytophthora medicaginis E.M. Hansen & D.P. Maxwell, 1991

Preferred Common Name

• Phytophthora root rot of lucerne

Other Scientific Names

• Phytophthora megasperma Drechsler
• Phytophthora megasperma f.sp. medicaginis T.L. Kuan & Erwin
• Phytophthora sojae f.sp. medicaginis Faris

International Common Names

• English: Phytophthora root rot of alfalfa; Phytophthora root rot of chickpea

Local Common Names

• India: foot blight of gram

Summary of Invasiveness

Top of page P. medicaginis is a pathogen that can be either soil or water borne; its invasiveness is limited to periods when the soil is very wet or flooded such as during flood irrigation, heavy rain periods and natural flood events. The success of invasion by P. medicaginis is dependant on the presence of a susceptible host such as lucerne or chickpea. Flooding facilitates the transportation of zoospores and makes the host more receptive to infection (Kuan and Erwin, 1980b). P. medicaginis may also be spread as oospores in contaminated soil and infected plants but the very wet soil conditions are required to stimulate their germination, development of zoospores and infection of the host (Erwin and Ribeiro, 1996). The roots of infected plants develop a dark-brown rot and soon lose their efficiency in nutrient and water transport resulting in additional symptoms of yellowing of leaves, wilting, stunting and finally death. Large areas of plants in low lying locations or poorly drained soil are affected and often die (Lowe et al., 1987; Dale and Irwin, 1990) causing considerable economic loss.

Taxonomic Tree

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• Domain: Eukaryota
•     Kingdom: Chromista
•         Phylum: Oomycota
•             Class: Oomycetes
•                 Order: Peronosporales
•                     Family: Peronosporaceae
•                         Genus: Phytophthora
•                             Species: Phytophthora medicaginis

Notes on Taxonomy and Nomenclature

Top of page Phytophthora medicaginis was formally recognized as a distinct species by Hansen and Maxwell (1991), and is characterized most readily by its aggresive pathogenicity to lucerne and chickpea. In earlier reports it was included in the P. megasperma 'complex', sometimes with P. sojae as P. megasperma var. sojae, and sometimes as P. megasperma f.sp. medicaginis. However, it is morphologically, culturally and behaviourally distinct from the other species of the megasperma complex and molecular data shows it to be only distantly related to them. It is sometimes difficult to interpret the older literature because of varying species concepts. For example, some authors included all Phytophthora isolates recovered from lucerne within P. megasperma f.sp. medicaginis, without regard for oospore size or aggressiveness. Large-spored, mildly pathogenic 'megasperma-type' isolates are P. megasperma not P. medicaginis.

Description

Top of page The morphological descriptions of this and other species of Phytophthora are based on in vitro observations and are often insufficient for identification. P. megasperma var. sojae (Waterhouse, 1963) describes P. medicaginis as well as several other distinct species of the P. megasperma complex (Hansen et al., 1986). Homothallism, relatively small oogonia and ovoid, non-papillate sporangia are key features. The formal species description of Hansen and Maxwell (1991) includes: Homothallic features, with paragynous or amphigynous antheridia and oogonia 37-39 µm diameter, occasionally 32-43 µm. Oospores are 28-34 µm diameter, with oospore walls 2-4 µm thick. Sporangia are ovoid to ellipsoid or pyriform, without papillae, and 50-60 µm long by 24-30 µm wide. Growth is slow at 4-5 mm per day on agar media at 25-26°C and little or no growth occurs at 5°C or 35°C. The colony is dense, without pattern, and with an appressed margin.

Distribution

Top of page P. medicaginis has been introduced to most areas of the world where lucerne is grown. Its distribution is usually restricted to localised areas with poor drainage. These include areas that are topographically flat or have depressions or areas with heavy textured soils with high clay content (Wilkinson and Millar, 1982; Barta and Schmitthenner, 1986; Myatt et al., 1993). In regions where P. medicaginis is present and damaging, it is usually not found in every field (Aguirre et al., 1983; Basu, 1983; Dale and Irwin, 1990; Munkvold and Carlton, 1995). Despite its reported occurrence in most lucerne production areas throughout the world, P. medicaginis has not been reported from Europe. Many reports carry some degree of uncertainty, because of continuing changes in the species concept. CMI (1987), for example, does not distinguish the several species of the 'P. megasperma complex'. The accompanying list of countries is therefore based on an interpretation of the older literature. Where a P. megasperma-type fungus is associated with a serious root rot of lucerne, it is a fair assumption that P. medicaginis is involved. Reports of P. medicaginis in lucerne or chickpea since its formal description (Hansen and Maxwell, 1991) are generally reliable. The pathogen may well be present but unreported in other countries with a history of lucerne cultivation.

The situation in Europe deserves special attention. If in fact the fungus is absent or uncommon in large parts of Europe, then special efforts should be made to prevent its introduction. It is important to note that the fungus identified as P. megasperma from chickpea in Spain (Trapero-Casas et al., 1992) is in fact a distinct taxon (Liew and Irwin, 1994; Irwin et al., 1996).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

Top of page The centre of origin of P. medicaginis is unknown. However, because this pathogen has a narrow host range of chickpea and lucerne, it has been suggested that it has co-evolved with these hosts in Transcaucasia (Irwin et al., 1995). Single introductions from this centre may have resulted in the Australian and USA populations of P. medicaginis. These introductions were most likely of an accidental nature involving the transport of contaminated soil or infected plant material.

Risk of Introduction

Top of page The spread of P. medicaginis is by survival structures (oospores and chlamydospores) in infected plant tissue and in soil and by zoospores in water. Oospores and chlamydospores may be spread short distances within fields during tillage, or further to different fields in soil adhering to vehicles, tillage implements or animals' feet. Zoospores in their encysted state may spread even greater distances during flood events (Erwin and Ribeiro, 1996). In regions where P. medicaginis is already present and damaging, it is usually not found in every field (Aguirre et al., 1983; Basu, 1983; Dale and Irwin, 1990; Munkvold and Carlton, 1995).

Soil contaminated with oospores of P. medicaginis adhering to tillage implements or to the footwear of travellers or the feet of live export animals are the most likely means of accidental introduction of this pathogen. These carriers may travel vast distances with modern transport, particularly air transport, and oospores can survive for 3.5 years in the soil (Pratt and Mitchell, 1975; Stack and Millar, 1985b).

Floodwaters carrying zoospores also are a likely means of accidental introduction to new areas (Erwin and Ribeiro, 1996). However, the spread by this means is restricted to areas below the source of infection in the local geomorphic drainage system.

Alfalfa seedlings (sprouts) infected with P. medicaginis also may pose a potential threat in the introduction of this pathogen to new regions. Alfalfa sprouts used in the food industry may be transported great distances by air, rail or road transport and P. medicaginis infecting such plants would readily survive these journeys. Although it may be very unlikely for alfalfa sprouts to be infected with P. medicaginis because this pathogen is not seedborne and water used for their germination should not be contaminated, the possibility remains. Alfalfa or lucerne seedlings are very susceptible to infection by P. medicaginis and are used to bait the fungus in the isolation of this pathogen (Erwin and Ribeiro, 1996).

It is unlikely that P. medicaginis would be deliberately introduced into a region because it has a narrow host range of mainly agricultural plants and would not be a suitable candidate for the biological control of weeds, other pathogens or animal pests.

P. medicaginis is not known from Europe, and is potentially damaging to lucerne and chickpea if introduced there. In both international and local situations, sanitary precautions, aimed at limiting transport of infected plants and infested soil, will greatly reduce the risk of introduction or local spread.

Hosts/Species Affected

Top of page P. medicaginis has a narrow host range in nature and is primarily a pathogen of the family Fabaceae. It is only known as an agricultural pathogen. Lucerne (Medicago sativa) is the primary host (Erwin and Ribeiro, 1996). Other species of Medicago, notably the annual species, are also susceptible under field test conditions (Haan et al., 1996). Chickpea (Cicer arietinum) is susceptible and damaged in the field in USA, Australia (Irwin and Dales, 1982) and India (Suryanarayana and Pathak, 1968). In Spain, root rot of Cicer is caused by other Phytophthora species distinctly different from P. medicaginis in genetic, morphological and cultural parameters (Liew and Irwin, 1994); P. medicaginis has not been reported (Erwin and Ribeiro, 1996). Sainfoin (Onobrychis viciifolia) is susceptible in the seedling stage (Gray and Wofford, 1987). Hedysarum spp. have been shown to be susceptible in glasshouse tests with H. carnosum being as equally susceptible as chickpea (Southwell and Crocker, 2005).

P. medicaginis infects and causes significant disease in a variety of unrelated hosts under conditions of artificial inoculation, especially when soil flooding is prolonged or repeated (Hamm and Hansen, 1981; Wilcox and Mircetich, 1987). However, it has never been isolated from these other plant species in the field, and host preference remains an important diagnostic characteristic of this pathogen.

Growth Stages

Top of page Pre-emergence, Seedling stage, Vegetative growing stage

Symptoms

Top of page Germinating seed and seedlings of lucerne are infected and killed rapidly, with the disease appearing as damping off. Older plants are also infected, with characteristic reddish-brown or black root lesions developing into root rot disabling some or all of the root system. Mature plants may be killed, especially following repeated infection in poorly drained areas, but more often exhibit chlorosis and reduced growth (Erwin, 1954; Schmitthenner, 1964). Infected plants are prone to winter injury, including frost heaving.

In chickpea, Phytophthora root rot is characterized by chlorosis and desiccation of foliage, decay of lateral roots, small brown lesions that develop into extensive dark-brown lesions on the taproot, and the development of girdling lesions with reddish-brown margins extending to the collar (Vock et al., 1980).

List of Symptoms/Signs

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Biology and Ecology

Top of page Genetics

P. medicaginis has a chromosome number of 12-15 (Hansen and Maxwell, 1991). Molecular markers have been used to assess the genetic diversity of P. medicaginis populations using isolates collected from Australia and the USA and these were found to be very uniform (Liew and Erwin, 1994; Irwin et al., 1995). P. medicaginis does not hybridize with other Phytophthora spp. such as P. sojae (Layton and Kuhn, 1988; Nygaard et al.,1989) or P. megasperma (Hansen, 1987).

Physiology and Phenology

The long-term survival strategy of P. medicaginis is through the production of thick-walled oospores. These may survive for up to 3.5 years in the soil (Pratt and Mitchell, 1975; Stack and Millar, 1985b). The fungus may also survive as chlamydospores in infected plant tissue (Basu, 1980).

Reproductive Biology

The life cycle of P. medicaginis is similar to that of other homothallic species of Phytophthora (Erwin, 1965). The mycelium is self-fertile and oospores are formed, in culture and in infected roots in soil, following the fusion of oogonia and antheridia. Oospores are thick-walled spores that can survive adverse conditions for long periods. Typically, they germinate to produce a sporangiophore and sporangia in water-saturated soil (Salvatore et al., 1973). Germination of oospores is stimulated by exudates from host roots and occurs at pH 3.5-10.5 with an optimum of pH 6 (El-Hamalawi and Erwin, 1986). Zoospores are released into the soil solution and follow chemotactic gradients to host roots, where they encyst and then germinate, forming vegetative hyphae. Hyphae penetrate and colonize host roots, killing host tissue as they advance. Chlamydospores may be formed on the vegetative hyphae. They are typically thin-walled, in contrast to oospores, but also serve as survival structures (Basu, 1980). Oogonia and antheridia form on the hyphae in roots and fuse, especially as soil dries or host tissue dies.

Primary inoculum is usually oospores or chlamydospores in infected root fragments in the soil. Germination and release of zoospores can occur in water saturated soil at temperatures from 5 to 30°C but growth is best at about 25°C (Erwin and Ribeiro, 1996). Zoospores swim for only a few millimetres through the soil matrix, but can be carried for much longer distances in flowing water such as in flood irrigation and during periods of natural flooding following heavy rain events. They remain motile for several hours and may encyst on any surface, especially if agitated. However, they concentrate on host roots, frequently where lateral roots emerge from the taproot (Marks and Mitchell, 1971; Chi and Sabo, 1978), on nodules of Rhizobium (Gray and Hine, 1976) and on stomata near the soil line on stems of chickpea (Dale and Irwin, 1991b).

Environmental Requirements

P. medicaginis occurs in temperate to sub-tropical environments where lucerne or chickpea are grown. Low lying and poorly drained areas and soils of heavy texture high in clay content are common habitats of P. medicaginis because they are prone to water saturation following heavy rain, flooding or flood irrigation (Lehman et al., 1968; Pulli and Tesar, 1975; Wilkinson and Millar, 1982; Alva et al., 1985, 1986; Barta and Schmitthenner, 1986; Myatt et al., 1993).

Flooding from either irrigation or natural rainfall events may act as a trigger event causing P. medicaginis to become invasive because its zoospores can be transported readily from one site to another (Erwin and Ribeiro, 1996) and flooding increases the attractiveness and susceptibility of lucerne seedlings to this pathogen (Kuan and Erwin, 1980b).

Associations

Aphanomyces euteiches can be associated with P. medicaginis in lucerne fields, with both pathogens causing damage to the roots of these plants. In a study of lucerne fields in 45 of 99 counties in Iowa, USA, Munkvold and Carlton (1995) detected P. medicaginis and A. euteiches in soil and root samples in 26 and 31 counties, respectively. Of the soil samples infested with P. medicaginis, 81% were also infested with A. euteiches. In some cases where A. euteiches is also present in lucerne fields in North America it may be the more serious pathogen (Abbo and Irwin, 1990; Holub and Grau, 1990a).

Notes on Natural Enemies

Top of page Little is known about natural enemies of P. medicaginis, although many elements of the soil microflora and fauna undoubtedly limit the fungus under some conditions (Sneh et al., 1977). Under experimental conditions, antagonistic bacteria inhibit the fungus and reduce disease (Handelsman et al., 1990; Myatt et al., 1993). A number of Streptomyces isolates were found by Xiao et al. (2002) to reduce disease in lucerne caused by P. medicaginis both in vitro and in naturally infested field soil.

Means of Movement and Dispersal

Top of page Natural dispersal

The natural dispersal of P. medicaginis is by zoospores in wet soil conditions. Zoospores swim for only a few millimetres through the soil matrix, but can be carried for much longer distances in flowing water such as in flood irrigation and during periods of natural flooding following heavy rain events (Erwin and Ribeiro, 1996).

Agricultural practices

Soil contaminated with oospores of P. medicaginis may be relocated a metre or more to nearby uncontaminated areas by soil tillage practices. Contaminated soil adhering to tillage implements or the hooves of livestock may be transported much greater distances.

Seedborne Aspects

Top of page There is no evidence that P. medicaginis is seedborne.

Plant Trade

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Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Leaves
Stems (above ground)/Shoots/Trunks/Branches
True seeds (inc. grain)
Wood

Wood Packaging

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Impact Summary

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Impact

Top of page There is apparently no specific information available on the economic impact of P. medicaginis on a regional scale. It is widespread in many lucerne production areas and reduces stand density, winter hardiness (Tu, 1980; Basu and Butler, 1991; Wiersma et al., 1997) and forage yield of individual plants and entire fields (Lowe et al., 1987). A 75% stand reduction in the first year after sowing a susceptible cultivar in naturally infected fields (Gray et al., 1983) is perhaps representative of severe damage. In a different study, individual infected and healthy plants were monitored for 2 years; forage yield of root-rotted plants was reduced by 68% (Gray et al., 1988). In Wisconsin, USA, lucerne cultivars with good field resistance to Phytophthora root rot yielded 40% more than susceptible cultivars and combined resistance to Phytophthora and Aphanomyces increased yield still more (Wiersma et al., 1995). Estimating damage from comparisons of susceptible and resistant cultivars probably underestimates total loss, because even 'resistant' cultivars may be infected and damaged, especially under very wet conditions (Erwin and Ribeiro, 1996).

In eastern Australia, Phytophthora root rot caused by P. medicaginis is regarded as one of the major constraints to lucerne production on poorly drained soil types (Irwin, 1974; Rogers et al., 1978).

P. medicaginis is a major disease of chickpea in Australia (Vock et al., 1980; Irwin and Dales, 1982; Brinsmead et al., 1985; Knights et al., 2003). Large areas of chickpea in a field can be killed causing growers to abandon part or all of affected crops (Dale and Irwin, 1990b). Yield losses can exceed 50% for individual crops and reach 20% on a regional basis in years with above average rainfall (Knights et al., 2003).

Environmental Impact

Top of page The impact of P. medicaginis on the natural environment has not been reported. However, it is likely to be minimal because of its narrow host range of agricultural plants within the Fabaceae. Lucerne and chickpea are the primary hosts (Erwin and Ribeiro, 1996; Irwin and Dales, 1982). Annual species of Medicago are also susceptible under field test conditions (Haan et al., 1996). Annual medics and many other legumes are common in the natural environment. However, the effect of P. medicaginis on many of these legumes and the interaction of these effects with other plants are unknown.

Impact: Biodiversity

Top of page There are no reported impacts of P. medicaginis on biodiversity. P. medicaginis does not hybridize with other Phytophthora spp. such as P. sojae (Layton and Kuhn, 1988; Nygaard et al.,1989) and P. megasperma (Hansen, 1987).

Social Impact

Top of page There are no documented studies of the social impact of P. medicaginis on human activities which would indicate a low impact. However, root rot of lucerne and chickpea caused by this pathogen can result in high economic losses on individual farms and, logically, this reduces the livelihood of these primary producers.

Diagnosis

Top of page Isolation of P. medicaginis is best accomplished from active lesions on the roots of symptomatic but not dead plants, and by baiting from the soil. Roots should be carefully washed and pieces 2-4 mm long cut from the margins of lesions. Pieces of larger roots can be surface sterilized and then placed on selective agar medium containing pimaricin and antibacterial antibiotics (Erwin and Ribeiro, 1996). In some isolation procedures washing the roots for 2 h under running tap water has been used instead of surface sterilizing between the initial washing and plating onto the selective medium (Southwell and Crocker, 2005). Baiting is accomplished by floating newly germinated lucerne seedlings on flooded soil samples, then transferring them to selective media as discoloration develops (Erwin and Ribeiro, 1996).

Distinguishing P. medicaginis from other species of Phytophthora on morphological features alone is difficult, even for those familiar with the genus. The pattern of growth on agar media is distinctive for those familiar with this fungus. All the characteristics of the sporangia, oogonia, antheridia and oospores as originally described (Hansen and Maxwell, 1991) need to be considered to distinguish this fungus. Strong pathogenicity to lucerne and chickpea is an important species character. In critical cases, identification should be confirmed with molecular techniques. Vandemark and Barker (2003) have developed a real-time fluorescent PCR method that can not only detect P. medicaginis in lucerne but quantify it. This will be particularly useful in breeding programmes aiming to improve plant resistance to this pathogen.

Detection and Inspection

Top of page Phytophthora root rot is indicated by the pattern of disease in low-lying areas of affected fields and the characteristic dark lesions on tap roots of symptomatic plants. Commercially available ELISA test kits can be used to confirm the presence of Phytophthora, but not the species involved. Liew et al. (1998) have developed a PCR-based technique for the specific detection of P. medicaginis and used it successfully in detecting P. medicaginis in lucerne stems infected under greenhouse conditions and field-infected lucerne roots.

Similarities to Other Species/Conditions

Top of page Other Oomycetes can cause similar symptoms on lucerne and chickpea seedlings in the field, but severe damage to mature plants is usually caused by P. medicaginis. Aphanomyces euteiches is often present with P. medicaginis and may be damaging in seedling stands of lucerne in parts of North America. In some cases it may be the more serious pathogen (Abbo and Irwin, 1990; Holub and Grau, 1990a). It causes damping off and decay of the fine roots, but is usually not associated with lesions on tap roots. Seedlings attacked by Aphanomyces often remain upright, in contrast to the collapse of seedlings infected by Pythium or P. medicaginis (Stuteville and Erwin, 1990). Pythium species are generally confined to the fine roots, killing young seedlings, but causing little or no damage on mature plants.

Other species of Phytophthora may be present on lucerne or chickpea, but most lack the host specificity of P. medicaginis (Schmitthenner, 1964) and are not associated with severe disease. Isolation and identification of the pathogen is necessary to confirm. The situation is confused by recent changes in species concept and nomenclature (Hansen and Maxwell, 1991). P. megasperma, with larger oospores and a broad host range, is reported from alfalfa growing in Ontario, Canada (Barr, 1980; Faris et al., 1983; 1986; 1989), and Oregon, USA (Hansen and Hamm, 1983; Hansen and Maxwell, 1991). Species of Phytophthora from lucerne in California, USA, that grow at temperatures greater than 30°C are not P. medicaginis (Ribeiro et al., 1978; Forster and Coffey, 1993). In Spain, a fungus damaging chickpea has been confused with P. megasperma, but is in fact a new species, not P. medicaginis. (Liew and Irwin, 1994). Phytophthora megasperma isolates with small oospores like P. medicaginis, but lacking host specificity, have been recovered from lucerne field soils in Japan (Matsumoto and Sato, 1985; Hansen et al., 1986).

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Control of Phytophthora root rot of lucerne is possible in most situations by combinations of improved water management, use of resistant cultivars and crop rotation. Assuring good drainage is the first step in almost all situations. This can be accomplished by selecting well-drained soils for establishment of lucerne crops or grading fields to eliminate low spots (Erwin and Ribeiro, 1996), by installing drainage tile or ditches to remove water, by subsoiling to break up impervious soil layers, and by avoiding excessive irrigation (Lehman et al., 1968).

Phytophthora root rot in chickpea in Australia has been partially controlled by using moderately resistant varieties, by seed applications of fungicides such as metalaxyl, by alternative crop rotations and by reduced irrigation regimes (Myatt et al., 1993).

Lucerne and chickpea cultivars vary widely in their tolerance of Phytophthora root rot, and selections with useful field resistance are available in most regions where root rot is a problem (Lehman et al., 1967; Irwin, 1974; Irwin and Maxwell, 1980; Frosheiser, 1980; Brinsmead et al., 1985; Lowe et al., 1987; Dale and Irwin, 1991a; Ansar et al., 1995). However, resistance is relative and losses may still be heavy in seedling stands and in chronically poorly drained soils (Erwin and Ribeiro, 1996). If Aphanomyces euteiches is also present, then it may be necessary to use cultivars with dual tolerance (Holub and Grau, 1990b). In the future, new resistant cultivars produced by genetic engineering may be available (Masoud et al., 1996). A genetic linkage map has been developed for lucerne grown in northern Australia (Musial et al., 2005). Quantitative trait loci (QTLs) involved in resistance to P. medicaginis were identified in a backcross population. This genetic linkage map provides an entry point for future molecular-based improvement of disease resistance in lucerne in Australia.

There has been a recent advance in chickpea breeding for resistance to Phytophthora root rot with the evaluation of wild Cicer species for resistance to P. medicaginis. Cicer echinospermum accessions have shown significantly greater resistance to P. medicaginis than chickpea genotypes, both in the glasshouse and in the field (Knights et al., 2003). C. echinospermum accessions can be readily crossed with chickpea to give fertile progeny and so provide a readily available source of resistance for this pathogen. However, while this source of resistance provides extended scope in breeding programmes, it is incomplete and chickpea with this resistance remain partially susceptible under extreme disease pressure. Thus, other disease control methods in conjunction with plant resistance should not be overlooked.

Crop rotations of 3 years or longer are necessary to reduce P. medicaginis populations in fields because of the long-lived oospores (Pratt and Mitchell, 1975; Stack and Millar, 1985b). Populations may quickly recover to damaging levels after a rotation unless drainage is improved and resistant cultivars are employed. Chemical control of Phytophthora root rot is possible, but is seldom economically feasible. The Oomycete-active fungicides will limit development of root rot in seedlings and in established plants, but will not eradicate the pathogen from infested soil. It may be feasible to provide critical short-term protection to seedling stands by fungicidal seed treatments before sowing (Rhodes and Myers, 1989). The usefulness of metalaxyl to control P. medicaginis may soon be reduced with the discovery of an isolate of the fungus insensitive to this fungicide (Stack and Millar, 1985a). Protection of seedlings can be obtained under experimental conditions by seed treatment with biological agents such as the bacterium Bacillus cereus (Silo-Suh et al., 1994). Myatt et al. (1993) found that Pseudomonas cepacia (7 strains) and Pseudomonas fluorescens (2 strains) were able to limit or delay chickpea seedling disease caused by P. medicaginis in a pasteurized soil. However, commercial application of this type of control has yet to be demonstrated.

An integrated disease management programme incorporating host resistance and including cultural, chemical or biological methods needs to be implemented to best control P. medicaginis.

References

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Abbo EO; Irwin JAG, 1990. Aphanomyces euteiches, a possible cause of poor lucerne establishment in the Lockyer Valley, Queensland. Australian Journal of Experimental Agriculture, 30(3):361-364

Ablett GR; Beversdorf WD, 1990. RCAT Alliance soybean. Canadian Journal of Plant Science, 70(3):855-856.

Ablett GR; Tanner JW, 1993. RCAT Tabby soybean. Canadian Journal of Plant Science, 73(4):1103-1104.

Aguirre RJ; Hine RB; Schonhorst MH, 1983. Distribution of Phytophthora root rot of alfalfa in Central Mexico and development of disease resistance in Mexican cultivars of alfalfa. Plant Disease, 67(1):91-94

Albersheim P; Valent BS, 1978. Host-pathogen interactions in plants. Plants, when exposed to oligosaccharides of fungal origin, defend themselves by accumulating antibiotics. Journal of Cell Biology, 78(3):627-643.

Allen EH; Thomas CA, 1972. Antifungal polyacetylene compounds associated with Phytophthora resistance in safflower. Phytopathology, 62(6):667.

Alva AK; Lanyon LE; Leath KT, 1985. Excess soil water and Phytophthora root rot stresses of Phytophthora root rot sensitive and resistant alfalfa cultivars. Agronomy Journal, 77(3):437-442

Alva AK; Lanyon LE; Leath KT, 1986. Production of alfalfa in Pennsylvania soils of differing wetness. Agronomy Journal, 78(3):469-473.

Anderson TR, 1987. Fungi isolated from stems and roots of soybean in Ontario. Canadian Plant Disease Survey, 67(1):3-5; 16 ref.

Anderson TR; Buzzell RI, 1982. Efficacy of metalaxyl in controlling Phytophthora root and stalk rot of soybean cultivars differing in field tolerance. Plant Disease, 66(12):1144-1145

Anderson TR; Buzzell RI, 1992. Diversity and frequency of races of Phytophthora megasperma f.sp. glycinea in soybean fields in Essex County, Ontario, 1980-1989. Plant Disease, 76(6):587-589

Anderson TR; Buzzell RI, 1992. Inheritance and linkage of the Rps7 gene for resistance to Phytophthora rot of soybean. Plant Disease, 76(9):958-959

Anderson TR; Montpetit JM, 1994. Phytophthora rot of soybean caused by Phytophthora sojae found in Quebec, Canada. Plant Disease, 78(12):1218

Ansar M; Bajwa R; Aslam SS; Akhtar AS, 1995. Selection for resistance against root/collar rot of chickpea using culture filtrate of Phytophthora megasperma var. sojae Drechsler. Pakistan Journal of Phytopathology, 7(2):196-198; 7 ref.

Aslam M; Majid K; Shahid M; Saleem A, 1994. Root rot of cabbage caused by Phytophthora megasperma f.sp. sojae Drechsler - a new record from Pakistan. Pakistan Journal of Phytopathology, 6(2):155-156

Athow KL, 1985. Phytophthora root rot of soybean. In: Shibles R, ed. Proceedings, World Soybean Research Conference III. Boulder, USA: Westview Press, 575-581.

Athow KL; Laviolette FA; Abney TS, 1974. Reaction of soybean germplasm strains to four physiologic races of Phytophthora megasperma var. sojae. Plant Disease Reporter, 58(9):789-792.

Barr DJS, 1980. Heterothallic-like reaction in the large-oospore form of Phytophthora megasperma. Canadian Journal of Plant Pathology, 2(3):116-118

Barreto D; Gurfinkel BS de; Fortugno C, 1995. Races of Phytophthora sojae in Argentina and reaction of soybean cultivars. Plant Disease, 79(6):599-600

Barta AL; Schmitthenner AF, 1986. Interaction between flooding stress and Phytophthora root rot among alfalfa cultivars. Plant Disease, 70(4):310-313

Basu PK, 1980. Production of chlamydospores of Phytophthora megasperma and their possible role in primary infection and survial in soil. Canadian Journal of Plant Pathology, 2(2):70-75

Basu PK, 1983. Survey of eastern Ontario alfalfa fields to determine common fungal diseases and predominant soil-borne species of Pythium and Fusarium.. Canadian Plant Disease Survey, 63(2):51-54; [1 fig., 2 tab.]; 19 ref.

Basu PK; Butler G, 1991. A field study of Phytophthora root rot and cold stress on Vernal and Apollo alfalfa. Forage Notes, 35:4-12

Baudry A; Morzieres JP; Ellis R, 1991. Effect of Phytophthora spp. on kiwifruit in France. New Zealand Journal of Crop and Horticultural Science, 19(4):395-398

Baudry A; Morzieres JP; Poillon P, 1993. Actinidia deliciosa, diebacks, root rots and Phytophthora. Phytoma, 446:44-47

Bernardi AL; Rose IA; Andrews JA, 1995. Glycine max (L.) Merr. (soybean) cv. Banjalong. Australian Journal of Experimental Agriculture, 35(1):118; 3 ref.

Beversdorf WD; Tanner JW; Gostovic P; Montminy W; Hume DJ, 1994. OAC Talbot soybean. Canadian Journal of Plant Science, 74(1):137-138.

Bhat RG; Olah AF; Schmitthenner AF, 1992. Characterization of universally avirulent strains of Phytophthora sojae. Canadian Journal of Botany, 70(6):1175-1185

Bhattacharyya MK; Ward EWB, 1987. Temperature-induced susceptibility of soybeans to Phytophthora megasperma f.sp. glycinea: phenylalanine ammonia-lyase and glyceollin in the host; growth and glyceollin I sensitivity of the pathogen. Physiological and Molecular Plant Pathology, 31(3):407-419

Boerma HR; Harris HB; Wood ED, 1980. Registration of Wright soybean (Reg. No. 130). Crop Science, 20(2):287

Borner H; Schatz G; Grisebach H, 1983. Influence of the systemic fungicide metalaxyl on glyceollin accumulation in soybean infected with Phytophthora megasperma f.sp. glycinea. Physiological Plant Pathology, 23(1):145-152

Brinsmead RB; Rettke ML; Irwin JAG; Langdon PW, 1985. Resistance in chickpea to Phytophthora megasperma f.sp. medicaginis. Plant Disease, 69(6):504-506

Bush EA; Stromberg EL; Hong CX; Richardson PA; Kong P, 2006. Illustration of key morphological characteristics of Phytophthora species identified in Virginia nursery irrigation water. Plant Health Progress, June:1-10. http://www.plantmanagementnetwork.org/php/

Buzzell RI; Anderson TR, 1992. Inheritance and race reaction of a new soybean Rps1 allele. Plant Disease, 76(6):600-601

Buzzell RI; Anderson TR; Rennie BD, 1987. Harosoy Rps isolines. Soybean Genetics Newsletter, 14:79-81

Cacciola SO; Scarito G; Salamone A; Fodale AS; Mulé R; Pirajno G; Sammarco G, 2007. Phytophthora species associated with root rot of olive in Sicily. Bulletin OILB/SROP [IOBC/WPRS, Working group "Integrated Protection of Olive Crops" Proceedings of the meeting, Florence, Italy, 26-28 October 2005.], 30(9):251. http://www.iobc-wprs.org

Campos VP; Schmitt DP, 1981. Histological analysis of the Phytophthora root and stem rot disease of soybean. Fitopatologia Brasileira, 6(2):229-236

Canaday CH; Schmitthenner AF, 1982. Isolating Phytophthora megasperma f.sp. glycinea from soil with a baiting method that minimizes Pythium contamination. Soil Biology & Biochemistry, 14(1):67-68

Carruthers FL; Shum-Thomas T; Conner AJ; Mahanty HK, 1995. The significance of antibiotic production by Pseudomonas aureofaciens PA147-2 for biological control of Phytophthora megasperma root rot of asparagus. Plant and Soil, 170(2):339-344

Caviness CE; Riggs RD; Rupe JC, 1991. Registration of 'Walters' soybean. Crop Science, 31(3):850; 5 ref.

Cheah LH, 1987. Metalaxyl controls Phytophthora rot of asparagus. Proceedings of the New Zealand Weed and Pest Control Conference, No. 40:64-66

Chen PS, 1994. The relation between Phytophthora megasperma var. sojae and Meloidogyne spp. and their control. Technology and Extension of Plant Protection, No. 2, 38-39.

Chevis HW; Stukely MJC, 1982. Mortalities of young established radiata pine associated with Phytophthora spp. in the Donnybrook Sunkland plantations in Western Australia. Australian Forestry, 45(3):193-200

Chi CC; Sabo FE, 1978. Chemotaxis of zoospores of Phytophthora megasperma to primary roots of alfalfa seedlings. Canadian Journal of Botany, 56(7):795-800

Cianzio SR; Tachibana H; Mansur LM; Fehr WR; Niblack TL; Schultz SP; Ruff R; Bidne K, 1991. Registration of A20 soybean germplasm resistant to brown stem rot, soybean cyst nematode, and iron deficiency chlorosis. Crop Science, 31(6):1713-1714; 3 ref.

CMI, 1987. Distribution Maps of Plant Diseases, No. 157, edition 4. Wallingford, UK: CAB International.

Cohen SD, 1984. Detection of mycelium and oospores of Phytophthora megasperma forma specialis glycinea by vital stains in soil. Mycologia, 76(1):34-39

Craigmiles JP; Hartwig EE; Sij JW, 1978. Registration of Dowling soybeans. Crop Science, 18(6):1094.

Cvjetkovic B, 2008. Less frequent diseases of oilseed rape. (RjeÐe ucestale bolesti uljane repice.) Glasilo Biljne Za?tite, 8(5):318-320.

Dale ML; Irwin JAG, 1990. Estimation of inoculum potentials of Phytophthora megasperma f.sp. medicaginis in chickpea fields and the development of a glasshouse resistance assay. Australian Journal of Experimental Agriculture, 30(1):109-114

Dale ML; Irwin JAG, 1991. Glasshouse and field screening of chickpea cultivars for resistance to Phytophthora megasperma f.sp. medicaginis. Australian Journal of Experimental Agriculture, 31(5):663-667

Dale ML; Irwin JAG, 1991. Stomata as an infection court for Phytophthora megasperma f.sp. medicaginis in chickpea and a histological study of infection. Phytopathology, 81(4):375-379

Damirgi SM; Bolton JL; Webster GR; Cook FD, 1979. Resistance and susceptibility of selected alfalfa lines to inoculation with a Phytophthora megasperma isolate. Canadian Journal of Plant Science, 59(4):1153-1154

Diatloff A; Irwin JAG; Rose JL, 1983. Effects of systemic fungicidal seed dressings on the incidence of Phytophthora megasperma, nodulation, and nitrogen fixation in two soybean cultivars. Australian Journal of Experimental Agriculture and Animal Husbandry, 23(120):87-90

Dirks VA; Anderson TR; Bolton EF, 1980. Effect of fertilizer and drain location on incidence of phytophthora rot in soybeans. Canadian Journal of Plant Pathology, 2(3):179-183

Ditterline RL; Dunn RL; Cash SD; Wichman DM; Welty LE; Bergman JL; Eckhoff JLA; Majerus ME; Scheetz JG; Holzworth LK; Blunt KR; Strang LS; Vavrovsky J, 2001. Registration of 'Shaw' alfalfa. Crop Science, 41(1):264-265; 3 ref.

Duncan DR; Paxton JD, 1981. Trifluralin enhancement of Phytophthora root rot of soybean. Plant Disease, 65(5):435-436

Ebel J; Grisebach H, 1988. Defense strategies of soybean against the fungus Phytophthora megasperma f.sp. glycinea: a molecular analysis. Trends in Biochemical Sciences, 13(1):23-27

Elgin JH Jr., Evans DW, Kraft JM, 1972. Occurrence of Phytophthora root rot of alfalfa in Washington. Plant Disease Reporter, 56(10):830-831.

El-Hamalawi ZA; Erwin DC, 1986. Components in alfalfa root extract and root exudate that increase oospore germination of Phytophthora megasperma f.sp. medicaginis. Phytopathology, 76(5):508-513

Erwin DC, 1954. Root rot of alfalfa caused by Phytophthora cryptogea. Phytopathology, 44:700-704.

Erwin DC, 1965. Reclassification of the causal agent of root rot of alfalfa from Phytophthora cryptogea to P. megasperma. Phytopathology, 55:1139-1143.

Erwin DC; Ribeiro OK, 1996. Phytophthora Diseases Worldwide. St Paul, Minnesota, USA: American Phytopathological Society Press.

F÷rster H; Tyler BM; Coffey MD, 1994. Phytophthora sojae races have arisen by clonal evolution and by rare outcrosses. Molecular Plant-Microbe Interactions, 7(6):780-791

Falloon PG, 1986. Phytophthora rot of asparagus. (1) Its effect on production. New Zealand Commercial Grower, 41(8):34-35

Falloon PG; Grogan RG, 1988. Isolation, distribution, pathogenicity and identification of Phytophthora spp. on asparagus in California. Plant Disease, 72(6):495-497

Falloon PG; Mullen RJ; Benson BL; Grogan RG, 1985. Control of Phytophthora rot with metalaxyl in established asparagus. Plant Disease, 69(11):921-923

Faris MA; Sabo FE; Barr DJS, 1983. Studies on Phytophthora megasperma isolates with different levels of pathogenicity on alfalfa cultivars. Canadian Journal of Plant Pathology, 5(1):29-33

Faris MA; Sabo FE; Barr DJS; Lin CS, 1989. The systematics of Phytophthora sojae and P. megasperma. Canadian Journal of Botany, 67(5):1442-1447

Faris MA; Sabo FE; Cloutier Y, 1986. Intraspecific variation in gel electrophoresis patterns of soluble mycelial proteins of Phytophthora megasperma isolated from alfalfa. Canadian Journal of Botany, 64(2):262-265

Ferguson M, 1985. New disease: root rot in soybeans. South Dakota Farm and Home Research, 36(1):17-18

Filonow AB; Lockwood JL, 1985. Evaluation of several actinomycetes and the fungus Hyphochytrium catenoides as biocontrol agents for Phytophthora root rot of soybean. Plant Disease, 69(12):1033-1036

Forster H; Coffey MD, 1993. Molecular taxonomy of Phytophthora megasperma based on mitochondrial and nuclear DNA polymorphisms. Mycological Research, 97(9):1101-1112

Frosheiser FI, 1967. Phytophthora root rot of alfalfa in Minnesota. Plant Disease Reporter, 51:679-681.

Frosheiser FI, 1969. Phytophthora root rot of alfalfa in the upper Midwest. Plant Disease Reporter, 53(8):595-597.

Frosheiser FI, 1980. Conquering Phytophthora root rot with resistant alfalfa cultivars. Plant Disease, 64(10):909-912

Graef GL; Specht JE; Korte LL; White DM, 1993. Registration of 'Lancaster' soybean. Crop Science, 33(2):357; 4 ref.

Graham TL; Kim JE; Graham MY, 1990. Role of constitutive isoflavone conjugates in the accumulation of glyceollin in soybean infected with Phytophthora megasperma. Molecular Plant-Microbe Interactions, 3(3):157-166

Grand LF, 1985. North Carolina Plant Disease Index. North Carolina Agricultural Research Service Technical Bulletin, 240:1-157.

Grau CR, 1985. Assessment and control of Phytophthora root and stem rot of soybean. In: Proceedings, Annual Soybean Research Conference 15. Washington DC, USA: American Seed Trade Association, 54-65.

Gray FA; Bohl WH; Abernethy RH, 1983. Phytophthora root rot of alfalfa in Wyoming. Plant Disease, 67(3):291-294

Gray FA; Bohl WH; Wofford DS, 1988. Relationships of increasing levels of resistance of Phytophthora root rot in alfalfa to stand longevity and yield. Plant Disease, 72(12):1064-1067

Gray FA; Hine RB, 1976. Development of Phytophthora root rot of alfalfa in the field and the association of Rhizobium nodules with early root infections. Phytopathology, 66(12):1413-1417

Gray FA; Wofford DS, 1987. Phytophthora seed rot and seedling blight of sainfoin (Onobrychis viciifolia). Plant Disease, 71(1):74-78

Gray LE; Pope RA, 1986. Influence of soil compaction on soybean stand yield, and Phytophthora root rot incidence. Agronomy Journal, 78(1):189-191

Gupta JP; Erwin DC; Eckert JW; Zaki AI, 1985. Translocation of metalaxyl in soybean plants and control of stem rot caused by Phytophthora megasperma f.sp. glycinea. Phytopathology, 75(7):865-869

Guy SO; Grau CR; Oplinger ES, 1989. Effect of temperature and soybean cultivar on metalaxyl efficacy against Phytophthora megasperma f.sp. glycinea. Plant Disease, 73(3):236-239

Guy SO; Oplinger ES; Grau CR, 1989. Soybean cultivar response to metalaxyl applied in furrow and as a seed treatment. Agronomy Journal, 81(3):529-532

Haan RLde; Sheaffer CC; Samac DA, 1996. First report of Phytophthora medicaginis causing Phytophthora root rot on annual Medicago spp. Plant Disease, 80(6):710; 1 ref.

Hahn MG; Bonhoff A; Grisebach H, 1984. Quantitative localization of the phytoalexin glyceollin I in relation to fungal hyphae in soybean roots infected with Phytophthora megasperma f.sp. glycinea. Plant Physiology, 77(3):591-601

Hamm PB; Hansen EM, 1981. Host specificity of Phytophthora megasperma from Douglas fir, soybean, and alfalfa. Phytopathology, 71(1):65-68

Handelsman J; Raffel S; Mester EH; Wunderlich L; Grau CR, 1990. Biological control of damping-off of alfalfa seedlings with Bacillus cereus UW85. Applied and Environmental Microbiology, 56(3):713-718; 26 ref.

Hansen EM; Brasier CM; Shaw DS; Hamm PB, 1986. The taxonomic structure of Phytophthora megasperma: evidence for emerging biological species groups. Transactions of the British Mycological Society, 87(4):557-573

Hansen EM; Hamm PB, 1983. Morphological differentiation of host-specialized groups of Phytophthora megasperma. Phytopathology, 73(2):129-134

Hansen EM; Maxwell DP, 1991. Species of the Phytophthora megasperma complex. Mycologia, 83(3):376-381; 32 ref.

Hansen MA; Wick RL; Stromberg EL, 1990. First report of Phytophthora megasperma f.sp. glycinea on soybean in Virginia. Plant Disease, 74(2):183

Hartwig EE, 1992. Registration of soybean germplasm line D82-2896 resistant to stem canker and soybean cyst nematode race 3. Crop Science, 32(6):1514; 4 ref.

Henry RN; Kirkpatrick TL, 1995. Two new races of Phytophthora sojae, causal agent of Phytophthora root and stem rot of soybean, identified from Arkansas soybean fields. Plant Disease, 79(10):1074

Herr LJ, 1957. Factors affecting a root rot of soybeans incited by Phytophthora cactorum. Phytopathology, 47:15-16.

Hijano E, 1991. Diseases of lucerne. Boletín INTA - Centro Regional Cuyo, No. 1:20 pp.; 14 ref.

Hildebrand AA, 1959. A root and stalk rot of soybeans caused by Phytophthora megasperma Drechsler var. sojae var. nov. Canadian Journal of Botany, 37:927-959.

Hine RB; Gray FA; Schonhorst MH, 1972. Phytophthora root rot of alfalfa in Arizona. Plant Disease Reporter, 56(6):472-473.

Hoitink HAJ; Schmitthenner AF, 1975. Comparative efficacy of 2-chloro-6-methoxy-4(trichloromethyl)pyridine and ethazole for control of Phytophthora root rot of rhododendron and soybean. Phytopathology, 65(1):69-73

Holub EB; Grau CR, 1990. Ability of Aphanomyces euteiches to cause disease of seedling alfalfa compared with Phytophthora megasperma f.sp. medicaginis. Phytopathology, 80(4):331-335

Holub EB; Grau CR, 1990. Productivity and survival of alfalfa ramets in soil naturally infested with Aphanomyces euteiches and Phytophthora megasperma. Canadian Journal of Plant Pathology, 12(1):83-91

Hsu SC; Lockwood JL, 1984. Biological control of Phytophthora root rot of soybean by Hyphochytrium catenoides in greenhouse tests. Phytopathologische Zeitschrift, 109(2):139-146

Inigo RM, 1973. Clark 63: a new soya-bean variety for Tucuman. Circular Estacion Experimental Agricola de Tucuman, No. 189.

Irwin JAG, 1974. Reaction of lucerne cultivars to Phytophthora megasperma, the cause of a root rot in Queensland. Australian Journal of Experimental Agriculture and Animal Husbandry, 14(69):561-565.

Irwin JAG; Cahill DM; Drenth A, 1995. Phytophthora in Australia. Australian Journal Agricultural Research, 46:1311-1337.

Irwin JAG; Crawford AR; Drenth A, 1996. The origins of Phytophthora species attacking legumes in Australia. Advances in Plant Pathology, 24:432-451.

Irwin JAG; Dales JL, 1982. Relationships between Phytophthora megasperma isolates from chickpea, lucerne and soybean. Australian Journal of Botany, 30(2):199-210

Irwin JAG; Maxwell DP, 1980. Resistance of Medicago species accessions to Phytophthora megasperma f. sp. medicaginis. Plant Disease, 64(4):396-397

Jimenez B; Lockwood JL, 1982. Germination of oospores of Phytophthora megasperma f.sp. glycinea in the presence of soil. Phytopathology, 72(6):662-666

Karakaya A; Gray FA; Koch DW, 1995. Host range and pathogenicity of Phytophthora isolates from kale, tyfon, and alfalfa. Journal of Turkish Phytopathology, 24(3):145-148; 5 ref.

Kaufmann MJ; Gerdemann JW, 1958. Root and stem rot of soybean caused by Phytophthora sojae n.sp. Phytopathology, 48:201-208.

Keen NT; Holliday MJ; Yoshikawa M, 1982. Effects of glyphosate on glyceollin production and the expression of resistance to Phytophthora megasperma f.sp. glycinea in soybean. Phytopathology, 72(11):1467-1470

Kilen TC, 1977. Genetic systems for control of Phytophthora rot of soybeans. In: Proceedings, Annual Soybean Research Conference 7. Washington DC, USA: American Seed Trade Association, 9-15.

Kilen TC; Keeling BL, 1990. Gene frequency changes in soybean bulk populations exposed to Phytophthora rot. Crop Science, 30(3):575-578

Kilen TC; Lambert L, 1994. Registration of D89-9121 soybean germplasm line resistant to foliar feeding insects, phytophthora rot, and stem canker. Crop Science, 34(5):1427

Knights EJ; Southwell RJ; Schwinghamer MW, 2003. Evaluation of wild Cicer species for resistance to Phytophthora root rot. Proceedings of the International Chickpea Conference Raipur, Chhattisgarh, India, 20-22nd January, 54-57.

Kotova VV, 1981. Phytophthora megasperma Drechs. var. sojae Hild., a rare species in the USSR. Mikologiya i Fitopatologiya, 15(4):269-271

Kouyeas H; Chitzanidis A, 1978. Host list of Phytophthora spp. identified in Greece. Phytophthora Newsletter, 6:53-54.

Kovics G, 1980. Identification in Hungary of Phytophthora megasperma var. sojae causing Phytophthora rot in soybean. Novenytermeles, 29(6):515-520

Kovics G, 1981. Occurrence of Phytophthora rot of soybeans in Hungary. Acta Phytopathologica Academiae Scientiarum Hungaricp, 16(1/2):129-132

Kuan T-L; Erwin DC, 1980. Formp speciales differentiation of Phytophthora megasperma isolates from soybean and alfalfa. Phytopathology, 70(4):333-338

Kuan TL; Erwin DC, 1980. Predisposition effect of water saturation of soil on Phytophthora root rot of alfalfa. Phytopathology, 70(10):981-986

Latorre BA; Vargas R; Bartolotti SE, 1992. Phytophthora megasperma var. sojae on asparagus in Chile. Plant Disease, 76(1):101

Laviolette FA; Athow KL, 1977. Three new physiologic races of Phytophthora megasperma var. sojae. Phytopathology, 67(2):267-268

Laviolette FA; Athow KL, 1981. Physiologic races of Phytophthora megasperma f. sp. glycinea in Indiana, 1973-1979. Plant Disease, 65(11):884-885

Layton AC; Kuhn DN, 1988. Heterokaryon formation by protoplast fusion of drug-resistant mutants in Phytophthora megasperma f.sp. glycinea. Experimental Mycology, 12(2):180-194

Leath KT; Baylor JE, 1975. Phytophthora root rot of alfalfa in Pennsylvania. Plant Disease Reporter, 59(12):972-974

Lehman WF; Erwin DC; Stanford EH, 1967. Root rot tolerance in new alfalfa strains now available to plant breeders. California Agriculture, 21(4):6.

Lehman WF; Richards SJ; Erwin DC; Marsh AW, 1968. Effect of irrigation in treatments on alfalfa (Medicago sativa L.) production, persistence, and soil salinity in southern California. Hilgardia, 39:277-295.

Liew ECY; Irwin JAG, 1994. Comparative studies on Phytophthora megasperma isolates from chickpea collected in Australia and Spain. Mycological Research, 98(11):1284-1290

Liew ECY; Irwin JAG, 1997. Differential disease reactions on lucerne genotypes inoculated with Phytophthora medicaginis isolates from lucerne and chickpea. Australian Journal of Agricultural Research, 48(5):545-551; 26 ref.

Liew ECY; Maclean DJ; Irwin JAG, 1998. Specific PCR based detection of Phytophthora medicaginis using the intergenic spacer region of the ribosomal DNA. Mycological Research, 102:73-80.

Lifshitz R; Simonson C; Scher FM; Kloepper JW; Rodrick-Semple C; Zaleska I, 1986. Effect of rhizobacteria on the severity of Phytophthora root rot of soybean. Canadian Journal of Plant Pathology, 8(1):102-106

Lockwood JL; Cohen SD, 1978. Race determination of Phytophthora megasperma var. sojae, using differential soybean varieties inoculated with zoospores or incubated on flooded soil samples. Plant Disease Reporter, 62(12):1019-1921

Lowe KF; Bowdler TM; Gramshaw D; Clem RL; Collyer BG, 1987. Yield, persistence and field disease assessment of lucerne cultivars and lines under irrigation in the Queensland subtropics. Tropical Grasslands, 21(4):168-181.

Majid K; Aslam M; Saleem A, 1992. Root rot of chickpea caused by Phytophthora megasperma var. sojae Drechsler: a new record for Pakistan. Pakistan Journal of Phytopathology, 4(1-2):71

Marks GC; Mitchell JE, 1971. Penetration and infection of alfalfa roots by Phytophthora megasperma and the pathological anatomy of infected roots. Canadian Journal of Botany, 49:63-67.

Masoud SA; Zhu Qun; Lamb C; Dixon RA, 1996. Constitutive expression of an inducible -1,3-glucanase in alfalfa reduces disease severity caused by the oomycete pathogen Phytophthora megasperma f.sp. medicaginis, but does not reduce disease severity of chitin-containing fungi. Transgenic Research, 5(5):313-323; 38 ref.

Matsumoto N; Araki T, 1978. Alfalfa root rot caused by Phytophthora megasperma Drechsler in Japan. Annals of the Phytopathological Society of Japan, 44(2):214-217

Matsumoto N; Sato T, 1985. Host non-specific Phytophthora megasperma with small oogonia from alfalfa-field soil. Research Bulletin of the Hokkaido National Agricultural Experiment Station, No. 143:75-84

McBlain BA; Hacker JK; Zimmerly MM; Schmitthenner AF, 1991. Tolerance to phytophthora rot in soybean: II. Evaluation of three tolerance screening methods. Crop Science, 31(6):1412-1417

McGee DC, 1992. Soybean diseases: a reference source for seed technologists. St Paul, USA; American Phytopathological Society, 151 pp.

McGee DC; Nyvall RF, 1984. Soybean seed health. Coop. Extension Service, Iowa State University, Pm-990.

Michail SH; Abd-El-Rehim MA; Abu Elgasim EA, 1979. Seed health testing of soybean in Egypt. Acta Phytopathologica Academiae Scientiarum Hungaricp, 14(3/4):371-377

Moore KC; Butler BJ, 1979. Root rot resistant lucerne - a big leap forward. Agricultural Gazette of New South Wales, 90(5):36-37

Moots CK; Nickell CD; Gray LE, 1988. Effects of soil compaction on the incidence of Phytophthora megasperma f.sp. glycinea in soybean. Plant Disease, 72(10):896-900

Moots CK; Nickell CD; Gray LE, 1988. Effects of soybean stand reduction and Phytophthora root rot on yield. Plant Disease, 72(10):900-904

Munkvold GP; Carlton WM, 1995. Prevalence and distribution of Aphanomyces euteiches and Phytophthora medicaginis in Iowa alfalfa fields. Plant Disease, 79(12):1251-1253; 27 ref.

Musial JM; Aitken KS; Mackie JM; Irwin JAG, 2005. A genetic linkage map in autotetraploid lucerne adapted to northern Australia, and use of the map to identify DNA markers linked to resistance to Phytophthora medicaginis. Australian Journal of Agricultural Research, 56(4): 333-344.

Myatt PM; Dart PJ; Hayward AC, 1993. Potential for biological control of Phytophthora rootrot of chickpea by antagonistic root-associated bacteria. Australian Journal of Agricultural Research, 44(4):773-784

Nickell CD; Hanson PM; Gray LE; Thomas DJ; Willmot DB, 1990. Registration of soybean germplasm lines LN86-1595 and LN86-1947 resistant to brown stem rot. Crop Science, 30(1):241; 7 ref.

Nickell CD; Schwenk FW, 1980. Registration of Desoto soybean (Reg. No. 132). Crop Science, 20(2):288.

Nickell CD; Thomas DJ; Gray LR; Hanson PM, 1990. Registration of 'Burlison' soybean. Crop Science, 30(1):232

Nugaeva N, 2000. Micromycetes in the substrate and the hyphosphere of Agaricus bisporus. In: Science and cultivation of edible fungi. Proceedings of the 15th International Congress on the Science and Cultivation of Edible Fungi, Maastricht, Netherlands, 15-19 May, 2000 [ed. by Griensven, L. J. L. D. van]. Rotterdam, Netherlands: A.A. Balkema, 417-424.

Nygaard SL; Elliott CK; Cannon SJ; Maxwell DP, 1989. Isozyme variability among isolates of Phytophthora megasperma. Phytopathology, 79(7):773-780

Olah AF; Schmitthenner AF; Walker AK, 1985. Glyceollin accumulation in soybean lines tolerant to Phytophthora megasperma f.sp. glycinea. Phytopathology, 75(5):542-546

Orf JH; MacDonald DH, 1995. Registration of 'Faribault' soybean. Crop Science, 35(4):1227; 10 ref.

Orf JH; Scott RA; Kennedy BW, 1995. Registration of 'Hendricks' soybean. Crop Science, 35(4):1226-1227; 11 ref.

Osburn RM; Milner JL; Oplinger ES; Smith RS; Handelsman J, 1995. Effect of Bacillus cereus UW85 on the yield of soybean at two field sites in Wisconsin. Plant Disease, 79(6):551-556; 36 ref.

Papavizas GC; Lewis JA, 1976. Acetone infusion of pyroxychlor into soybean seed for the control of Phytophthora megasperma var. sojae. Plant Disease Reporter, 60(6):484-488

Peaden RN; Evans DW, Elgin JH Jr. , 1995. Registration of W12SR2W1Fu1 alfalfa germplasm. Crop Science, 35(1):287-288.

Pfeiffer TW, 1994. Registration of 'Calhoun' soybean. Crop Science, 34(5):1411; 4 ref.

Pioneer Hi-Bred International, 1993. Variety: '9582' synonym: 'Soya 582'. Application no. 91/122. Plant Varieties Journal, 6(4):15-16, 35.

Pioneer Hi-Bred International, 1993. Variety: '9791' synonym: 'Soya 791'. Application no. 91/125. Plant Varieties Journal, 6(4):17-18, 35.

Porter DR; Caddel JL; Singleton LL, 1986. Effects of planting dates on expression of Phytophthora root rot resistance of alfalfa. Plant Disease, 70(7):655-657

Pratt RG; Mitchell JE, 1973. Conditions affecting the detection of Phytophthora megasperma in soils of Wisconsin alfalfa fields. Phytopathology, 63(11):1374-1379.

Pratt RG; Mitchell JE, 1975. The survival and activity of Phytophthora megasperma in naturally infested soils. Phytopathology, 65(11):1267-1272

Pulli SK; Tesar MB, 1975. Phytophthora root rot in seedling-year alfalfa as affected by management practices inducing stress. Crop Science, 15:861-864.

Purss GS, 1959. Root rot of lucerne. Queensland Agricultural Journal, 85:767-770.

Rhodes LH; Myers DK, 1989. Effect of seed treatment with metalaxyl or pyroxyfur on damping-off of alfalfa caused by Phytophthora megasperma f.sp. medicaginis. Crop Protection, 8(5):369-372

Ribeiro OK; Erwin DC; Khan RA, 1978. A new high-temperature Phytophthora pathogenic to roots of alfalfa. Phytopathology, 68(2):155-161

Richard C; Martin JG, 1991. Phytophthora root rot of lucerne in Quebec: geographical distribution of symptoms and study of edaphic factors favouring their expression. Phytoprotection, 72(3):87-95

Rogers VE; Irwin JAG; Stovold G, 1978. The development of lucerne with resistance to root rot in poorly prated soils. Australian Journal of Experimental Agriculture and Animal Husbandry, 18(92):434-441

Romero CS, 1978. Tres especies de Phytophthora DeBary de nuevo regisstro en Mexico. Agrociencia, 34:45-55.

Rose JL; Irwin JAG; Ryley MJ; Langdon PW; Jenner LB, 1982. Reaction of soybean cultivars to races of Phytophthora megasperma f.sp. glycinea present in Queensland. Australian Journal of Agricultural Research, 33(5):763-771

Ryley MJ; Mosetter HF; Rose JL, 1989. Yield losses of soybeans due to Phytophthora megasperma f.sp. glycinea. Australian Journal of Agricultural Research, 40(6):1161-1169

Ryley MJ; Obst NR, 1992. Race-specific resistance in soybean cv. Davis to Phytophthora megasperma f.sp. glycinea. Plant Disease, 76(7):665-668

Ryley MJ; Obst NR; Stovold GE, 1991. A new race of Phytophthora megasperma f.sp. glycinea on soybean in Australia. Australasian Plant Pathology, 20(3):97-100

Saleem A; Majeed K; Aslam M; Hamid K; Shahid M; Ali S, 1993. New records of Phytophthora species causing stem/root rot in brinjal, lucerne and soybean in Pakistan. Pakistan Journal of Phytopathology, 5(1-2):131-132

Salvatore MA; Gray FA; Hine RB, 1973. Enzymatically induced germination of oospores of Phytophthora megasperma. Phytopathology, 63:1083-1084.

Schmitthenner AF, 1964. Prevalence and virulence of Phytophthora, Aphanomyces, Pythium, Rhizoctonia, and Fusarium isolated from diseased alfalfa seedlings. Phytopathology, 54:1012-1018.

Schmitthenner AF, 1985. Problems and progress in control of Phytophthora root rot of soybean. Plant Disease, 69(4):362-368

Schmitthenner AF, 1988. Phytophthora rot of soybean. In: Wyllie TD, Scott DH, eds. Soybean Diseases of the North Central Region. St. Paul, USA: American Phytopathological Society, 71-80.

Schmitthenner AF, 1989. Phytophthora root rot: detection, ecology, and control. In: Pascale AJ, ed. World Soybean Research Conference IV Proceedings. Buenos Aires, Argentina: Orientacion Grafica Editora, 1284-1289.

Schmitthenner AF; Van Doren DM, 1985. Integrated control of root rot of soybean caused by Phytophthora megasperma f. sp. glycinea. In: Parker CA, Rovira AD, Moore KJ, Wong PTW, Kollmorgen JF, eds. Ecology and Management of Soilborne Plant Pathogens. St. Paul, USA: American Phytopathological Society, 263-266.

Schmitthenner AF; Walker AK, 1979. Tolerance versus resistance for control of Phytophthora root rot of soybeans. In: Proceedings, Annual Soybean Research Conference, 9. Washington DC, USA: American Seed Trade Association, 35-44.

Schwingle BW; Smith JA; Blanchette RA, 2007. Phytophthora species associated with diseased woody ornamentals in Minnesota nurseries. Plant Disease, 91(1):97-102. HTTP://www.apsnet.org

Shafizadeh S; Kavanagh JA, 2005. Pathogenicity of Phytophthora species and Pythium undulatum isolated from Abies procera Christmas trees in Ireland. Forest Pathology, 35(6):444-450.

Shaw CG, 1973. Host fungus index for the Pacific Northwest. I. Hosts. Bulletin, Washington Agricultural Experimental Station, No. 765.

Silo-Suh LA; Lethbridge BJ; Raffel SJ; He HaiYin; Clardy J; Handelsman J, 1994. Biological activities of two fungistatic antibiotics produced by Bacillus cereus UW85. Applied and Environmental Microbiology, 60(6):2023-2030; 45 ref.

Sinclair JB; Backman PA, 1989. Compendium of Soybean Diseases, 3rd edition. St. Paul, USA: American Phytopathological Society.

Singh SL; Pavgi MS, 1979. Phytophthora root rot of crucifers. Indian Phytopathology, 32(1):129-131

Slusher RL; Sinclair JB, 1973. Development of Phytophthora megasperma var. sojae in soybean roots. Phytopathology, 63:1168-1171.

Smith p; Phillips DV, 1976. Degradation of 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) by Phytophthora megasperma. Journal of Agricultural and Food Chemistry, 24(2):294-295

Sneh B; Humble SJ; Lockwood JL, 1977. Parasitism of oospores of Phytophthora megasperma var. sojae, P.cactorum, Pythium sp., and Aphanomyces euteiches in soil by Oomycetes, Chytridiomycetes, Hyphomycetes, Actinomycetes, and bacteria. Phytopathology, 67(5):622-628

Southwell RJ; Crocker GJ, 2005. Hedysarum - a new susceptible host for Phytophthora medicaginis. Australasian Plant Pathology, 34:265-267.

Stack JP; Millar RL, 1985. Isolation and characterization of a metalaxyl-insensitive isolate of Phytophthora megasperma f.sp. medicaginis. Phytopathology, 75(12):1387-1392

Stack JP; Millar RL, 1985. Relative survival potential of propagules of Phytophthora megasperma f.sp. medicaginis. Phytopathology, 75(12):1398-1404

StMartin SK; Calip-DuBois AJ; Fioritto RJ; Schmitthenner AF; McBlain BA; Cooper RL; Martin RJ, 1995. Registration of 'Sandusky' soybean. Crop Science, 35(1):283-284; 6 ref.

StMartin SK; Calip-DuBois AJ; Fioritto RJ; Schmitthenner AF; McBlain BA; Cooper RL; Martin RJ, 1995. Registration of 'Vertex' soybean. Crop Science, 35(1):284; 5 ref.

Stovold GE; Carratt DE, 1978. Occurrence of Phytophthora megasperma in alfalfa growing soils of New South Wales. Plant Disease Reporter, 62(8):742-744

Stuteville DL; Erwin DC(Editors), 1990. Compendium of alfalfa diseases. Second edition. St. Paul, Minnesota, USA; American Phytopathological Society, 84 pp.

Su YC; Shen CY, 1993. The discovery and biological characteristic studies of Phytophthora megasperma f.sp. glycinea on soyabean in China. Acta Phytopathologica Sinica, 23(4):341-347

Suryanarayana D; Pathak SR, 1968. Foot blight - a new disease of gram. FAO Plant Protection Bulletin, 16:71-73.

Sutherland ED; Lockwood JL, 1984. Hyperparasitism of oospores of some Peronosporales by Actinoplanes missouriensis and Humicola fuscoatra and other actinomycetes and fungi. Canadian Journal of Plant Pathology, 6(2):139-145

Szabó I; Lakatos F, 2008. Phytopthora species isolated from declining forests in Hungary. (Pusztuló erdo?állományokból izolált Phytophthora fajok Magyarországon.) Növényvédelem, 44(12):607-613.

Tachibana H, 1983. Association of Phytophthora root rot of soybean with conservation tillage. Phytopathology, 73:844.

Tachibana H; Epstein AH; Nyvall RF; Musselman RA, 1975. Phytophthora root rot of soybean in Iowa: observations, trends, and control. Plant Disease Reporter, 59(12):994-998

Tachibana H; Hatfield JD; Higley PM, 1983. Phytophthora megasperma var. glycinea suppressive soil of soybean. Phytopathology, 73:823.

Talgø V, 2009. Diseases and disorders on fir (Abies spp.) grown as Christmas trees, boughs, and landscape plants in Norway: from seed to site. As, Norway: Norwegian University of Life Sciences, Department of Plant and Environmental Sciences, 25 pp. + papers I-VII. [Philosophiae Doctor (PhD) Thesis 2009:28.]

Tanaka T, 1982. Difference of resistance of soyabean varieties to several isolates of stem rot Phytophthora and pathogenic races of isolates. Annual Report of the Society of Plant Protection of North Japan, No.33:72-74

Thomison PR; Thomas CA; Kenworthy WJ, 1987. Genotype-race interactions in relation to Phytophthora rot of soybean. Soybean Genetics Newsletter, 14:273-276

Thomison PR; Thomas CA; Kenworthy WJ; McIntosh MS, 1988. Evidence of pathogen specificity in tolerance of soybean cultivars to Phytophthora rot. Crop Science, 28(4):714-715

Thompson AH, 1987. Phytophthora root rot of lucerne in the Transvaal, South Africa. Phytophylactica, 19(3):319-322

Thompson AH, 1988. Phytophthora root rot of lucerne in the Cape Province, South Africa. Phytophylactica, 20(2):181-182

Tooley PW; Grau CR, 1984. The relationship between rate-reducing resistance to Phytophthora megasperma f.sp. glycinea and yield of soybean. Phytopathology, 74(10):1209-1216

Tooley PW; Grau CR; Stough MC, 1982. Races of Phytophthora megasperma f.sp. glycinea in Wisconsin. Plant Disease, 66(6):472-475

Tooley PW; Stough MC; Grau CR, 1979. The association of Phytophthora megasperma var. sojae races with soybean in Wisconsin. Phytopathology, 69(9):1047.

Trapero-Casas A; Rodriquez-Tello A; Kaiser WJ; Jimenez-Diaz RM, 1992. Seedling blight and root rot of chickpea caused by Phytophthora megasperma in Spain. 2nd International Food Legume Research Conference, 12-14 April, Cairo, Egypt.

Tsuchiya S, 1982. Occurrence of soybean stem rot caused by Phytophthora megasperma var. sojae Hildebrand in Hokkaido. Bulletin of Hokkaido Prefectural Agricultural Experiment Stations, No. 48:46-55

Tsuchiya S; Tanaka F; Kodama F, 1982. Resistance of some soyabean cultivars to Phytophthora megasperma var. sojae Hildebrand and pathogenic race of isolates. Annual Report of the Society of Plant Protection of North Japan, No. 33:69-71

Tu JC, 1980. Incidence of root rot and overwintering of alfalfa as influenced by rhizobia. Phytopathologische Zeitschrift, 97(2):97-108

Tyler BM; Forster H; Coffey MD, 1995. Inheritance of avirulence factors and restriction fragment length polymorphism markers in outcrosses of the oomycete Phytophthora sojae. Molecular Plant-Microbe Interactions, 8(4):515-523

Vaartaja O; Pitblado RE; Buzzell RI; Crawford LG, 1979. Chemical and biological control of Phytophthora root and stalk rot of soybean. Canadian Journal of Plant Science, 59(2):307-311

Vandemark GJ; Barker BM, 2003. Quantifying Phytophthora medicaginis in susceptible and resistant alfalfa with a real-time fluorescent PCR assay. Journal of Phytopathology, 151(11/12): 577-583.

Vincelli P; Nesmith WC; Eshenaur BC, 1994. Incidence of Aphanomyces euteiches and Phytophthora medicaginis in Kentucky alfalfa fields. Plant Disease, 78(6):645-647

Vock NT; Langdon PW; Pegg KG, 1980. Root rot of chickpea caused by Phytophthora megasperma var. sojae in Queensland. Australasian Plant Pathology, 9(4):117

Voldeng HD; Saindon G, 1991. Registration of a high-protein soybean germplasm line OT89-16. Crop Science, 31(4):1100.

Wagner RE; Wilkinson HT, 1992. A new physiological race of Phytophthora sojae on soybean. Plant Disease, 76(2):212

Walker AK; Schmitthenner AF, 1982. Developing soybean varieties tolerant to Phytophthora rot. In: Proceedings, Annual Soybean Research Conference, 12. Washington DC, USA: American Seed Trade Association, 67-78.

Walker AK; Schmitthenner AF, 1984. Heritability of tolerance to Phytophthora rot in soybean. Crop Science, 24(3):490-491

Ward EWB, 1984. Suppression of metalaxyl activity by glyphosate: evidence that host defence mechanisms contribute to metalaxyl inhibition of Phytophthora megasperma f.sp. glycinea in soybeans. Physiological Plant Pathology, 25(3):381-386

Ward EWB, 1989. Susceptibility of immature soybean leaves to Phytophthora species. Physiological and Molecular Plant Pathology, 34(5):393-402

Ward EWB; Cahill DM; Bhattacharyya MK, 1989. Abscisic acid suppression of phenylalanine ammonia-lyase activity and mRNA, and resistance of soybeans to Phytophthora megasperma f.sp. glycinea. Plant Physiology, 91(1):23-27

Ward EWB; Cahill DM; Bhattacharyya MK, 1989. Early cytological differences between compatible and incompatible interactions of soybeans with Phytophthora megasperma f.sp. glycinea. Physiological and Molecular Plant Pathology, 34(3):267-283

Ward EWB; Lazarovits G, 1982. Temperature-induced changes in specificty in the interaction of soybeans with Phytophthora megasperma f.sp. glycinea. Phytopathology, 72(7):826-830

Ward EWB; Lazarovits G; Stossel P; Barrie SD; Unwin CH, 1980. Glyceollin production associated with control of Phytophthora rot of soybeans by the systemic fungicide, metalaxyl. Phytopathology, 70(8):738-740

Waterhouse GM, 1963. Key to the species of Phytophthora de Bary. Mycological Papers (CMI), 92:1-22.

Wehrmann VK; Fehr WR; Cianzio SR, 1988. Analysis of strategies for transfer of an allele for resistance to Phytophthora rot in soybean. Crop Science, 28(2):248-250

Welty RE; Busbice TH, 1976. Phytophthora root rot of alfalfa in North Carolina. Plant Disease Reporter, 60(1):14-18

Whisson SC; Maclean DJ; Manners JM; Irwin JAG, 1992. Genetic relationships among Australian and North American isolates of Phytophthora megasperma f.sp. glycinea assessed by multicopy DNA probes. Phytopathology, 82(8):863-868

Wiersma DW; Grau CR; Undersander DJ, 1995. Alfalfa cultivar performance with differing levels of resistance to Phytophthora and Aphanomyces root rots. Journal of Production Agriculture, 8(2):259-264

Wiersma DW; Undersander DJ; Grau GR, 1997. Root heave of alfalfa cultivars with differing levels of resistance to aphanomyces root rot. Agronomy Journal, 89(1):148-150; 18 ref.

Wilcox JR; Ferris JM; Faghihi J; Abney TS, 1995. Registration of 'Bronson' soybean. Crop Science, 35(4):1207-1208; 5 ref.

Wilcox WF; Mircetich SM, 1987. Lack of host specificity among isolates of Phytophthora megasperma. Phytopathology, 77(8):1132-1137

Wilkinson HT; Millar RL, 1981. Phytophthora root rot of alfalfa in central New York. Plant Disease, 65(2):127-129

Wilkinson HT; Millar RL, 1982. Effects of soil temperature and moisture on activity of Phytophthora megasperma f.sp. medicaginis and Alfalfa root rot in the field. Phytopathology, 72(7):790-793

Williams C; Marshall JG; Rabb JL; Davis JH; Sloane LW; Phillips SA; Trahan GJ, 1972. Louisiana soybean variety trials, 1968-1971. Bulletin Agricultural Experiment Station Louisiana State University, No. 666.

Xiao K; Kinkel LL; Samac DA, 2002. Biological control of Phytophthora root rots on alfalfa and soybean with Streptomyces. Biological Control, 23(3):285-295; 47 ref.

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