Heterodera cajani (pigeon pea cyst nematode)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Risk of Introduction
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Growth Stages
- List of Symptoms/Signs
- Biology and Ecology
- Natural enemies
- Notes on Natural Enemies
- Means of Movement and Dispersal
- Seedborne Aspects
- Pathway Vectors
- Plant Trade
- Detection and Inspection
- Similarities to Other Species/Conditions
- Prevention and Control
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Heterodera cajani Koshy, 1967
Preferred Common Name
- pigeon pea cyst nematode
Other Scientific Names
- Heterodera vigni Edward & Misra, 1968
- HETDCJ (Heterodera cajani)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Metazoa
- Phylum: Nematoda
- Class: Secernentea
- Order: Tylenchida
- Family: Heteroderidae
- Genus: Heterodera
- Species: Heterodera cajani
Notes on Taxonomy and NomenclatureTop of page This nematode is included in the genus Heterodera because of the formation of characteristic lemon-shaped cysts with a protruding terminal vulval cone. It was recorded as Heterodera trifolii by Swarup et al. (1964) and later considered and described as a new species, H. cajani by Koshy (1967) from Cajanus cajan (pigeon pea). Edward and Misra (1968) described Heterodera vigni from the roots of Vigna unguiculata which was later synonymized with H. cajani by Kalha and Edward (1979).
DescriptionTop of page The morphology of H. cajani has been described by Koshy (1967), Edward and Misra (1968), Koshy et al. (1971) and Shahina and Maqbool (1995). Identification of 39 species of Heterodera, including H. cajani, is based on terminal cone structures of cysts and a key to species is given by Mulvey (1972).
After Koshy (1967), original description:
15 females: L=0.68-0.94 mm; width="0".363-0.488 mm; L/W ratio=1.4-2.1; stylet=20-30 µm.
25 cysts: L=0.32-0.85 (0.625) mm; width="0".206-0.565 (0.373) mm; L/W ratio=1.65.
18 males: L=0.844-1.666 (1.04) mm; stylet=23-29 (26) µm; spicules=32-43 (36) µm.
18 second-stage juveniles (J2): L=0.275-0.456 (0.392) mm; a=22-23; b=2.6-3.1; c=7-10; stylet=20-25 (23) µm; tail=39-54 (42) µm; tail hyaline portion=14-34 (24) µm.
After Koshy and Swarup (1971c):
6 second-stage juveniles (J2): L=0.344-0.515 (0.435) mm; a=18.3-28.9 (23.9); b=3.2-5.3 (4.1); b'=2.5-3.7 (3.1); c=8.0-12.3 (9.7); stylet=23-27 (25) µm; tail=32-52 (45) µm; hyaline tail terminus=17-30 (24) µm.
6 early third-stage juveniles: L=0.35-0.40 (0.37) mm; a=6.7-8.6 (8); b=?; b'=3.8-4.9 (5); genital primordium=19-66 (16-22) µm.
5 fourth-stage female juveniles: L=0.35-0.42 (0.38) mm; a=2.6-5.1 (3.8); b=?; c=38.0-39.7 (38.8); V=66.7-73.7 (70.2).
5 fourth-stage male juveniles: L=0.33-0.36 (0.35) mm; a=4-5.
After Edward and Misra (1968) for Heterodera vigni [H. cajani]:
20 females: L=0.350-0.625 (0.462) mm; width="0".125-0.370 (0.232) mm; stylet=20-23 (21.5) µm.
100 cysts: L=0.45-0.69 (0.56) mm; width="0".29-0.45 (0.38) mm; stylet=20-23 (21.5) µm.
15 males: L=1.05-1.24 mm; a=38-44; b=7.5-10; c=150-280; stylet=22-25 µm; spicules=28-30 µm; gubernaculum=8-10 µm.
100 eggs: L=95-115 (110) µm; width 37-48 (43) µm.
100 second-stage juveniles (J2): L=0.35-0.51 (0.44) mm; a=23-30; b=3.5-3.9; c=9-10; stylet=18-22 (21.3) µm.
Body obese, lemon-shaped and white to slightly brown, with a neck and posterior cone-like elevation on which the vulva is situated; turns into a cyst of same size and shape. Posterior part of body protruding outside the root usually with small rounded egg sac attached to it. Cephalic region with two annules, the second larger than the first. Stylet of medium strength, in two equal parts; basal knobs round to slightly anteriorly flattened. Median oesophageal bulb large rounded, with well developed valve plates. The excretory pore is placed posterior behind the median bulb. Oesophageal glands extend over the intestine. Ovaries paired, convoluted. Uterus with several eggs filling most of the body. Vulva a large transverse slit on a cone-shaped elevation of the body. Anus close to vulva. An egg sac is present.
Lemon-shaped, with protruding neck and vulva region, light-brown, thin walled and without a subcrystalline layer. Cuticle surface with a zigzag pattern. Vulval cone is prominent. Vulval slit fairly long, terminal. The end-on view of the vulval cone shows concentric wavy lines of cuticular ridges around the vulval slit and two large fenestrae. Ambifenestrate with the two semifenestrae separated by a vulval bridge and surrounded by a wide 'basin'. Anus indistinct. Bullae present, few. The underbridge is simple, thin.
Size varies between 0.5-2 times the size of cyst (note that other species of the schachtii group have egg sacs not more than one cyst size). Yellow, occasionally purple. Few to 200 eggs (average 54) are found in the egg sacs (Koshy and Swarup, 1971c).
Oval, 95-115 (110) µm long, 37-48 (43) µm wide. Egg shell hyaline, without surface markings.
Morphological characteristics of 2nd-, 3rd- and 4th-stage juveniles of H. cajani, H. avenae and H. mothi are described and compared by Taya and Bajaj (1986).
Second-stage juveniles (J2): vermiform, tapering at both ends, assuming a slightly arcuate position when relaxed or dead. Cephalic region with 3-4 annules and an indistinct labial disc. Cephalic framework strongly sclerotized. Cuticle distinctly annulated. Lateral field with four incisures forming three bands; middle band distinct and narrower than the outer ones. Stylet strong, 17-23 µm long, with flattened to anteriorly directed knobs; dorsal knob larger than the subventrals. Dorsal oesophageal gland orifice 3-4 µm from the base of the stylet. Median oesophageal bulb oval, muscular, with distinct cuticular thickenings. Oesophageal glands elongate, extending over intestine mostly ventrally; subventral glands larger and extending past the dorsal gland. Nerve ring encircling isthmus a little behind the median bulb. Excretory pore just behind the level of the nerve ring. Hemizonid just anterior to excretory pore. Tail elongate-conoid, usually 35-45 µm long, with a small rounded terminus; hyaline region more than half tail length. Phasmids small, pore-like, about one anal body width behind anus level.
Common, found in egg masses or in soil. Body ventrally arcuate to open C-shaped when relaxed. Lateral field with four incisures, one-fourth to one-third as wide as body. Cephalic region slightly offset from body contour, with four annules and an indistinct labial disc, framework heavily sclerotized. Median oesophageal bulb oval, muscular, with distinct inner cuticular thickenings. Isthmus short, encircled by nerve ring. Oesophageal glands extending over intestine mostly ventrally and ventro-laterally; dorsal gland nucleus larger and anterior to those of subventral glands. Oesophago-intestinal valve indistinct, about 1-1.5 body widths from centre of median bulb. Hemizonid distinct, 1-2 annules long, about one corresponding body width behind oesophago-intestinal junction. Excretory pore 140-160 µm from anterior end of body, 5-7 annules behind hemizonid. Testis single, anteriorly outstretched. Spicules paired, similar, cephalated, slightly arcuate ventrally, notched terminally, 26-29 µm long. Gubernaculum linear, 8-10 µm long. Tail end bluntly convex-conoid; tail short, less than one anal body width.
DistributionTop of page H. cajani is widely distributed in India. The references cited in the list provide the results of some detailed surveys.
Distribution TableTop of page
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.
Risk of IntroductionTop of page H. cajani is found mainly in India and Pakistan and has a limited distribution in Egypt. Quarantine measures are recommended against this and other cyst nematodes (Mathur, 1986).
HabitatTop of page Adults, cysts, juveniles and eggs of H. cajani are associated with roots or surrounding soil.
Hosts/Species AffectedTop of page Of the 105 species of plants belonging to 58 genera in 21 families tested, only 19 (18 in Fabaceae and Sesamum indicum in Pedaliaceae) proved to be hosts. Pigeon pea (Cajanus cajan), Lablab purpureus, Vigna radiata, cowpea (V. unguiculata) and sesame (Sesamum indicum) were the most favoured hosts and showed extensive damage from H. cajani attack (Koshy and Swarup, 1973).
Reports of primary hosts include C. cajan, V. unguiculata, Vigna mungo, V. radiata, V. aconitifolia, Phaseolus species, Pisum sativum and Phyllanthus maderaspatensis (Evans and Rowe, 1998); S. indicum and Cyamopsis tetragonoloba from Haryana (India) (Bhatti and Gupta, 1973).
Other host reports are of L. purpureus, S. indicum, Sesbania aculeata [S. bispinosa] and Crotalaria juncea (Walia et al., 1985); Cyamopsis tetragonoloba, V. radiata and V. mungo (Yadav and Walia, 1989); Phaseolus vulgaris, Sesbania bispinosa and V. radiata as winter host plants (Jain et al., 1994a); species of Atylosia, Dunbaria, Flemingia and Rhynchosia (Sharma and Nene, 1985); and V. mungo (Kalha and Edward, 1979).
Three biological races with different host preferences have been distinguished by Siddiqui and Mahmood (1993).
Host Plants and Other Plants AffectedTop of page
|Cajanus cajan (pigeon pea)||Fabaceae||Main|
|Crotalaria juncea (sunn hemp)||Fabaceae||Other|
|Cyamopsis tetragonoloba (guar)||Fabaceae||Main|
|Lablab purpureus (hyacinth bean)||Fabaceae||Main|
|Phaseolus vulgaris (common bean)||Fabaceae||Main|
|Pisum sativum (pea)||Fabaceae||Main|
|Sesamum indicum (sesame)||Pedaliaceae||Main|
|Sesamum malabaricum||Pedaliaceae||Wild host|
|Sesbania cannabina (corkwood tree)||Fabaceae||Other|
|Vigna aconitifolia (moth bean)||Fabaceae||Main|
|Vigna mungo (black gram)||Fabaceae||Main|
|Vigna radiata (mung bean)||Fabaceae||Main|
|Vigna unguiculata (cowpea)||Fabaceae||Main|
Growth StagesTop of page Flowering stage, Fruiting stage, Pre-emergence, Seedling stage, Vegetative growing stage
SymptomsTop of page The symptoms of nematode injury include stunting, reduced leaf lamina size and yellowing on cotyledonary leaves (Gaur and Singh, 1977). Flowers and pods are reduced in size and number and the root system may also be poorly developed. Sharma (1993) cautions that foliage symptoms are generally not apparent even in heavily infested soils, but a reduction in height and vigour of the infected plants can be discerned by careful comparison with healthy plants. The disease is recognized by the presence of pearly white females on roots or brown cysts in the soil.
List of Symptoms/SignsTop of page
|Fruit / reduced size|
|Leaves / abnormal colours|
|Roots / cysts on root surface|
|Roots / reduced root system|
|Stems / stunting or rosetting|
|Whole plant / dwarfing|
Biology and EcologyTop of page
The development and life cycle of H. cajani were studied by Koshy and Swarup (1971c) on pigeon pea plants at an average soil temperature of 29°C (range 27-36°C). Second-stage juveniles (J2) penetrate the roots within 48 hours of inoculation. Both tap and lateral roots were penetrated, not necessarily near the root tips. Moulting began on the third day beginning from the anterior part and completing on the fourth day. Fourth-stage juveniles with well-developed reflexed ovaries were found on the tenth day. Adult lemon-shaped females were observed on the 12th day. Males were found on the 12th or 13th day. On the 14th day, many eggs were seen in the egg sacs as well as inside the white females. Second-stage juveniles were collected from soil as well as from cysts from which they hatched on the 16th day. A few males, apparently embedded in the egg mass, also emerged from the cysts. The white females turned yellowish from the 20th day onwards; the change from white to bright yellow took 8 days. The egg sac turned opaque and yellowish, occasionally purple. Brown cysts were noticed on the 38th day after inoculation. Although males are thought to be necessary for reproduction, females sometimes reproduced without them.
The life cycle was completed in 16 days at 29°C but during cooler conditions (10-25°C), the life-cycle took 45-80 days to complete (Koshy and Swarup, 1971c). On one crop of pigeon pea, 8-9 generations were recorded. Kalha and Edward (1979) studied the life cycle in Phaseolus mungo [Vigna mungo]. They found that juveniles took 3 days to penetrate the root and developed into males and females in 24 and 27 days, respectively.
Yadav and Walia (1989) found that H. cajani completes its life cycle on pigeon pea and Vigna aconitifolia in 23 days; on Vigna radiata in 26 days and on V. mungo and cowpea (V. unguiculata) in 29 days at a temperature of 24-39°C. On cowpea, Gupta and Edward (1974) found that the total time required by H. cajani to complete one generation was 13 days for males and 17 days for females and that in one growth season of the host lasting approximately 4 months, the nematode could produce up to 8 generations. As many as nine generations could be completed in 1 year under laboratory conditions. Two favourable periods for the multiplication of the nematode were during June-September and April-June in North India (Koshy and Swarup, 1971d).
A life table for H. cajani on pigeon pea at 25°C was developed by Singh and Sharma (1995b). Mortality rates were very high during egg and J2 stages prior to root penetration. Mortality of subsequent life stages was low and virtually constant. Egg laying began on the 23rd day and stopped on the 31st day after the start of the cohort. Mean generation time was 26.9 days and net reproductive rate 15.5 times per generation. The true intrinsic rate (rm) of natural increase indicated that a H. cajani population would multiply 1.107 times a day, and double itself in about 7 days.
Development and reproduction
H. cajani is primarily a parasite of roots. The adult females are lemon-shaped and sedentary in habit, and remain attached to roots semi-endoparasitically. Males are vermiform. Eggs may be retained inside the female body but many are laid in a gelatinous matrix forming egg sacs.
The optimum soil moisture content required for the development of H. cajani is between 35 and 45%. The number of cysts and final nematode population were higher when plants were irrigated twice in 24 h than once in either 24 or 48 h (Sharma and Trivedi, 1997). In pigeon pea, nematode multiplication is highest in sand and sandy loam soils due to the better development of plant roots (Walia, 1987).
Singh and Sharma (1994) studied the effects of constant and fluctuating temperatures on the development and reproduction of H. cajani on pigeon pea in growth chambers at 10, 15, 20, 25 and 30°C and in a greenhouse fluctuating between 22 and 38°C. Nematode penetration was greatest in roots at 25°C; there was no penetration at 10°C. The basal threshold temperature for development was calculated to be 11°C. Completion of one H. cajani generation required 17, 28, 35 and 66 days (323, 392, 315 and 264 degree-days) at 30, 25, 20 and 15°C, respectively, and 19 days (356 degree-days) at a fluctuating temperature. Survival was greater at 20 and 25°C than at 15 and 30°C. The greatest number of females (18 females per root) was produced at 25° females at 15°C. Nematode reproduction was 1.6 to 7.1 times greater at 25°C than at other temperatures. Equations were developed to predict nematode development rate, cumulative juvenile emergence from egg sacs and cysts, and population increases as influenced by temperature. Singh and Sharma (1995a) found that averaged across temperatures (20-32°C), the percentage of juveniles that penetrated roots was 34, 32, 9 and 4% at 24, 32, 16 and 40% soil moisture levels, respectively. Numbers of females per root system 4 weeks after infesting soil with J2 was 80 at 24%, 65 at 32%, 26 at 16%, and 39 at 40% soil moisture. Nematode reproduction was greatest at 24% soil moisture and 25°C. The Reproductive Factor was 19.4 at 24%, 15.2 at 32%, 5.7 at 16%, and 0.5 at 40% soil moisture level. Nematode penetration, development, and reproduction at different moisture levels were greater at 25 and 25-32° was retarded at 40% soil moisture and 20°C compared with that at 24 and 32% moisture levels and 25°C (Singh and Sharma, 1995a).
Yadav and Walia (1989) showed that larval penetration and multiplication was higher on pigeon pea, Sesbania bispinosa and Lablab purpureus than on cowpea, Vigna aconitifolia, Cyamopsis tetragonoloba and sesame. The fecundity of the nematode was not affected by the host.
Factors affecting the emergence of juveniles were studied by Koshy and Swarup (1971b) and reviewed by Sharma and Sharma (1998).
Emergence from egg sacs is higher and more rapid than from white (young) or brown (mature) cysts (Sharma and Swarup, 1984; Sharma and Sharma, 1998). From white cysts, 50-80% of the juveniles emerged within 1 month at 25-30°C. 53% of the juveniles from brown cysts emerged at 25°C, 52% at 20°C and 5% at 15°C. About 48% of the juvebiles did not emerge even after incubation for 525 days at 25°C. These dormant juveniles were either free or within eggs in cysts. Juvenile emergence was greater from cysts produced on 30-day-old pigeon pea plants than from cysts produced on older plants. The pattern of J2 emergence in H. cajani is complex and temperature is a major, but not the only, important factor. Some of the encysted juvenile population undergoes diapause (Singh and Sharma, 1996).
No emergence occurs at 12 and 40°C. At fluctuating temperatures (15-40°C), the emergence of juveniles occurs in phases: 70-90% juveniles emerged in 5-7 months, followed by a short dormancy period of 2-4 months (Sharma and Swarup, 1984). It has been suggested that the nematodes have mechanisms of temperature-, host- and time-mediated delays which must have evolved gradually but have persisted because of their survival value (Singh and Sharma, 1996). Aeration does not appear to affect larval emergence but cysts exposed to light result in higher emergence than the cysts subjected to total darkness. Emergence occurs over a wide pH range, from 3.5-11.5; optimum at pH 10.5 (Singh and Sharma, 1996).
Hatching from cysts and egg sacs of six successive generations of H. cajani produced on cowpea during a single growing season in the greenhouse was compared in distilled water, soil leachate and host root diffusate by Gaur et al. (1992). Hatch from cysts but not egg sacs in the fifth and sixth generations, produced on senescing plants, showed a marked dependency on host root diffusate. The ratio of eggs in egg sacs to eggs in cysts decreased with each succeeding generation and a comparison between third and sixth generations indicated that, in the older generation, more lipid reserves are partitioned into the encysted J2 than into the J2 in egg sacs (Gaur et al., 1992).
Root leachates of host plants stimulated the larval hatch of H. cajani. Leachates collected from 2, 3 or 4-week-old plants or soil were more stimulatory than those from 1-week-old plants (Yadav and Walia, 1989).
Eggs within cysts are able to withstand extremes of desiccation; a maximum reduction of about 30% of viable eggs was recorded after 3 weeks exposure to 0% relative humidity (RH), which is similar to the reduction found in dry soil after storage of between 2 and 12 months. Cysts stored in moist soil for up to 12 months gave a greater percentage hatch in cowpea root diffusate (CRD) than those from air dried soil but the actual number of J2 emerging per cyst was lower. Eggs hatched during the first 4 months of storage in moist soil but only during the first 2 months in air dried soil (Gaur et al., 1996).
H. cajani juveniles were observed in the cortex of pigeon pea seedlings 48 h after inoculation. Movement was predominantly intracellular. Syncytia formed in the stelar region. Cells near the feeding site became angular with thickened cell walls. Giant cells had dense granular cytoplasm with 4-5 nuclei. There was extensive disruption of the xylem vessels. Juveniles which were established in the cortex developed mostly into males and those in the stelar region into females (Koshy and Swarup, 1980).
In glasshouse pot experiments with pigeon pea (Cajanus cajan), an initial density of 1.0 juvenile per cm³ soil resulted in a 14-24% reduction in plant height, root and shoot mass and leaf area. The tolerance limit for pod yield in field experiments was 2.6 eggs and juveniles of H. cajani per cm³ soil at sowing time (Sharma et al., 1993b).
H. cajani caused a reduction in bacterial nodule weight in Cyamopsis tetragonoloba at inoculum levels of 500 juveniles/plant and above. However, the actual functioning of the nodules was reduced at inoculum levels of 5 juveniles/plant and above. It is suggested that H. cajani infection causes an accumulation of ammonia in the roots of C. tetragonoloba leading to inactivation of nitrogenase and, consequently, a reduction in nitrogen fixation (Walia et al., 1989).
Various pathogenicity studies looking at plant growth parameters have been carried out on:
Vigna mungo (Devi and Gupta, 1988; Jain et al., 1994b); pigeon pea (Zaki and Bhatti, 1986c; Walia, 1987; Devi and Gupta, 1988; Sharma and Nene, 1988; Singh and Singh, 1995); sesame (Rana and Dalal, 1994);
cowpea (Aboul-Eid and Ghorab, 1974; Zaki and Bhatti, 1986c; Devi and Gupta, 1988); V. radiata (Devi and Gupta, 1988); V. aconitifolia (Zaki and Bhatti, 1986c); and Cyamopsis tetragonoloba (Walia and Bhatti, 1989).
The effects of H. cajani infestation on nitrogen, phosphorus and potassium levels in the roots and tops of pigeon pea and V. aconitifolia seedlings were studied by Zaki and Bhatti (1986b) and on the sugar content of Vigna sinensis [V. unguiculata] by Sethi and Sharma (1978) and Sharma and Sethi (1979a).
Fourteen populations of H. cajani from different localities in seven districts of Uttar Pradesh (India) were tested on 9 hosts revealing the presence of 3 races: Race 1 reproduced on all the hosts tested; Race 2 did not reproduce on Cyamopsis tetragonoloba; Race 3 did not reproduce on C. tetragonoloba or Crotalaria juncea (Siddiqui and Mahmood, 1993).
Interactions with other plant pathogens
Interactions between H. cajani and the following pathogens have been studied:
Fusarium udum [Gibberella indica], on pigeon pea (Sharma and Nene, 1989; Singh et al., 1993c; Rai and Singh, 1996b; Siddiqui and Mahmood, 1999);
Fusarium solani, on cowpea (Varaprasad et al., 1987; Varaprasad and Kumar, 1991);
Rhizoctonia bataticola [Macrophomina phaseolina] (Walia and Gupta, 1986b), on Vigna mungo (Tiwari, 1998);
Rhizoctonia solani [Thanatephorus cucumeris], on cowpea (Walia and Gupta, 1986a);
Meloidogyne incognita, on pigeon pea (Siddiqui and Mahmood, 1999); on cowpea (Sharma and Sethi, 1976, 1978a, 1979b).
Natural enemiesTop of page
|Natural enemy||Type||Life stages||Specificity||References||Biological control in||Biological control on|
Notes on Natural EnemiesTop of page Juveniles of H. cajani have been found to be naturally infected by the bacterium Pasteuria penetrans; a 27% reduction in the number of juveniles in roots and the maximum reduction in cyst population were obtained when spore-infected soil was incubated at 30°C before application to cowpea seedlings infested with H. cajani (Bhattacharya and Swarup, 1989). The number of cysts and J2 of the nematode decreased significantly in pot treatments receiving combined inoculations of H. cajani and P. penetrans, compared with the treatment receiving H. cajani alone; maximum reductions were 61 and 87% in cyst and J2 populations, respectively. Cyst infection increased from 6% at the harvest of the first planting to 50% at the harvest of the third planting. Average number of eggs per cyst also decreased significantly at the harvest of each planting in the presence of P. penetrans.
All the plant growth characters, except root length, increased significantly at the harvest of the second planting in treatments receiving H. cajani and P. penetrans together compared with H. cajani alone. The damage caused by H. cajani was completely offset by P. penetrans at the harvest of the third planting and the growth was on a par with the control which included neither pathogen. In India, the phenomenon of host specificity among strains of Pasteuria from cyst nematodes suggests complexity of taxa within this group (Kahn and Saxena, 1995). A sticky swarm disease of H. cajani and Meloidogyne javanica caused by P. penetrans has been reported by Sharma and Sharma (1989).
Females of H. cajani, dislodged from roots of its hosts, were highly susceptible to the fungus Catenaria anguillulae. The fungus grew in the living females and males, causing paralysis of the invaded portion of the nematode body. Clearly, the fungus is a virulent parasite of nematodes (Singh et al., 1996). Within 30 minutes of inoculation with C. anguillulae on to the immobilized juveniles of H. cajani, 8-12 smaller globules rearranged in circular forms, followed by half-moon shapes 17 minutes later; zoospore differentiation, vesicle formation and release of zoospores occurred within 50 minutes of the half-moon stage (Singh et al., 1993a).
In pot experiments, Glomus mosseae, Paecilomyces lilacinus and Pseudomonas fluorescens were investigated for control of the wilt disease complex of pigeon pea caused by H. cajani and F. udum [Gibberella indica]. All three antagonists, alone or in combination, increased plant growth, nodulation, phosphorus contents and reduced nematode multiplication and wilting in infected plants (Siddiqui et al., 1998b). P. lilacinus at 1 or 2 g/kg soil together with carbosulfan seed treatment resulted in lower H. cajani populations and higher Vigna radiata growth and yield compared with untreated controls (Rana and Dalal, 1995).
Bacillus subtilis and B. pumilus show potential for killing juveniles of H. cajani, H. zeae and H. avenae. B. cereus and two Pseudomonas species are also larvicidal (Gokte and Swarup, 1989). In glasshouse experiments on Vigna mungo, culture filtrate of B. subtilis reduced cyst and juvenile populations by 95 and 94%, respectively, followed, at lower levels, by Pseudomonas fluorescens and P. lilacinus (Latha and Sivakumar, 1998).
Prior addition of Rhizobium (by 2 weeks) enhanced nodulation and reduced nematode reproduction on Vigna radiata. However, on Cyamopsis tetragonoloba, prior addition of Rhizobium enhanced reproduction of the nematode (Dalal and Bhatti, 1996).
Cephalosporium species, Fusarium solani, Fusarium species and Glomus species have also been found in cysts of H. cajani. In water agar, F. solani infected 70% of eggs in egg sacs and, in greenhouse tests, the number of eggs was reduced by 45-60% (Singh et al., 1997).
Means of Movement and DispersalTop of page Spread of H. cajani by itself is limited. Transportation results mainly from flooding, drainage or transfer of infested seeds and plants, from soil washings, and from soil attached to farm machinery, livestock, tools or people (Mathur, 1986; Sharma, 1998). Every effort should therefore be taken to ensure the prevention of transport of infested material to hitherto uninfested areas and to maintain high standards of sanitation.
Seedborne AspectsTop of page The disease caused by H. cajani is not seedborne. However, cysts containing eggs and egg masses may contaminate the seeds and thus spread the infection.
Pathway VectorsTop of page
Plant TradeTop of page
|Plant parts liable to carry the pest in trade/transport||Pest stages||Borne internally||Borne externally||Visibility of pest or symptoms|
|Fruits (inc. pods)||cysts||Yes||Pest or symptoms usually invisible|
|Leaves||cysts||Yes||Pest or symptoms usually invisible|
|Seedlings/Micropropagated plants||cysts||Yes||Pest or symptoms usually invisible|
|Stems (above ground)/Shoots/Trunks/Branches||cysts||Yes||Pest or symptoms usually invisible|
|True seeds (inc. grain)||cysts||Yes||Pest or symptoms usually invisible|
ImpactTop of page In India, H. cajani is considered to be one of the four most important cyst nematodes and is an economic pest of cowpea and pigeon pea. Although accurate estimates of economic crop loss are not available, yield reduction and decline of plants have been reported by many workers such as Sharma (1993), who recorded yield losses in pigeon pea of over 30%.
H. cajani infection suppresses plant growth of pigeon pea by 28% and reduces grain yield by 24%; in mung bean (Vigna radiata), plant growth was suppressed by 42% and grain yield by 68% (Saxena and Reddy, 1987). When H. cajani is associated with the fungus Fusarium udum [Gibberella indica] there is a significant increase in wilting (Hasan, 1984).
DiagnosisTop of page Sieving, Fenwick-can and modified Fenwick-can are the best techniques for extracting H. cajani cysts. Use of a 80-µm mesh aperture sieve is recommended over a 60-µm mesh sieve for isolating all cyst sizes (Sharma and Nene, 1986). For separation of cysts from debris, organic liquids such as acetone or acetone carbon are better than inorganic/sugar solutions. Best hatching, however, is obtained from cysts recovered from sugar flotation (Rajan and Swarup, 1985).
Esterase isoenzyme patterns of the white females have reliably identified H. cajani, H. graminis, H. sorghi and H. zeae (Meher et al., 1998).
Detection and InspectionTop of page The presence of cysts on the root surface is the most important characteristic used in the identification of H. cajani. Therefore, the most important stage for identification of H. cajani is after the formation of cysts. Sharma (1993) considers the identification of "pearly root" caused by the presence of white females to be useful in the diagnosis of H. cajani infestation of pigeon pea at the vegetative stage at 30-35 days after planting in infested soil.
Similarities to Other Species/ConditionsTop of page H. cajani may be confused with H. trifolii which has similar morphology and also attacks leguminous plants. Sharma and Swarup (1983) gave an identification scheme for differentiating Heterodera species occurring in India, including H. cajani. H. cajani has an underbridge of moderate length averaging 65 µm compared with those averaging 49 µm long in H. zeae and 80-100 µm long in H. trifolii and H. galeopsidis. Stylet and tail length of J2 H. cajani are 25-30 and 31-52 µm long compared with 22-27 and 56-70 µm long, respectively, in H. trifolii.
Prevention and ControlTop of page
An integrated control approach involving summer ploughing, crop rotation, seed treatment, limited applications of chemicals and the use of resistant varieties should be adopted for the control of cyst nematodes (Yadav, 1986). After cyst nematodes have infested a field, it is practically impossible to eliminate them.
Cyst nematodes are highly resistant to chemical control because the female, after death, transforms into a tough brown sac protecting the eggs which remain within.
Fensulfothion, when evaluated as a seed treatment for pigeon pea, reduced nematode populations, with high concentrations and long soaking period being the most effective (Zaki and Bhatti, 1986a). Seed soak treatments with dimethoate, acephate and quinalphos did not give effective control (Velayutham, 1988a).
Certain chemicals stimulate juvenile emergence and can be used with proper knowledge of the biology of the parasites to control them.
Experimental studies of various synthetic chemical treatments showing some control of H. cajani include the following:
Thiride gave better control than carbendazim, mancozeb and ziram on Vigna radiata in pot experiments (Mishra and Gupta, 1991);
The following non-synthetic treatments have also provided some control:
Essential oils of Mentha piperita, Ocimum sanctum, Cymbopogon martini, C. nardus, C. winterianus, C. flexuosus and O. basilicum (Gokte et al., 1993);
Root extract of Xanthium strumarium (Malik et al., 1987);
Green manures of Vigna radiata, cowpea (Vigna unguiculata), Crotalaria juncea and Sesbania bispinosa (Devi and Gupta, 1995); fenugreek (Trigonella foenum-graecum), wild methi (Senji species), berseem (Trifolium alexandrinum) and drum stick (Moringo pterygosperma) (Devi, 1997).
Powdered leaf extracts of Terminelia arjuna on pigeon pea (Singh and Singh, 1992); Argemone mexicana, Cannabis sativa, Datura metel, Nerium indicum (Mojumdar et al., 1989); and Solanum xanthocarpum (Bhatti et al., 1997);
Latex from Calotropis gigantea and Euphorbia pulcherrima, when applied as seed dressing to V. radiata (Gupta et al., 1999).
Oil cakes of neem, mustard and mahua (Rai and Singh, 1995, 1996a; Devi and Gupta, 1996).
Plant parasitic nematodes have many natural predators and parasites in the soil which provide opportunities for biological control.
Combinations of biocontrol agents and vesicular arbuscular mycorrhizal fungi have been used to manage the wilt disease complex of pigeon pea caused by H. cajani and Fusarium udum [Gibberella indica]: Bacillus subtilis, Bradyrhizobium japonicum and Glomus fasciculatum (Siddiqui and Mahmood, 1995a); Paecilomyces lilacinus, Verticillium chlamydosporium and Gigaspora margarita (Siddiqui and Mahmood, 1995b); and Trichoderma harzianum, V. chlamydosporium and Glomus mosseae (Siddiqui and Mahmood, 1996).
The use of resistant varieties is the most economical method of controlling plant parasitic nematodes. A greenhouse technique to screen pigeon pea for resistance to H. cajani is described by Sharma et al. (1991).
Several screening progammes have been carried out to identify resistance to H. cajani in the following crops:
Pigeon pea and its wild relatives Cajanus platycarpus and others (Sharma et al., 1993c; Sharma, 1995; Singh and Singh, 1995; Elyas and Sharma, 1997; Siddiqui et al., 1998a);
Vigna radiata and V. mungo (Devi and Gupta, 1987; Siddiqui et al., 1999);
Cowpea, in which generally low levels of resistance have been reported (Sharma and Sethi, 1978b; Devi and Gupta, 1991; Balasubramanian et al., 1996);
Sesame, when none of 43 genotypes showed resistance (Rana and Dalal, 1993).
H. cajani has a very restricted host range and is mostly confined to the Fabaceae. Growing the host crop in rotations every 4-5 years with non-hosts can help to maintain populations below threshold levels. The significance of double crop (intercrop and sequential crop), single crop (rainy season crop fallow) and rotations on the densities of H. cajani and other nematodes was studied by Sharma et al. (1996b). Mean population densities of H. cajani were about eight times lower in single crop systems than in double crop systems, with pigeon pea as a component intercrop. Plots planted to sorghum, safflower and chickpea in the preceding year contained fewer H. cajani eggs and juveniles than did plots previously planted to pigeon pea, cowpea or Vigna radiata. Continuous cropping of sorghum in the rainy season and safflower in the post-rainy season markedly reduced the population density of H. cajani.
Intercropping sorghum with a tolerant pigeon pea cultivar could be effective in increasing the productivity of traditional production systems in H. cajani infested regions (Sharma et al., 1996b).
ReferencesTop of page
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Distribution MapsTop of page
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