The combination Burkholderia caryophylli was proposed without examination of the type strain of Pseudomonas caryophylli and therefore was not valid when first published. This defect can be taken to have been corrected in subsequent studies (Urakami et al., 1994; Gillis et al., 1995).
B. caryophylli is a straight or slightly curved rod with rounded ends, occurring singly or in pairs; it is aerobic, non-sporing, motile with one or several polar flagella, Gram-negative, sudanophilic, 0.35-0.95 x 1.05-3.18 µm.
In PDA culture, colonies are round, smooth and shining with regular margins: while cream-coloured at first, colonies darken with age. On nutrient agar, growth is slow and cells die rapidly; subculturing is not possible after about a week.
A record of B. caryophylli in Colombia (CABI/EPPO, 2006) published in previous editions of the Compendium was erroneous and has been removed. B. caryophylli is a quarantine pest in Colombia (Instituto Colombiano Agropecuario, 2013).
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.
B. caryophylli is an EPPO A2 quarantine pest (OEPP/EPPO, 1978), in view of the limited number of EPPO countries in which it has been reported, and the fact that it is readily carried on cuttings in international trade. However, the lack of recent publications on this organism and the disease it causes indicate that its importance is now very minor. It is also of quarantine significance for JUNAC.
Carnations are the main host. However, Dianthus barbatus and D. allwoodii can be infected through artificial inoculation. In Florida, USA, and Japan, Limonium sinuatum is also reported to be infected (Jones and Engelhard, 1984; Nishiyama et al., 1988).
Symptoms may take 2-3 years to manifest themselves, particularly when cuttings are mildly infected and maintained at relatively low temperatures. Foliage becomes greyish-green, later yellowing and wilting and then death may occur.
In stems, at soil temperatures below about 17°C, a rapid multiplication of cells leads to tension around the vessels and longitudinal, internodal stem cracks appear, usually at the base of the plant, and later develop into deep cankers. Initially, this cracking is very similar to the physiological cracking observed in certain cultivars. However, in pathogen-induced cracks, a brownish-yellow bacterial slime is visible, often overgrown with saprophytic fungi such as Mycosphaerella tassiana. In some cases, the extrusions from the cankers leave the stems hollow. At 20-25°C, cankers are more rare and wilting is the common symptom. Visual observation of peeled stems reveals sticky, brownish-yellow, narrow or broad, longitudinal stripes in the vascular tissue; in cross section, these appear as irregular brownish spots with a water-soaked margin.
Roots of infected plants, once wilting occurs, are more or less rotten, the plants being easily pulled out of the soil and, on cutting, roots show discontinuous brown spots which distinguish the disease from that caused by Phialophora cinerescens which leaves the roots apparently symptomless (EPPO/CABI, 1996a).
The bacterium can only enter plants through wounds, and subsequently colonizes the vascular system of the stem and roots. The primary infection source is infected cuttings taken from mother plants with a latent infection. Bacteria can pass from one cutting to another in the water of the propagating bed or, if the cuttings are held in water, before planting out. The observed slow, scattered spread of the disease indicates that spread occurs only from one root system to another. Bacterial slime is exposed when stems crack and this inoculum may be transferred from one plant to another. Temperatures over 20°C accelerate bacterial growth and therefore symptom expression, while at low temperatures infected plants may show no symptoms. For more information, see Dowson (1929), Burkholder (1942), Dimock (1950), Hellmers (1958), Garibaldi (1967).
The natural spread of the pathogen is very slow and over extremely short distances. The main path of distribution is by means of infected cuttings which may be obtained from infected but symptomless mother plants.
To make a reliable diagnosis, many old and young stems should be examined and isolations made from diseased tissue. Microscopic observation of stem sections shows neoformations around infected vessels, plugging of vessels, hyperlignification of their walls and necrosis. Since latent infections on cuttings cannot be readily detected, cuttings should be kept at a relatively high temperature to ensure maximum symptom expression. The bacterium can be reliably detected by immunofluorescence staining (IFAS) and direct isolation even in material with latent infection (Muratore et al., 1986). B. caryophylli has also been detected from inoculated carnation by PCR and LAMP (Loop-mediated isothermal amplification) (Kazushi et al., 2005).
To make a reliable diagnosis, many old and young stems should be examined and isolations made from diseased tissue. Microscopic observation of stem sections shows neoformations around infected vessels, plugging of vessels, hyperlignification of their walls and necrosis. Since latent infections on cuttings cannot be readily detected by direct observation, cuttings should be kept at a relatively high temperature to ensure maximum symptom expression.
Both B. caryophylli and Dickeya chrysanthemi, the slow wilt-pathogen, can be latently transmitted in cuttings taken from infected mother plants. Differences in symptom expression are evident (Bazzi et al., 1987), however in both cases early detection is desirable (Minardi et al., 1988). Both bacteria can be detected by immunofluorescence staining (IFAS) and direct isolation even in material with latent infection (Muratore et al., 1986). For more information, see EPPO/CABI (1996b, c).
The carnation strain of D. chrysanthemi (EPPO/CABI, 1996b), which causes a similar disease, is readily distinguishable in nutrient agar culture by its rapid growth of greyish-white, lobate colonies. In addition, internal symptoms of the two diseases are different.
In addition, Burkholderia andropogonis, also a pathogen of carnation, though generally considered to be foliar rather than systemic, can be detected using serological methods. Whilst this method is effective the specific monoclonal antibody developed was shown to possess cross-reactivity with B. caryophylli (Li et al., 1993).
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.
There are no direct control measures against B. caryophylli. Disease-free mother plants should be used and rooting beds and soil should be fumigated. In countries where the disease occurs, cuttings should be taken from separately grown mother plants derived from biologically tested, healthy cuttings. EPPO accordingly recommends that consignments should come from a place of production found free from B. caryophylli during the last growing season (OEPP/EPPO, 1990). However, the introduction of an EPPO-recommended certification scheme for carnation (OEPP/EPPO, 1991) provides a satisfactory alternative to such plant quarantine requirements.
Breeding of resistant cultivars is another strategy to control the disease (Onozaki et al., 1998, 1999). RAPD markers associated with genes controlling wilt resistance have been identified (Onozaki et al., 2003, 2004).
Garibaldi A, 1967. A new bacterial disease of carnation in Italy. Informatore Fitopatologico, 17:9-11.
Gillis M; Van VanT; Bardin R; Goor M; Hebbar P; Willems A; Segers P; Kersters K; Heulin T; Fernandez MP, 1995. Polyphasic taxonomy in the genus Burkholderia leading to an emended description of the genus and proposition of Burkholderia vietnamiensis sp. nov. for N-fixing isolates from rice in Vietnam. International Journal of Systematic Bacteriology, 45:274-289.
Hellmers E, 1958. Four wilt diseases of perpetual flowering carnation in Denmark. Dansk Botanisk Arkiv, 18:1-200.