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.
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).
Related invasive species
- Burkholderia caryophylli
Related Farm Practice
- Invasion
- Cuttings
- Soil
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).
Plants may survive about 1-2 months, but secondary invasion by fungi, such as Fusarium spp., accelerates death. Heavily infected cuttings wilt and die before roots are formed. For more information, see Dimock (1950), Hellmers (1958), Lemattre et al. (1964), Garibaldi (1967), Lemattre (1969) and Saddler (1994).
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).