Erwinia Carotovora Var Research Articles

Attenuation by Divalent Cations of the Effect of the Phytoalexin Rishitin on Erwinia carotovora var. atroseptica

SUMMARY: Rishitin at 300 μg ml−1 rapidly decreased oxygen uptake by Erwinia carotovora var. atroseptica suspended in 0·1% (w/v) peptone water. Variation in the composition of the suspending medium affected sensitivity to rishitin, with Mg2+ and, to a lesser extent, Ca2+ decreasing bacterial sensitivity. Addition of 100 μg rishitin ml−1 affected cell membrane permeability causing an increase in conductivity of the suspending medium. Inhibition of oxygen uptake by the cationic surfactant hyamine 2389 or by sodium lauryl sulphate was also alleviated by the addition of Mg2+ suggesting that rishitin may act directly on cell membranes of bacteria, possibly in a manner similar to a cationic surfactant or a membraneactive antibiotic. The results also suggest that the sensitivity of E. atroseptica to rishitin in potato tubers may be affected by variation in their Mg2+ or Ca2+ content. Phaseollin did not inhibit respiration of E. atroseptica.

Some Properties of the False Broomrape Causal Agent and its Persistence in Soil and Refrigerated and Frozen Tumor Tissues

NIELSEN, L. W. 1978. Some properties of the false broomrape causal agent and its persistence in soil and refrigerated and frozen tumor tissues. Phytopathology 68:1068-1070. The false broomrape causal agent from ground tobacco exposed to meteorological conditions. It was recovered from root tumors suspended in a buffer solution sedimented from tumors refrigerated at approximately 6 C for I yr and tumors suspension at 48,000 g for 20 min, was retained on a 0.45 pm frozen at -20 C for 4.5 yr. The level of infection obtained on filter, was inactivated with chloroform, and was insensitive to tobacco assay plants indicated the causal agent might persist streptomycin sulfate. These responses to the treatments are more than 5 yr in a sand-soil mixture and 4.5 yr in frozen similar to those of some pathogenic bacteria. The agent tumor tissues. persisted 5 yr in an artificially infested sand-soil mixture The causal agent of false broomrape (FBR) is pestle and diluted at the ratio (w/ v) of 1 g of tissue to 4 ml unknown. It has been postulated that the hyperplastic of buffer. These, or variously treated, suspensions were growths (tumors) on tobacco roots might be caused by inoculated to roots of tobacco seedlings as described by Agrobacterium tumefaciens (Smith and Townsend) Dukes et al. (1). The inoculated seedlings were planted in Conn or Corynebacteriumfascians (Tilford) Dowson (6), a sand-soil mixture in 5-cm pots and incubated in a sand but typical tumors did not develop on tobacco roots bath at 35 C (2) for 7 days with irrigation supplied as inoculated with C. fascians (5). Nor have these or other needed. Then the soil and established tobacco plant were organisms capable of causing the tumors been isolated transferred to a 15-cm diameter pot of the sand-soil from the hyperplastic growths (6). Apparently, the FBR mixture. Each plant was fertilized weekly with 100 ml of causal agent is nonsystemic; when tumorous growths nutrient solution and grew for 2.5 to 3.5 mo in a were grafted as scions to healthy tobacco plants, tumors greenhouse maintained at 29 C minimum. At harvest, the did not develop on the stock roots (5). However, the soil was washed from the roots and they were examined disease agent can be transmitted by grinding the tumors for FBR tumors. into a slurry and inoculating the root systems of young To obtain information on some properties of the FBR plants with it (1), and the tumors are used as experimental causal agent, suspensions of it, tobacco mosaic virus inoculum. Observational evidence also indicates the (TMV), and Erwinia carotovora var. carotovora (Jones) causal agent is soilborne. The disease recurred annually in Dye were compared for sedimentation at 48,000 g for 20 a Georgia tobacco plant bed (P. D. Dukes, personal min, passage through 0.8 and 0.45 /,m filters, and communication), and developed in sweetpotato planted inactivation by chloroform (4 ml/ 5ml of suspension) and in one batch of potting soil in North Carolina (4). The streptomycin sulfate at 100 /ig/ml. Tobacco leaves agent was reported to persist in tumor tissue 15 days at infected with TMV were ground in and diluted with -20 C (7). buffer as for the FBR tumors. Both suspensions were

Quantitative Studies on the Generation of Aerosols of Erwinia carotovora var. atroseptica by Simulated Raindrop Impaction on Blackleg‐infected Potato Stems

Quantitative studies on the generation of bacterial aerosols by simulated raindrop impaction on potato stems infected with the blackleg organism Erwinia carotovora var. atrosep:ica have shown that, theoretically, airborne transmission might result in re‐contamination of blackleg‐free potato stocks.

Studies on bacterial soft rot of celery in Victoria

The causal organism of bacterial soft rot of celery was isolated and characterized, and its control was studied. The causal organism was identified as Erwinia carotovora var. carotovora (Jones) Dye. It was also pathogenic on potato in the glasshouse, causing atypical black leg symptoms. The practical implications of this finding are discussed. Infection appeared to occur at all temperatures tested in the range 1-35�C. Disease development was optimal at 30�C, but was completely checked at 1�C. Four chemicals were evaluated in the laboratory for control in transit and storage. Sodium hypochlorite provided the best control. Two copper fungicides were evaluated in the field. Cupric hydroxide provided the best control. The suitability of using this fungicide for the control of Septoria leaf spot as wall, during summer, is discussed.

The effect of rishitin on Erwinia carotovora var. atroseptica and other bacteria

Aqueous methanol extracts of potato tubers rotted in air after inoculation with Erwinia carotovora var. atroseptica ( E. atroseptica) were inhibitory to the growth of E. atroseptica in vitro. Fractionation of these extracts by column and thin-layer chromatography showed that the inhibitory activity was associated with rishitin. Pure rishitin was tested against E. atroseptica in several liquid media and caused a 50% reduction in viability at 106 μg/ml in 0·1% peptone water. A method is described for locating compounds inhibitory to E. atroseptica on thin-layer chromatograms. Using this technique rishitin was shown to be the major inhibitor in extracts of rots from eight cultivars. Other, relatively minor areas of inhibition were located on chromatograms but these inhibitors were not identified. Phytuberin and spirovetiva-1(10),11-dien-2-one did not affect the viability of E. atroseptica. Rishitin was active against five other bacteria.

Identification of the pathogen causing blackleg of potatoes in New Zealand

Abstract The pathogen responsible for blackleg of potatoes has been isolated in New Zealand for the first time and identified as Erwinia carotovora var. atroseptica (van Hall) Dye, 1969.

Infection of potato tubers with soft rot bacteria

SUMMARYStolons attached to developing potato tubers were inoculated with the soft rot bacterium Erwinia carotovora var. atroseptica.Almost all the stolons rotted, but soft rots developed in less than 10% of new tubers; the bacterium was isolated later from these tubers. No rots developed in the other tubers but the bacterium was later isolated from about half of them. It could not be isolated from tubers attached to inoculated stolons where the rot on them did not extend to the tuber or from tubers attached to stolons that were not inoculated though many of these rotted.The bacterium was reisolated from almost all arrested lesions in tubers inoculated 8 month earlier with E. carotovora var. atroseptica. Blackleg did not develop from plants grown fom these tubers under various soil conditions. It did develop in a large proportion of plants from tubers inoculated shortly before planting and grown in cool, wet soil.Less than 1% blackleg developed in plants grown from tubers from plants with blackleg or from plants immediately adjacent.The presence of pectolytic bacteria and E. caratovora var. atroseptica in seed and new tubers was investigated during June, July and August. Although E. caratovora var. atroseptica was obtained from c. 40% tubers, only c. 0·3% of c. 8400 plants developed blackleg. The bacterium was isolated from only three of 160 new tubers sampled during the summer.

The Nature of Reducing Compounds Formed from Sucrose by Erwinia carotovora var. atroseptica

SUMMARY: When grown in a medium containing 2 to 4% sucrose, Erwinia carotovora var. atroseptica formed two reducing compounds which accumulated in the culture medium. These compounds had the properties of the disaccharides 6-O-α-d-glucopyranosyl-d-fructofuranose (palatinose, isomaltulose) and 1-O -α-d-glucosyl-fructose.

Occurrence of rishitin and phytuberin in potato tubers inoculated with Erwinia carotovora var. atroseptica

The phytoalexins rishitin and phytuberin are produced in potato tubers var. King Edward inoculated with Erwinia carotovora var. atroseptica and incubated in aerobic conditions at 11 °C. Concentrations of up to 1215 μg rishitin and 165 μg phytuberin/g fresh weight of infected tissue were found. Only trace amounts (less than 0·2 μg/g fresh weight) of these compounds were found in uninoculated tissue.