Dyah Anindita Asriwulan

Erwinia amylovora herbicola Atypical erwinias carotovora : Erwinia rhapontici

Facultative anaerobic bacteria Gram negative Usually single Non-spore forming Non-capsulated Rods (0,5-0,8 x 1,2-1,5 µ) Motile by several Peritrichous flagella G-C content of DNA : 51,0-53,1 % Antibiotic sensitivity : erythromycin, aureomycin, chloramphenicol, streptomycin, terramycin, tetracycline, and dimethyl chlorotetracycline Distinguish from other non-pectolytic species of Erwinia in the carotovora group : falilure to grow at 37°C, inability to produce gas from glucose, inhibition by KCN, production of acetoin, ability to reduce sucrose, and production of acid from raffinose, melezitose, dulcitol, and lactose

E. rhapontici is able to convert sucrose into isomaltulose (palatinose, 6- O-alpha-D-glucopyranosyl-D-fructose) and thehalulose (1-O-alpha-D- glucopyranosyl-D-fructose) by the activity of a sucrose isomerase. Isomaltulose (commonly referred to as palatinose, 6-O-a-D- glucopyranosyl-D-fructose) and trehalulose (1-O-a-D-glucopyranosyl- D-fructose) are functional isomers of sucrose. The adaptive role of sucrose isomer formation is unclear. Many bacteria have evolved biochemical systems for the production of storage compounds that serve as reserve material. These storage compounds become especially important under conditions of limited nutrient supply. Therefore, it was suspected that the bio-conversion of sucrose may be a method of irreversibly sequestering a carbon and energy source in a form unavailableto competitors such as the host plant or other microorganisms

The formation of sucrose isomers in E. rhapontici, a pathogen associated with crown rot in rhubarb, is accomplished through the activity of a single enzyme, which has been located to the cell’s periplasmic space (5). This sucrose isomerase is strictly substrate specific toward sucrose, with a Km of 0.28 M, whereby the reaction is essentially irreversible ). The yield of palatinose formed from sucrose is about 85%. The remaining 15% is trehalulose.

The most obvious characteristic of strains of Erwinia rhapontici The pink pigmen is soluble in water and alcohol, but not in chloroform Media which induce production of pink pigment : yeast-dextrose- calcium carbonate agar, nutrient broth yeast extract agar, sucrose- peptone agar, nutrient glycerol and potato glucose agar, King’s B medium, yeast-dextrose-chalk agar, and sucrose peptone agar, potato glucose agar, and potato dextrose agar Pink pigment of E. rhapontici was proferrorosamine A which chelates iron, converting to ferrorosamine. Proferrorosamine A is a metabolite of E. rhapontici. Proferrorosamine A cause of iron deficiency in plants, and could also be a virulence factor of E. rhapontici. 10 ppm : inhibited growth of wheat and cress seedlings. 100 ppm : strong inhibited germination of cress and wheat seeds

E. rhapontici can be isolated from water, soil, and plant surfaces. E. rhapontici is an opportunistic bacterial plant pathogen and infects its host trough wounds. The other condition conducive to infection by E. rhapontici is a prolonged period of high humidity. E. rhapontici can overwinter on infected tissues of crops in western Canada. Strain of E. rhapontici are not host-specific. Economic impact E. rhapontici can affect seed yield and seed quality. Field studies ofbpink seed of dry pea revealed that E. rhapontici reduced the size, seedling emergence and pre-elongation seedling height The seedling height was reduced by 46% compared to plants from healthy seeds.

Seed treatment : phytobacteriomycin and dithane M-45 Biological control : Pseudomonas sp. And Bacillus subtilis. The mechanism of action of antagonistic substances of B.subtilis againts Erwinia spp. Was to damage the K + ions transport of sensitive phytopathogenic bacteria via cell walls. Control of vectors : control of eelworm.