Identification of bacterial pathogens of corn in Hamedan, Khorassan Razavi , Ardabil, Khosestan, Kermansha and Semnan provinces

In this study, the major corn growing areas of Hamedan, Khorassan Razavi , Ardabil, Khosestan, Kermansha and Semnan provinces were surveyed for bacterial diseases, weekly. In early growing season, samples were taken from diseased plants showing symptoms such as water soaking of sheath, necrotic strips on the leaves or yellowing. Moreover, in mid growing season, samples from plants having soft brown nodes that in sever cases broke the stems, were taken. To isolate bacteria from these samples they were first washed with normal water and then twice with distilled water. Using a sterile scalpel some pieces from the samples encompassing the infected and healthy tissues were taken. The pieces were put in the tubes containing sterile distilled water. After 15-20 minutes using a sterile loop, suspensions of the samples were cultured by streaking the loop on NA and EMB media in Petri dishes. The cultures were then incubated at 28ΊC. After 48-72 h green metallic colonies were formed on EMB medium. To purify the cultures, the colonies were sub-cultured on the same medium. By this way 28 purified bacterial isolates were obtained. The characteristics of the isolates were as follows: They formed green metallic colonies on EMB medium, all isolates were gram negative, bacilli form, mobile with perithrichus felagella, oxidase and catalase positive. They were anaerobic, soft rot positive, used peptone, thiosulphate sodium and sistein and produced H2S. All isolates produced acid from lithmus milk, glucose, fructose, galactose, cellobiose, lactose, melibiose, sucrose, ribose, manitol, manose, ramnose, arabinose, xylose and trehalose. All isolates could also grow in 5% oral salt at 36ΊC. According to the results of the tests and the phenotypic characteristics of the isolates, two genera namely Pectobacterium chrysanthemi and Dickeya chrysanthemi comb, nov (Pectobacterium chrysanthemi) were identified. And some Strains were gram negative and produced fluorescent pigment on king B medium and were positive in levan production ,but negative in oxidase, argenine dihydrolase and potato soft rot but produced hypersensitive reaction on tobacco were identifid as Pseudomonas genius.They utilized lactose,sorbitol,sucrose,glucose,galactose and produced acid from them and probabley were belonged to Pseudomonas syringae. These strains were reported as blast and has clarified that have heterogen population in the Khorassan Razavi province.The percent of infection of these pathogens are not remarkable in the field of corn.