identification of causal agent of bacterial bight of rice in the fields of guilan province

abstract bacterial blight of rice, causes by xanthomonas oryzae pv. oryzae , is one of the most devastating disease of rice after blast disease. during the spring and summer of 2005-2006 different paddy fields in guilan province (roodsar, langrud, lahijan, rasht, anzali, fooman, soomeesara and roodbar) were surveyed and samples were collected from rices showing blight and yellowing in leaves. the extract from tissues were cultured on na and ydc media containing cyclohexamide (50 µg/ml). after 48 to 72 hours, bacterial colonies were selected and purified. bacterial colonies were yellow mucoid and produced xanthomonadin pigment on ydc medium. strains were gram, pectinase and oxidase negative, aerobic and abel to do hypersensitivity reaction on tobacco leaves. according to morphological, physiological and biochemical characteristics, pathogenicity test, antibiotic sensitivity and pcr method with specific primer pair the isolates were identified as xanthomonas oryzae pv. oryzae. this is the first report of existence of x. o. pv. oryzae on paddy fields in the guilan provinc