Vol. 4, Issue 8, Part B (2018)

Abstract
A series of bacterial leaf blight disease samples of rice were collected from different locations of Nagaon district of Assam to identify pathotype(s) of Xanthomonas oryzae pv. oryzae (Xoo) and gene (s) responsible for resistance in rice against bacterial leaf blight disease. Altogether, 6 (six) isolates were isolated through serial dilution techniques in nutrient agar medium. Isolates were then individually inoculated to set of 8 (eight) differential rice cultivars and another set of 23 near isogenic lines of rice by clipping method. Following pathogenicity pattern of the bacterial isolates on 8 (eight) differential rice cultivars, pathotype of Xanthomonas oryzae pv. oryzae has been identified as ‘pathotype Ia’. Further, based on pathogenicity pattern on 23 near isogenic lines of rice, single gene Xa4, Xa7, xa13 and Xa21 showed resistant further, the gene pyramiding Xa4 + xa5, Xa4 + xa13, Xa4 + Xa21, xa5 + xa13, xa5 + Xa21, Xa4 + xa5 + xa13, Xa4 + xa5 + Xa21, xa5 + xa13 + Xa21 and Xa4 + xa5 + xa13 + Xa21 will also confer a stable resistant to ‘pathotype Ia’. Therefore, rice variety (ies)/cultivar(s) with any one of the above mentioned gene combinations or alone will provide stable resistant against Xanthomonas oryzae pv. oryzae (pathotype Ia). The present study has identified the pathotype of Xanthomonas oryzae pv. oryzae as ‘pathotype Ia’ for first time from Assam.