Genotypic and phenotypic dissection of Xanthomonas oryzae pv. oryzae on Indica rice cultivars for bacterial blight resistance

Aim: To evaluate the level of virulence of different Xoo isolates/pathotypes of Eastern and North-eastern India and to identify the suitable donors in rice cultivars having various R-gene combination against virulent Xoo races of Bacterial Blight disease of rice. Methodology: Thirty six Xoo isolates were collected from different places of Eastern and North-eastern India and genetic diversity/similarity was examined by genotyping of pathotypes using JEL1/JEL2 markers. The 34 Indica rice cultivars carrying different R-gene combination were selected and grown in net house and inoculated artificially with Xoo inoculants from these races/isolates bacterial of blight disease. Results: The selected 36 Xoo isolates of Eastern and North-eastern India were grouped into seven different isolates/races based on their genetic diversity using JEL1/JEL2 markers. Among 34 Indica rice cultivars, three or more R-gene combination (xa5 + xa13 + Xa21 and/or Xa4 + xa5 + xa13 + Xa21) cultivars exhibited highly resistant as compared to cultivars with single and double gene combination cultivars against most of the Xoo isolates/races. Interpretation: The cultivars may determine different level of resistance due to complementary effect of inheritance of suitable R-gene combination. Identified donors may be used for rice resistance breeding programme for Eastern and North-eastern India.