Evaluation of advanced breeding lines of rice for resistance to emerging pathotypes of Xanthomonas oryzae pv. oryzae in Punjab

Two hundred forty four entries from National Screening Nursery-1 (NSN-1) and six hundred forty two entries from National Screening Nursery-2 (NSN-2) were evaluated against the prevalent pathotypes viz. PbXo-7, PbXo-8 and PbXo-10 of the bacterial blight pathogen in Punjab, India under artificial inoculation conditions. Virulence/avirulence reaction of the three pathotypes to Xa/xa genes indicated that all the pathotypes were virulent on the most of bacterial blight resistant single Xa/xa genes. None of the single gene is effective against the pathotypes prevalent in Punjab. PbXo-8 was virulent to the most important genes xa13 and Xa21 and PbXo-10 was virulent on newly identified gene Xa38. Two years data revealed that 20 entries from NSN-1 and 33 entries from NSN-2 were found to be resistant to all the three pathotypes. PbXo-10 was found to be more virulent as only 2 entries viz. IET 24554 and IET 24614 were found to be resistant, and out of these two entries, IET 24614 showed susceptible reaction to the pathotype PbXo-8. Resistant entries to these pathotypes can either be released as new varieties or further utilized as donors in multiple disease resistance breeding programmes.