APPRAISAL OF RESISTANT GENES AND GENE PYRAMID LINES OF RICE AGAINST INDIGENOUS PATHOTYPES OF Xanthomonas oryzae pv. oryzae IN PUNJAB, PAKISTAN

Abstract

The studies were carried out to identify the resistant potential of 26 IRBB lines (10 Near Isogenic Lines (NILs) and 16 pyramids) provided by the IRRI, Philippine, against 29 prevailing pathotypes of Xanthomonas oryzae pv. oryzae (Xoo) under artificial inoculation field conditions. The inoculation was done at pre-panicle emergence stage through clipping method and IR24 was used as a susceptible check. The experiment was carried out in a split plot manner during 2013 & 2014. Disease scoring was carried out 21 days after inoculation. None of the NILs or gene pyramids provided complete protection against all the pathotypes. However, Xa21 expressed resistance against 93% Xoo pathotypes followed by xa13, Xa7, Xa10 and Xa14 conferring resistance to 79, 72, 72 and 72% pathotypes respectively. Among gene pyramids, IRBB-57 (Xa4, xa5, Xa21) exhibited incompatible reaction against 93% Xoo pathotypes followed by IRBB-64 showing resistance against 86% Xoo pathotypes including pathotype-1. The rest of the Xa genes either alone or in pyramid were moderately susceptible to susceptible. Based on the current study, IRBB-21, IRBB-13, IRBB-7, IRBB-10 and IRBB-14 as a single gene and IRBB-57, IRBB-64, IRBB-53 and IRBB-54 as pyramid are recommended to mitigate the BLB severity. The temptation of newly identified Xa gene evaluation is required for achieving complete resistance against all the Xoo pathotypes. Thus, the resistant genotypes could be considered a potential source for disease resistance and could be used further in the breeding programme for development of Bacterial leaf blight resistant rice varieties.