Evaluation of hybrid rice parental lines against bacterial blight disease and detection of resistant gene (s) by gene‐specific, linked markers

Abstract

AbstractBacterial blight (BB) disease, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the major bottlenecks of rice (Oryza sativa) production. The present study was undertaken to identify BB‐resistant parental lines of hybrid rice based on pathogenicity tests and molecular screening. Three virulent races of Xoo, i.e. BXo93, BXo822 and BXo887 were used to evaluate the 66 maintainers and 200 elite restorer lines against BB. Based on the pathogenicity test, none of the maintainer lines was found resistant, whereas 16 restorers were resistant against the three races and 15 restorers were resistant to a single race (Bxo93). These 31 restorer lines were selected to detect the presence of major bacterial blight resistance genes, i.e. Xa4, xa5, Xa7, xa13, Xa21 and Xa23 using molecular markers. Thirteen restorer lines carried the Xa4 gene but were not resistant to all three races of BB. Fourteen restorers and one restorer had two (Xa4 + xa5; Xa4 + Xa7; Xa4 + Xa21 and Xa7 + Xa21) and three (Xa4 + xa5 + Xa7) BB resistance genes, respectively. Genotypes having Xa21, Xa7 + Xa21 or Xa4 + Xa21 had reduced lesion lengths that ranged from 1.4 cm (against BXo93)–3.0 cm (against BXo887), 1.6 cm (against BXo93)–2.0 cm (against BXo822 and BXo887) and 2.5 cm (against BXo887)–3 cm (against BXo822), respectively, and were found to be the most effective resistance genes against bacterial blight. The restorer lines having the Xa21, Xa7 + Xa21 or Xa4 + Xa21 could be used as parental lines for the development of bacterial blight‐resistant hybrid varieties.