Improvement of resistance to bacterial blight through marker assisted backcross breeding and field validation in rice (Oryza sativa)
Bacterial blight is one of the major constraints in rice cultivation. Breeding for durable resistance is most effective and economical method to combat disease. In present study, four resistance genes (Xa4, xa5, xa13 and Xa21) were pyramided into popular cv. Mahsuri and two hybrid rice parental lines, PRR78 and KMR3 using marker assisted back cross breeding. Nine pyramid families of each background were evaluated under both artificial and natural disease conditions. Pyramids were inoculated with sixteen Xanthomonas oryzae pv. oryzae isolates collected from different parts of India. BF16 was highly virulent on recurrent parents with a yield loss of 23% in Mahsuri, 28% in PRR78 and 24% in KMR3. BF7 (10% loss in Mahsuri and 13% in KMR3) and BF10 (22% in PRR78) were least virulent. Under natural condition at Maruteru, disease showed a yield loss of 22% in Mahsuri, 28% in PRR78 and 26% in KMR3. Under both conditions, none of the pyramids were susceptible. There were no significant differences within pyramids with respect to any character evaluated. No pyramid was susceptible. The agronomic characters showed no significant difference between parent and pyramid. Yield and its related characters were statistically significant between parents and pyramids (P< 0.05). The pyramids insulated a heavy yield loss to the tune of ~28% and pyramiding of resistance genes (two dominant and two recessive) did not show any negative effect on agronomic performance of any pyramid. These pyramids can be used directly and also as valuable source of resistance in future breeding programs.
Lalitha D. Guvvala, Pranitha Koradi, Vinay Shenoy and Lalitha S. Marella