MARKER-ASSISTED SELECTION: EVALUATION OF BACTERIAL BLIGHT RESISTANCE IN THE PYRAMIDS OF FERTILITY RESTORER LINES

Abstract

PRR78 and KMR3 are popular restorer lines of the rice (Oryza sativa L.) hybrids Pusa RH10 and KRH2, respectively. These lines are highly susceptible to bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae. Nine families each of PRR78 and KMR3 pyramids containing Xa4, xa5, xa13 and Xa21 resistance genes were evaluated for agronomic and related characters (viz., days to 50% flowering, plant height, number of tillers, panicle length, filled grains per panicle, percentage of spikelet fertility, 1000 grain weight, yield, biomass, harvest index and disease resistance). There were no significant differences within the families of the pyramids with respect to any of the characters evaluated. Under disease-free conditions, there was no difference between the parents and the pyramid families for the characters evaluated. However, under inoculated conditions of heavy disease pressure: (i) the parents exhibited highly susceptible reaction, whereas all the families of pyramids of both genotypes were highly resistant; (ii) pronounced variation was observed between the parents and the pyramids under inoculated conditions for the characters viz., FG/P, SF %, 1000 GW and Y. With respect to yield under diseased conditions there was a loss to the extent of 28% in PRR78 and 24% in KMR3 compared to the pyramid families. The pyramids thus protected against the yield loss and pyramiding of the four resistance genes did not have any yield penalty. These pyramids can be used directly in the breeding programs or as potential donors of bacterial blight resistance.