Development of high yielding IR64 x Oryza rufipogon (Griff.) introgression lines and identification of introgressed alien chromosome segments using SSR markers

Modern rice varieties that ushered in the green revolution brought about dramatic increase in rice production worldwide but at the cost of genetic diversity at the farmers' fields. The wild species germplasm can be used for broadening the genetic base and improving productivity. Mining of alleles at productivity QTL from related wild species under simultaneous backcrossing and evaluation, accompanied by molecular marker analysis has emerged as an effective plant breeding strategy for utilization of wild species germplasm. In the present study, a limited backcross strategy was used to introgress QTL associated with yield and yield components from Oryza rufipogon (acc. IRGC 105491) to cultivated rice, O. sativa cv IR64. A set of 12 BC sub(2)F sub(6) progenies, selected from among more than 100 BC sub(2)F sub(5) progenies were evaluated for yield and yield components. For plant height, days to 50% flowering and tillers/plant, the introgression lines did not show any significant change compared to the recurrent parent IR64. For yield, 9 of the 12 introgression lines showed significantly higher yield (19-38%) than the recurrent parent IR64. Four of these lines originating from a common lineage showed higher yield due to increase in grain weight and another three also from a common lineage showed yield increase due to increase in grain number per panicle. For analyzing the introgression at molecular level all the 12 lines were analyzed for 259 polymorphic SSR markers. Of the total 259 SSR markers analyzed, only 18 (7.0%) showed introgression from O. rufipogon for chromosomes 1, 2, 3, 5, 6 and 11. Graphical genotypes have been prepared for each line and association between the introgression regions and the traits that increased yield is reported. Based on marker trait association it appears that some of the QTL are stable across the environments and genetic backgrounds and can be exploited universally.