Abstract
Chromosome segment substitution lines (CSSLs) are useful tools for precise mapping of quantitative trait loci (QTLs) and the evaluation of gene action and interaction in inter-specific crosses. In this study, a set of 90 back cross lines at BC2F8 generation derived from Swarna x Oryza nivara IRGC81832 was evaluated for yield traits under irrigated conditions in wet seasons of 3 consecutive years. We identified a set of 70 chromosome segment substitution lines, using genotyping data from 140 SSR markers covering 94.4% of O. nivara genome. Among these, 23 CSSLs were significantly different for 7 traits. 22 QTLs were detected for 11 traits with 6.51 to 46.77% phenotypic variation in 90 BILs. Three pleiotropic genomic regions associated with yield traits were mapped on chromosomes 1, 8 and 11. The marker interval RM206-RM144 at chromosome 11 was recurrently detected for various yield traits. Ten QTLs were identified consistently in the three consecutive years of testing. Seventeen pairs of significant epistatic QTLs (E-QTLs) were detected for days to flowering, days to maturity and plant height. Chromosome segments from O. nivara contributed trait enhancing alleles. The significantly improved lines and the stable QTLs identified in this study are valuable resource for gene discovery and yield improvement.
Highlights
Rice is one of the major crops which grow across wide range of environments and supports majority of the world population mainly located in developing countries of Asia, West Africa, Latin America and the Caribbean
Advanced back cross introgression lines derived from a cross between an elite cultivar Swarna (O. sativa) as a recurrent parent and a wild accession O. nivara IRGC81832 as a donor parent[16] were used in this study at BC2F8 to BC2F10 stage after conducting single panicle selection for consecutive generations from BC2F5 and these NPK or K lines are designated as NK 1–90
Selected five plants from each replication were evaluated for 9 yield- related traits, viz., days to 50% flowering (DFF), days to maturity (DM), plant height (PH), number of tillers per plant (NT), number of productive tillers per plant (NPT), biomass (BM), single panicle weight (PW), grain yield/plant (GY), bulk yield per square metre (BY) and two derived traits; harvest index (HI) and per day productivity (PDP)
Summary
Rice is one of the major crops which grow across wide range of environments and supports majority of the world population mainly located in developing countries of Asia, West Africa, Latin America and the Caribbean. Advanced lines were genotyped at BC2F8 and a set of 74 CSSLs were constructed with donor genome coverage of 89%20 Another population developed from a cross between Swarna and O.nivara IRGC81832, was evaluated for yield and quality related traits and QTLs were mapped at BC2F2 generation[16,21,28]. This population was advanced to BC2F8 and was phenotyped in this study for 3 consecutive wet seasons and genotyped using SSR markers to identify a set of CSSLs representing complete genome of O. nivara as overlapping segments substituting Swarna segments and to detect major QTLs for yield traits. The mapping population was tested for 3 years for identifying environment and epistatic interactions of QTLs using multiple mapping procedures to identify stable significant QTLs and to understand the genetic implications of these QTLs
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