Abstract
Wild introgressions play a crucial role in crop improvement by transferring important novel alleles and broadening allelic diversity of cultivated germplasm. In this study, two stable backcross alien introgression lines 166s and 14s derived from Swarn/Oryza nivara IRGC81848 were used as parents to generate populations to map quantitative trait loci (QTLs) for yield-related traits. Field evaluation of yield-related traits in F2, F3, and F4 population was carried out in normal irrigated conditions during the wet season of 2015 and dry seasons of 2016 and 2018, respectively. Plant height, tiller number, productive tiller number, total dry matter, and harvest index showed a highly significant association to single plant yield in F2, F3, and F4. In all, 21, 30, and 17 QTLs were identified in F2, F2:3, and F2:4, respectively, for yield-related traits. QTLs qPH6.1 with 12.54% phenotypic variance (PV) in F2, qPH1.1 with 13.01% PV, qTN6.1 with 10.08% PV in F2:3, and qTGW6.1 with 15.19% PV in F2:4 were identified as major effect QTLs. QTLs qSPY4.1 and qSPY6.1 were detected for grain yield in F2 and F2:3 with PV 8.5 and 6.7%, respectively. The trait enhancing alleles of QTLs qSPY4.1, qSPY6.1, qPH1.1, qTGW6.1, qTGW8.1, qGN4.1, and qTDM5.1 were from O. nivara. QTLs of the yield contributing traits were found clustered in the same chromosomal region. qTGW8.1 was identified in a 2.6 Mb region between RM3480 and RM3452 in all three generations with PV 6.1 to 9.8%. This stable and consistent qTGW8.1 allele from O. nivara can be fine mapped for identification of causal genes. From this population, lines C212, C2124, C2128, and C2143 were identified with significantly higher SPY and C2103, C2116, and C2117 had consistently higher thousand-grain weight values than both the parents and Swarna across the generations and are useful in gene discovery for target traits and further crop improvement.
Highlights
Rice is one of three major food crops across the world especially in the most populated regions, and it provides up to 23% of calories for human consumption (Fisher et al, 2000)
Alien introgression lines/Back cross introgression lines (BILs) were used as a crossing material in this study, which is a novel approach to detect QTLs and is further useful for QTL/gene pyramiding
C212, C2124, C2128, C2143, and C2162 were significantly higher yielding than Swarna and 14s and carried alleles for qTGW8.1 from O. nivara in either a homozygous or heterozygous condition
Summary
Rice is one of three major food crops across the world especially in the most populated regions, and it provides up to 23% of calories for human consumption (Fisher et al, 2000). Rice breeders have major challenges in increasing the yield potential of the cultivars as there is stagnation due to narrow genetic diversity available in cultivated germplasm. Because of the narrow genetic base of the cultivars, there is a need to transfer genes of desirable traits from wild to cultivated rice, and it is an essential strategy in pre-breeding. Several yields enhancing quantitative trait loci (QTLs) have been mapped in the last 25 years from wild species of rice for genetical improvement (Swamy and Sarla, 2008; Gaikwad et al, 2021). O. nivara accessions showed high genetic diversity in its gene pool with adaptability in different environments (Sarla et al, 2003; Juneja et al, 2006) and is a proven choice to improve the yield levels of cultivars (Vaughan et al, 2003, 2008; Swamy et al, 2014; Ma et al, 2016)
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