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Wild species are known to be reservoir for agronomically important traits including disease resistance in crops. Bacterial blight (BB) is one of the major diseases of rice causing significant yield reduction, and host plant resistance plays a major role in the management of the disease. In this study, we employed backcross introgression lines (BILs) of 'Swarna' containing wild introgressions from two accessions of Oryza nivara IRGC81848 and IRGC81832 in order to map quantitative trait loci (QTLs) for BB resistance. A total of 22 and 43 QTLs for BB resistance were detected respectively on 12 chromosomes, which explained between 2.5% to 18.09% of the phenotypic variance in the two populations. Of the significant QTLs, qBB‐1‐1 (RM259‐RM9) and qBB‐10‐1 (RM474‐RM271) were detected across the two populations and the resistance contributing alleles were from donor wild accessions. Two major QTLs in 'Swarna'/O. nivara IRGC81848 (NPS lines) and seven QTLs in 'Swarna'/O. nivara IRGC81832 (NPK lines) were consistently detected across the years in the respective populations. Novel QTLs qBB‐10‐1 and qBB‐12‐1 are identified as candidate genomic regions for further fine mapping. These stable QTLs identified can be utilized for enhancing BB resistance in elite rice genotypes via marker‐assisted or genomic selection strategies. [ABSTRACT FROM AUTHOR]

Backcross inbred lines (BILs) derived from elite x wild crosses are very useful for basic studies and breeding. The aim of this study was to map quantitative trait loci (QTLs) associated with yield and related traits and to identify chromosomal segment substitution lines (CSSLs) from unselected BC2F8 BILs of Swarna/Oryza nivara IRGC81848. In all, 94 BILs were field evaluated in 2 years (wet seasons, 2014 and 2015) for nine traits; days to 50% flowering, days to maturity (DM), plant height (PH), number of tillers, number of productive tillers, panicle weight, yield per plant, bulk yield, and biomass. BILs were genotyped using 111 polymorphic simple sequence repeats distributed across the genome. Fifteen QTLs including 10 novel QTLs were identified using composite interval mapping, Inclusive composite interval mapping and multiple interval mapping (MIM). O. nivara alleles were trait-enhancing in 26% of QTLs. Only 3 of 15 QTLs were also reported previously in BC2F2 of the same cross. These three included the two major effect QTLs for DM and PH detected in both years with 13 and 20% phenotypic variance. Further, a set of 74 CSSLs was identified using CSSL Finder and 22 of these showed significantly higher values than Swarna for five yield traits. CSSLs, 220S for panicle weight and 10-2S with consistent high yield in both years are worthy of large scale field evaluation. The major QTLs and 22 significantly different CSSLs are a useful resource for rice improvement and dissecting yield related traits. [ABSTRACT FROM AUTHOR]