No abstract

With 5 figures and 2 tables Abstract Seed storability is an important agronomic trait for rice. A population comprising 182 backcross recombinant inbred lines derived from the backcross ‘Koshihikari’ (japonica)/‘Kasalath’ (indica)//‘Koshihikari’ was used for detecting quantitative trait loci (QTL) for seed storability. Germination rate was used as the phenotype of seed storability under room temperature conditions after storage for 32 months (grown only at Nanjing) and 48 months (grown at Nanjing, Jinhu and Lianyungang). Six QTL named qSS‐2, qSS‐3, qSS‐4, qSS‐6, qSS‐9 and qSS‐11 were detected. qSS‐9 was the most stable one and was detected in seeds from all environments and storage times, explaining 10.63–33.10% of the phenotypic variation. The existence of QTL qSS‐2, qSS‐4, qSS‐6 and qSS‐9 was confirmed using ‘Kasalath’ chromosome segment substitution lines in a ‘Koshihikari’ genetic background. These results provide an opportunity for map‐based cloning of qSS‐9, thereby gaining an understanding of seed storability in rice and possibilities for its improvement.

Seed storability in rice (Oryza sativa L.) is an important agronomic trait. Two segregating populations with N22 (indica) as a common parent, viz. a set of 122 backcross-inbred lines (BILs) derived from the backcross Nanjing35 (japonica)/N22//Nanjing35 and another population comprising 189 recombinant inbred lines (RILs) from the cross of USSR5 (japonica) and N22, were studied to detect quantitative trait loci (QTL) controlling seed storability. Germination percentage (GP) was used to evaluate seed storability after aging treated under three different conditions, viz. natural, artificial and combined aging treatments. A total of seven QTLs were identified on chromosomes 1, 2, 5, 6 and 9. Among them, a major QTL, qSSn-9, was common in the two populations. In contrast, four QTLs (qSSnj-2-1, qSSn-2-2, qSSn-5 and qSSn-6) were detected in BILs and the QTL qSSn-1 was identified in RILs, which was a new QTL for seed storability. The N22-derived alleles increased the seed storability at all the loci except qSSnj-2-1. We also investigated the effect of QTLs using five selected lines with high storability from BILs and verified qSSn-5 with a near-isogenic line (NIL). These results provide an opportunity for pyramiding or map-based cloning major QTLs for seed storability in rice.

A new QTL for spikelets per panicle (SPP) was detected on the long arm of chromosome 7 in an F 2 population derived from a cross between the japonica cultivar Hwaseongbyeo and WH29001. WH29001, an advanced backcross line was developed by introgressing chromosomal segments from an accession of O. minuta (2n = 48, BBCC, Acc. no. 101141) into the O. sativa subsp. japonica cv. Hwaseongbyeo. The O. minuta allele increased SPP in the Hwaseongbyeo background despite the fact that O. minuta was the small panicle parent. Using F 3 and F 4 progenies, spp7 was validated and mapped to a 2.3 Mb region in the interval between the SSR markers RM445 and RM21615 based on the japonica genome sequence. A yield trial using F 4 lines indicated that the lines carrying an O. minuta chromosome segment across the entire spp7 target region out-yielded its sister lines containing Hwaseongbyeo chromosome in the target region and Hwaseongbyeo by 14.3% and 15.9%, respectively. Increase in SPP in WH29001 was mainly because of the increase in primary branches per panicle. The locus, spp7 is of particular interest because of its independence from undesirable height and flowering time. SSR markers tightly linked to the spp7 will facilitate cloning of the gene underlying this QTL as well as marker-assisted selection for variation in SPP in an applied breeding program.

No abstract