Abstract
BackgroundHigh grain yield is one of the most important traits requiring improvement in rice breeding programs. Consequently, the genetic basis of spikelets per panicle (SPP) and grain weight (TGW) have received much research focus because of their importance in rice yield.ResultsIn this study, IL28, which is a near isogenic line (NIL) developed by introgressing chromosomal segments of the cultivar ‘Moroberekan’ into the cultivar ‘Ilpumbyeo’, showed a significant increase in the number of spikelets per panicle (SPP) and 1,000-grain weight (TGW) compared to the recurrent parent, Ilpumbyeo. Quantitative trait locus (QTL) analysis in 243 F2 plants derived from a cross between IL28 and Ilpumbyeo indicated that both qSPP6 and qTGW6 are located in the interval RM3430–RM20580. Following substitution mapping with 50 F3:4:5 lines, qSPP6 was mapped to a 429-kb interval between RM20521 and InDel-1, while qTGW6 was mapped to a 37.85-kb interval between InDel-1 and SNP--3 based on the japonica genome sequence. This result indicates that qSPP6 and qTGW6 are different genes. Yield trials with substitution lines indicated that lines harboring the homozygous Moroberekan segment at both the qSPP6 and qTGW6 region showed significantly higher grain yield than Ilpumbyeo.ConclusionBecause the Moroberekan alleles for SPP and TGW have been shown to be beneficial in the genetic background of Ilpumbyeo, both the qSPP6 and qTGW6 alleles might prove valuable in improving rice yields. Closely linked SSR markers are expected to facilitate the cloning of genes that underlie these QTLs, as well as with marker-assisted selection for variation in SPP and TGW in rice breeding programs.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-014-0014-5) contains supplementary material, which is available to authorized users.
Highlights
High grain yield is one of the most important traits requiring improvement in rice breeding programs
The results indicated that there were highly significant differences (P < 0.01) in panicle length (PL), secondary branch number (SBN), spikelets per panicle (SPP), first node width (FNW), second node width (SNW), and 1,000-grain weight between IL28 and Ilpumbyeo, while no significant difference was obtained for tiller number (TN) and culm length (CL)
An increase in grain weight in IL28 which is associated with higher grain milk-filling rate might be due to the Moroberekan segment on chromosome 6 considering that no Quantitative trait locus (QTL) for grain width and weight was detected in the Moreberekan segment on chromosome 4
Summary
High grain yield is one of the most important traits requiring improvement in rice breeding programs. The genetic basis of spikelets per panicle (SPP) and grain weight (TGW) have received much research focus because of their importance in rice yield. The anticipated rapid increase in the global human population, which is expected to reach 9.1 billion by 2050, might generate serious food shortage problems. Various factors, such as water scarcity, soil salinity, disease, climate change, and reduced arable land, will exacerbate food shortages in the 50 years (Khush 1999 and Khush 2005; Zhang 2007). Researchers are focusing on increasing existing crop grain yield levels. The genetic analysis of these three yield components is difficult, because these traits are controlled
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