Quantitative trait loci (QTL) controlling six milling and appearance quality traits were analyzed over 2 years using recombinant inbred lines derived from two indica rice Teqing and IRBB. A total of 30 QTL for these traits were detected, of which eight were for brown rice rate (BRR), two for milled rice recovery (MRR), two for head rice recovery (HRR), seven for grain length (GL), five for grain width (GW), and six for length/width ratio (LWR). The QTL were distributed on all chromosomes except for chromosomes 4 and 12. A QTL cluster with major effects on GL, LWR, BRR, and HRR was located in the RM15139-RM15303 interval on chromosome 3, which includes the GS3 gene for grain size. The phenotypic variances explained by the QTL were 59.51%, 36.68%, 19.51%, and 4.56%, respectively. QTL affecting GW, LWR, BRR, and MRR were clustered in the RM437-RM18038 region of chromosome 5,which covers the GW5 gene for grain width, and contributed 59.51%, 36.68%, 19.51%, and 4.56% to the total variance. QTL with minor effects on BRR and MRR were mapped to the RM190-RM587 interval covering the Wx gene for amylase content on chromosome 6. These results suggest that GS3 and GW5 may play a major roles in the genetic control of BRR and grain shape.
Chalkiness and grain shape are two important appearance traits of milled rice (Oryza sativa L.), and grain shape is generally considered to greatly affect chalkiness of endosperm. This study was conducted to validate and fine map an important multifunction region located on the long arm of rice chromosome 10, qPCG10/qDC10, conferring grain shape and chalkiness that has not been well characterized. The quantitative trait loci validations were first performed using BC2F2 and BC2F2:3 populations derived from indica maternal line Teqing and recurrent paternal line IR24. Plants with overlapping heterozygous segments in the interval of RM3773 to RM6673 were selected from the BC4F2 population to develop near‐isogenic lines for fine mapping of qPCG10/qDC10. Using two‐way ANOVA of phenotypic variance among three genotype groups in each near‐isogenic line set, qPCG10/qDC10 was delimited to a 93.4‐kb region flanked by RM25828 and RM3123 and showed significant effects on grain width, grain length, 1000‐grain weight, percentage of chalky grain, and degree of chalkiness. We speculated that the multifunction region may harbor a novel gene causing chalkiness and grain shape. The present study will facilitate the cloning of qPCG10/qDC10 and the exploration of the molecular mechanisms underlying rice grain chalkiness.
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