Validation Of QTGW101, A Quantitative Trait Locus For1000-Grain Weight In Rice (Oryza Sativa L.)

This study was conducted to validate a quantitative trait locus (QTL) for1000-grain weight (TGW)which was previously mapped in a3.7Mb region on the long arm of rice chromosome1, and to locatethis QTL more precisely, thus to lay a foundation for cloning of the QTL. Three BC2F8:9and twoBC2F10:11near isogenic line (NIL) sets were derived from two BC2F5plants of the indica rice crossZhenshan973/Milyang46, respectively. One plant carrying a heterozygous segment in the intervalRM11448RM11615on the long arm of rice chromosome1was detected by assying the BC2F5population with SSR markers. Three sets of BC2F8:9NILs with sequential segregating regions ofRM11448RM11522, RM11448RM11549and RM1232RM11615, respectively, and referred as C1,C2and C3, were constructed through consecutive selfings and SSR marker assays. A BC2F8plantheterozygous in the interval RM11543RM11621was obtained by assaying the selfing progenies of theother BC2F5plant. Two sets of BC2F10:11NILs segregating in the interval RM11543RM11554andRM11569RM11621, respevtively, were constructed through consecutive selfings and SSR markerassays, and were named as G1and G2. The BC2F8:9and BC2F10:11NIL sets were planted in Fuyang,Zhejiang province in paddy field in the summer of2012and2013, respectively. Heading date (HD),TGW and grain shape traits, including grain length and width, were measured in this experiment.Two-way analyses of variance (ANOVA) were performed to test the phenotypic differences betweentwo genotypic groups in each NIL set using SAS procedure. Among the BC2F8:9NILs, no significantvariations were observed on TGW and grain shape in the NIL set C1which was segregated in theinterval RM11448RM11522, whereas significant genotypic effects were detected in the remaining twoNIL sets in which the enhancing alleles were all derived from Zhenshan97. In addition, the additiveeffects were0.12g and0.14g,0.011mm and0.009mm, and0.032mm for TGW, grain width and grainlength, respectively, and the phenotypic variance explained were10.55%and8.30%,17.30%and11.73%, and23.93%for the three corresponding traits, respectively. For HD, no significant effects weredetected in the three NIL sets. Based on comparison among genomic locations of the heterogeneousregions of the BC2F8:9NIL sets, qTGW1.1was delimited to a688.8kb region flanked by RM11522andRM11554. Among the BC2F10:11NIL sets, no significant effects were detected on the four traitsmeasured in the NIL G2. On the other hand, no significant effects were detected on grain weight andHD, whereas significant variations were observed on TGW and grain length in the NIL G1which wassegregated in the interval RM11543RM11554, with the Zhenshan97allele increasing TGW and grainlength, while the additive effects were0.13g and0.018mm, and the phenotypic variance explainedwere15.19%and8.57%, respectively. Comparing the genomic locations of the heterogeneous regionsof the BC2F10:11NIL sets, qTGW1.1was delimited to the region between RM11543and RM11554.Finally, qTGW1.1was delimited to a376.9kb region between markers Wn28382and RM11554combined with the mapping result of the three sets of BC2F8:9NILs. Since no significant effects weredetected in all BC2F8:9and BC2F10:11NIL sets, we predicate that qTGW1.1is a grain weight QTL independent of HD.