| Grain shape has a direct relationship with rice production.Grain shape,which is measured by grain length,width and thickness,is a quantitative trait in genetics.So far,many grain shape genes including qGL3,GS3,GW2,GS5,GW8,GW5 and TGW6 have been mapped or cloned.Grain genes could increase yield and quality of rice by the modified grain traits,which is the ultimate goal of rice molecular breeding.In previous studies,we have genotyped and analyzed genetic effects of qGL3,GS3,GW2,GS5 and GW8 genes using a recombinant inbred line(RIL)population.In this study,we sequenced and then compared TGW6 sequences between the two parentas of TD70 and Kasalath;we analyzed the genetic effects of GW5 and TGW6 using their gene markers in RIL population;furthermore,we evaluated the genetic effects of qGL3,GS3,GW2,GS5 and GW8 in a F2 segregating population derived from the cross between a RIL G4179 and Kasalath.The main results are as follows:1.TGW6 sequences had seven single base differences between TD70 and Kasalath.The CAPs marker according to one point difference was used to classify the RIL population.140 lines with TGW6-TT(TT means two alleles were from TD70)and 100 lines with TGW6-KK(KK means two alleles were from Kasalath)were genotyped,but there were no significant difference between both genotypes.2.N1212 Indel marker was used to detect GW5 genotype.In 240 lines,98 lines had GW5-TT,while 142 lines had GW5-KK.The GW5-TT genotype showed larger shape in grain width,grain thickness and 1000-grain weight;however grain length did not show significant difference.3.Other markers of grain size genes developed previously were used to detect genotypes in F2 population.qGL3-TT,GS3-TT,GW2-TT,GS5-TT and GW8-TT genotypes were 125?156?134?150 and 200 lines,respectively.Theoretically,there should be 35=243 genotypes,but only 165 genotypes were detected.Except for GW8,other four genes were consistent with the theoretical ratio of 1:2:1.4.Genetic effect analysis of single gene showed:(1)qGL3-TT,qGL3-TK(TK means two alleles were from TD70 and Kasalath respectively),GS3-TT and GS3-TK genotypes had 1,90mm?0.72mm?1.53mm and 0.55mm in grain length,and their 1000-grain weight were 11.70g?6.53g?10.22g and 5.12g,respectively.In addition,qGL3 and GS3 could also increase grain width and grain thickness.(2)Compared to the Kasalath genotype,grain width of GW2-TT?GW2-TK?GS5-TT?GS5-TK?GW8-TT and GW8-TK increased by 0.50mm?0.18mm?0.32mm?0.13mm?0.07mm and 0.06mm,and 1000-grain weight increased by 6.93g?2.39g?1.98g?1.43g?0.68g and 0.48g,respectively.(3)According to homozygous and heterozygous genotypes,genetic effects of five grain size genes on 1000-grain weight were:qGL3>GS3>GW2>GS5>GW8.(4)GS5 and GW8 had no significant differences between homozygous and heterozygous genotypes.(5)In some grain shapes,the genetic effects from heterozygous genotype was higher than that from homozygous genotype.5.The greatest effect on grain length was derived from the combination genotype qGL3-TT+GS3-TT.The greatest effect on grain width was derived from the combination genotype GW2-TT+GS5-TT.The greatest effect on grain thicknessgenotype was derived from the combination genotype GS3-TT+GW2-TT.The greatest effect on 1000-grain weight genotype was derived from the combination genotypeGS3-TT+GW2-TT.Grain size gene waspartially dominant and the heterozygous effects.of most of grain shape genes showed middle type between two parents.Only in the combination genotype GS5+GW8,heterozygous effect showed similar with homozygous effect. |
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