Analysis of genetic characteristics of thousand-grain weight and grain shape in RILs population of Tartary buckwheat

<bold>Objective</bold> Thousand grain weight is one of the three major components of yield traits in Tartary buckwheat，which is determined by grain size（grain length，grain width and grain thickness）and grain plumpness.Studying genetic variation and molecular mechanism of grain weight and grain size is of great significance for Tartary buckwheat breeding. <bold>Method</bold> In the study，grain length（GL），grain width（GW），length to width ratio（L/W）and 1000-grain weight（TGW）of ‘Jinqiaomai 2 × Pinku 1’ recombinant inbred lines（JP-RILs）population were subjected to variation analysis，mixed major genes+polygene genetic model analysis，correlation analysis and cluster analysis under two environments. <bold>Result</bold> A continuous distribution and transgressive segregative distribution was observed for the four tested traits in the JP-RILs population under two environments.The coefficient of variation was the largest for L/W（15.30%，15.70%），followed by GL（11.27%，11.03%），and was the smallest for GW（5.46%，5.94%）.The optimal genetic model of GW was both MX1-A-AI under two environments，which was controlled by one additive epistatic major gene，with the heritability of the major gene of 69.84% and 62.68%，and that of the polygene of 23.90% and 34.24%.The optimal genetic model of L/W was both 4MG-AI under two environments，which was controlled by four additive major genes，with the heritability of the major gene of 98.07% and 98.26%.The optimal genetic model of GL was 4MG-AI under E₁ and 1MG-A under E₂ environment，which was controlled by four additive major genes and one additive major gene with the heritability of the major gene of 97.98% and 88.39%，respectively.The optimal genetic model of TGW was 2MG-DE under E₁ and 4MG-EEEA under E₂ environment，which was controlled by two duplicate major genes and four partly additive major genes with the heritability of the major gene of 36.61% and 70.43%，respectively.Lines with high TGW and long-tapered grains or round-shaped grains and lines with low TGW and round-shaped grains were screened by cluster analysis，which can be considered as breeding materials for new varieties and also provide good materials for genetic research. <bold>Conclusion</bold> Grain size and TGW were controlled by major genes，and the epistasis effects of major genes was highly predominant，which laid a basic foundation for QTL mapping and genetic improvement for grain size and TGW in Tartary buckwheat.