High-density Genetic Linkage Map Construction And QTL Mapping Of Seed Coat Color In Sesame(Sesamum Indicum L.)

Sesame（Sesamum indicum L.） is an important and one of the oldest oilseed crops. The usages of sesame according to the seed coat colors are not identical. Understanding the molecular basis of sesame testa color formation would provide helpful information for the cultivation of sesame with special color. In this study, F7 RIL population containing 548 lines was established from the white seeded Zhongzhi13（♀） and black seeded ZZM2748（♂）. Based on the RIL population, construction of genetic linkage map and QTL localization of the testa color trait were performed.The genetic linkage map was built using Joinmap 3.0 with 451 polymorphic SSR screened with parents DNA. 437 loci were mapped onto 14 linkage groups covering a total distance of 2136.58 cM with an average distance of 4.89 cM between adjacent markers.Identification of testa color through the straightforward method and colorimeter method. Straightforward method divided seeds into six color categories namely white, yellow, brown, brown, gray and black in percentages of 24%, 14%, 7%, 20%, 17%, 18% respectively; Colorimeter method test results included L, a and b, three identification index values. The minimum values of the three parameters were obtained in the black seed coat color, respectively 29.17, 2.08 and 6.62; The maximum value of the measured value L was obtained in black seed coat, 56.01; the maximum measured values about a and b were obtained in the yellow seed coat color, respectively, 7.06 and 23.00.The QTL locations for testa color associated traits in sesame were excavated with WinQTLcart2.5 and QTLnetwork2.2. We analyzed the phenotype data from two environments with WinQTLCart2.5 and obtained in total 47 QTL including 23 QTL in Hainan and 24 QTL in Hubei whereas 16 QTLs were detected repeatedly in the two experimental areas. From simultaneous analysis of genetic effects and environmental effects with QTLnetwork2.2, 16 QTL were obtained. 20 overlap QTLs located in two markers interval（< 1.5 cM） were detected in the different environments independently of the software used wherein the contribution rate is higher than 10% of the nine, namely qC1-L3（25%）, qC1-b2（12%）, qC1-L4（36%）, qC1-b3（16%）, qC1-a3（ 14%）, qC1-L5（19%）, qC5-b1（39%）, qC5-a1（14%）, qC5-L1（14%）.Through the comparative analysis between the whole genome sequence of sesame and three marker intervals harboring major QTL（ZMM2913-ZMM2239, ZMM1682-ZMM1683 and ZMM1683-ZMM1687）, 217 genes were found in the Sinbase and 130 genes were functional annotated. Three genes（SIN₁012054, SIN₁016754 and SIN₁022712） are homologous to Arabidopsis genes involved in flavonoid synthesis and 2 genes（SIN₁022697 and SIN₁022767） were reported to be related to phenylpropanes metabolism.