Genetic Analysis And Mapping Of Seed Coat Color In Brassica Juncea

In the same genetic background,because yellow seed coats are significantly thinner than brown or black ones,the oil content of yellow seeded varieties is higher than brown or black ones,and the seed meal from yellow seeded varieties contains higher protein and lower fiber content,which improves the meal quality for poultry and livestock.Brassica napus is now the most widely cultivated oilseed species in the crucifer family.However,no yellow-seeded forms have been discovered in natural germplasm of B.napus.Most of artificially synthesized yellow-seeded B.napus varieties are affected by environment,so they are not stable enough in phenotypes. Because the genetic mechanism of seed coat color is not known,it is difficult to develop the homogeneous yellow-seeded B.napus varieties.Majority of the B.juncea accessions in China are yellow-seeded,so they are good donors for breeding pure and heritable yellow-seeded B.napusIn this study,Plant materials consist of a true breeding yellow-seeded B.juncea variety Sichuan Yellow(SY),a true-breeding brown-seeded B.juncea variety Purpleleaf Mustard(PM),four segregating mapping populations(A-BC₆F₂,A-BC₇F₁,B-BC₆F₂ and A-BC₆F₂) and other 22 genotypes(20 B.juncea and 2 B.rapa).Using SSR,SRAP,RAPD and SCAR markers we have mapped the genes for the seed coat color in B.juncea and done association mapping.The results were as follows:1.Seed coats were stained by vanilin to phenotype the seed color before maturation of seeds,and then seeds from open-pollination of the field-grown plants were scored by visual observation for seed coat color and classified into two groups: yellow or brown seeds.Through X² testing,data indicated that the color of each population was controlled by a single locus.The complementary test of NILA and NILB show that their color were controlled by different loci BjA and BjB.2.Using 500 RAPD 10-mer random primers,270 SRAP primer pairs,175 SSR primer pairs and 4 SCAR primer pairs screen polymorphic markers in both parents and their derived NILA and NILB lines.After investigating these polymorphic markers in the segregating populations,11 markers(SCAR1078,SZ1-331,SCAR57,CB10428,SCM-08,OL12-F02,Ra2-A11,Na10-A08,Me10-Em4,CB10029 and Ni4-C09) were linked with one seed coat color locus BjA,and 6 markers(CB10298, Ni4-H06,Ni4-D12,Ni3-G05,S1096_-700 and Ni4-F11) were linked with the other seed coat color locus BjB.The closest markers linked with seed coat color loci BjA and BjB,respectively,were OL12-F02,Ra2-A11,Na10-A08,Me10-Em4 and Ni4-C09, S1096_-700 and CB10298,and their genetic distances were 0.4 cM and 1.3 cM,4.0cM and 0.8 cM.3.Through comparing the map with the N9 linkage group of B.napus(Piquemal et al.2005) and the J9 and J18 linkage groups of B.juncea(Ramchiary et al.2007),it is known that there were some colinearity between the genome A of B.napus and that of B.juncea.It is also found that the marker CB10298 was transferred from the J9 linkage group of A genome to the J18 linkage group of B genome,so there might be some homeologous segments between the linkage groups J09 and J18 in B.juncea. From the information of the marker Ni3-G05,it can be speculated that TT8 be one of candidate genes for the locus BjB.4 The association mapping of 22 B.juncea and 2 B.rapa accessions indicated that the markers Me10-Em4,Na10-A08,Ra2-A11 and OL12-F02 was tightly linked with the locus BjA and CB10298 was closely linked with the locus BjB.So those linked markers will be useful for the transfer of the yellow genes into elite rapeseed cultivars using MAS.