Studies On The Major Gene Plus Poly-gene Inheritance Of Seedcoat Colour In Yellow-seeded Rape (Brassica Napus L.)

Yellow-seeded rape has higher oil and protein content, lower crude fiber and polyphenol content, good oil quality and higher protein digestion and easier way to examine seed ripeness compared with dark-seeded rape under the same genetic background. For the mang merits, yellow-seeded rape breeding is considered as a very important approach to improve Brassica napus quality by many oil breeders all over the world. But the inheritance of seedcoat color in Brassica napus is apparently different from ones in Brassica campestris and in Brassica juncea. Some researchers had made many studies about the inheritance of seedcoat color in Brassica napus, but they considered seedcoat color in Brassica napus mainly as either qualitative or quantitative traits when they studied. In fact, as yellow-seeded Brassica napus L. may be obtained from different breeding approaches, its seedcoat color has showed distinctive characteristics, which has not only showed the inheritance characteristics of qualitative traits but also the ones of quantitative traits, and belongs to the qualitative-quantitative traits and should be analysed by major gene-polygene mixed inheritance model.This paper made a systemic study about the inheritance of seedcoat color and seed husk content in yellow-seeded rape {Brassica napus L.) by applying the major gene plus poly-gene model of genetic system of quantitative traits through a joint segregation analysis of P1,F1,P2,B1,B2 and F2 generations of the crosses of both GH06 (yellow-seeded self-crossing line) x 94005 (black-seeded self-crossing line) and GH06 x A800 (black-seeded self-crossing line). At the same time, the correlations among some traits were also studied in the backcross generations and F2 generations of both the crosses in this paper. The conclusions in this paper were mainly as follows:1 .The seed-colour coefficient (T2/T1) that obtained from the exposure time of seedcoat measured by dissection microscope could distinguish from seeds with different seedcoat color. The lower the seed-colour coefficient was, the yellower the seedcoat colour. It was an effective way to show the difference of the seedcoat color quickly and truly through calculating the seed-colour coefficient of seeds with different colour from the results and analyses in this paper, and also overcome the influence of subjective factors when estimating the seedcoat color in the past.2.The results indicated that the seedcoat colour in yellow-seeded Brassica napus L. belonged to qualitative-quantitative trait whose inheritance was the mixed inheritance of one major gene plus poly-gene, that poly-gene effects and environments had a strong modified function to the seedcoat color by applying the major gene plus poly-gene model of genetic system of quantitative traits through a joint segregation analysis of P1, F1,P2,B1,B2 and F2 generations of both the crosses. The interaction mode of major genes between the yellow-seeded line (GH06) and two black-seeded lines (94005 and A800) may belong to the inheritance mode of existing the different poly allele genes in the same locus. If the three different poly allele genes of the major gene wore Sc1, Sc2 and Sc3 respectively and the relation on their effect values was Sc1> Sc2> Sc3, the poly allele genotype of the major gene in yellow-seeded GH06 was Sc2Sc2 and that in black-seeded 94005 was Sc1Sc1 and that in black-seeded A800 was Sc3Sc3. As the effect of Sc1 was dominant to Sc2, the poly allele genotype Sc'Sc2 behaved with black seed . As the effect of Sc2 was dominant to Sc3, the poly allele genotype Sc2Sc3 behaved with yellow seed. In the mixed inheritance model of one major gene with negative completely dominance plus polygenes with additive and dominance in GH06x94005, the additive and dominance effects of the polygenes had a great influence on seedcoat colour. In the cross of GH06x94005, the major gene heritability of B1 was higher than the one of B2 and F2, and however the poly-gene heritability of B2 and F2 was higher than the one of B,. The heritability of seedcoat color...