Genetic analysis of leaf expansion trait in Brassica rapa L. ssp. chinensis (L.) Hanelt

Brassica rapa L. ssp. chinensis (L.) Hanelt is an important vegetable in eastern Asia. Its leaf area is one of main factor of influencing on the yield of individual plant. To reveal the mechanism of the leaf expansion, the joint segregation analysis of multiple generations (P
₁
, P
₂
, F
₁
, B
₁
, B
₂
and F
₂
) was used to analyze the genetics of leaf expansion trait in combination SW-13×L-118 of Brassica rapa L. ssp. chinensis (L.) Hanelt. In this paper, the results showed that the leaf expansion trait was controlled by one pair of additive-dominant major genes plus additive-dominant-epistatic polygene (D model). The additive effect of the major gene was -2.3061, the dominant effect was -1.4525. The heritability of major gene of leaf expansion was 2.56% in B
₁
generation, 1.55% in B
₂
generation and 12.12% in F
₂
generation. The heritabilites of the polygene were 54.04% in B
₁
generation, 25.11% in B
₂
generation, and 62.60% in F
₂
generation, respectively. It appeared that the polygene effects should be given prior to the improvement of leaf expansion trait of combination SW-13×L-118, and the selection was effective in later generation, and the negative additive effect and negative dominant effect of major gene were noticed.