The genetic law of maize leaf spacing was studied via mixed inheritance model of major genes plus polygenes in spring and summer sowing environment, taking the six generations (P1, P2, F1, B1, B2, and F2) of 2 crosses, PH4CV/Chang 7-2 (Cross I) and PH6WC/7873 (cross II) as subjects. The aim in this paper is to provide some genetic information for maize breeders. The results showed that the optimum model of leaf spacing in Cross I was E-1 with the existence of 2 pairs of major genes in spring sowing environment, and was C-0 without any major gene detected in summer sowing environment. One pair of major genes was detected in leaf spacing of cross II under both environments. The optimum model of leaf spacing in Cross II was D-4 and D-2 in spring sowing environment and in summer sowing environment, respectively. The major genes heritability of leaf spacing in Cross I was 85% in F2 generation in spring sowing environment. Therefore, it would have a high breeding efficiency for improving leaf spacing by using single cross recombination or simple backcross in Cross I in spring sowing environment. In summer sowing environment, the polygenes heritability of leaf spacing in Cross I ranged from 88 to 93% in 3 segregating generations. In summer sowing environment, the polygenes heritabilities in B1, B2, F2 generation of cross II were 87.59, 92.02 and 91.70%, respectively. Thus, the recurrent selection and early generation selection should be adopted to accumulate positive polygenes of leaf spacing of 2 crosses to improve the efficiency of plant architecture breeding in summer sowing environment.
Key words: Maize, leaf spacing, major genes plus polygenes.
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