Studies on self- and cross-imcompatibility in the artificial autotetraploids of Brassica pekinensis

I. Results of the primary and the secondary crosses based on the four different strains with perfectly homozygous genotype for oppositional genes

Abstract

Relations between the behaviour or the function of the oppositional genes and the fertility in the artificial autotetraploids of Chinese cabbage (Brassica pekinensis Rupr.) were studied. In a diploid variety “Kanazawa-Hakusai”. four homozygous strains, S₁S₁, S₂S₂, S₃S₃ and S₄S₄, were analysed by the crossing experiments, and their correspondent autotetraploids were induced. The results of the selfing and the primary and the secondary crosses were as follows:
1. The plants with S₁S₁S₁S₁, S₂S₂S₂S₂, S₃S₃S₃S₃ and S₄S₄S₄S₄ showed a self-and cross-incompatibility in the intra-group crossings among individuals with the same genotype (Table 1).
2. All the possible cross combinations with S_aS_aS_aS_a×S_bS_bS_bS_b types showed compatibility (Table 2).
3. Among six plants with S_aS_aS_bS_b type four with S₁S₁S₂S₂, S₁S₁S₃S₃, S₁S₁S₄S₄ and S₃S₃S₄S₄, showed a self- and cross-incompatibility in the intra-group crossings among the individuals with the same genotype, while the remaining two with S₂S₂S₃S₃ and S₂S₂S₄S₄ were self incompatible (Table 3).
4. In nine cross combinations with S_aS_aS_bS_b×S_aS_aS_aS_a type cross incompatibility were recognized, while six with S_aS_aS_aS_a×S_aS_aS_bS_b type showed cross-compatibility (Table 4).
5. Nine combinations with S_aS_aS_bS_b×S_cS_cS_cS_c type were always cross-compatible (Table 5).
6. Fifteen combinations with S_aS_aS_bS_b×S_aS_aS_cS_c type (Table 6) and five with S_aS_aS_bS_b×S_cS_cS_dS_d type (Table 7) were olso compatible.