Genetic analysis of the reaction level of self-incompatibility to a 4% CO2gas treatment in the radish (Raphanus sativus L.).

In radishes, self-incompatibility (SI) is governed by the S-locus, which co nsists of a series of multiple alleles. This SI can be overcome by CO2 gas treatment, a characteristic that is very useful in obtaining large amounts of parental seeds for F-1 commercial seeds. We know from experience that th ere are genetic variations in the reaction level of self-incompatibility (R LSI) to a 4% CO2 gas treatment thereafter described as RLSICO2) in the radi sh. We have raised and analyzed an F-2 population derived from an F-1 cross between No. 9324 (S-206-homozygote, low RLSICO2) and LV364 (S-209-homozygo te, high RLSICO2). The RLSICO2 among three S-genotypes (S-206-homozygotes, (SS209)-S-206 heterozygotes, S-209-homozygotes), which fit the theoretical ratio of one gene segregation in the F-2 population, did not show any signi ficant statistical differences. Hence, we concluded that the RLSICO2, was c ontrolled by a gene other than the S-gene. In this F-2 population the segre gation of the RLSICO2, fit the 3(low RLSICO2):1(high RLSICO2) ratio well. T his result and F-3 progeny tests suggest that high RLSICO2 is controlled by a recessive gene. Reciprocal crosses among S-209-homozygotes with differen t RLSICO2 have shown that this gene would act in the stigma.