Genetic analysis of the reaction level of self-incompatibility to a 4% CO2 gas treatment in the radish (Raphanus sativus L.).

Abstract

In radishes, self-incompatibility (SI) is governed by the S-locus, which consists 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 F1 commercial seeds. We know from experience that there are genetic variations in the reaction level of self-incompatibility (RLSI) to a 4% CO2 gas treatment (hereafter described as RLSICO2 ) in the radish. We have raised and analyzed an F2 population derived from an F1 cross between No. 9324 (S206-homozygote, low RLSICO2) and LV364 (S209-homozygote, high RLSICO2). The RLSICO2 among three S-genotypes (S206-homozygotes, S206S209-heterozygotes, S209-homozygotes), which fit the theoretical ratio of one gene segregation in the F2 population, did not show any significant statistical differences. Hence, we concluded that the RLSICO2 was controlled by a gene other than the S-gene. In this F2 population the segregation of the RLSICO2 fit the 3(low RLSICO2):1(high RLSICO2) ratio well. This result and F3 progeny tests suggest that high RLSICO2 is controlled by a recessive gene. Reciprocal crosses among S209-homozygotes with different RLSICO2 have shown that this gene would act in the stigma.