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 (S ²⁰⁶-homozygote, low RLSICO₂) and LV364 (S ²⁰⁹-homozygote, high RLSICO₂). The RLSICO₂ among three S-genotypes (S ²⁰⁶-homozygotes, S ²⁰⁶ S ²⁰⁹-heterozygotes, S ²⁰⁹-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 S ²⁰⁹-homozygotes with different RLSICO₂ have shown that this gene would act in the stigma.