Self-incompatibility related to seedless fruit production in citrus plants.

Self-incompatibility in Citrus species is an important trait related to fruit set and seed formation. In particular, self-incompatible citrus varieties combined with sufficient parthenocarpy produce seedless fruits. The characteristics of self-incompatibility have been studied for many years, and essential traits, such as pollen tube elongation behavior and self-incompatibility genotypes, have been characterized. Recently, it has been shown that the genetic mechanism of self-incompatibility in citrus varieties is S-RNase-based gametophytic self-incompatibility. To date, 18 S-RNases (17 self-incompatible alleles and 1 self-compatible allele) have been identified. The DNA markers for S-RNases can enable the early identification of self-incompatibility/compatibility status. The expression of self-compatibility in Citrus species is ascribed to the presence of the self-compatibility S_m allele, which is a defective S-RNase, and to the suppression of S-RNase expression. Polyploidization induces self-compatibility in Citrus species: Citrus tamurana "Hyuganatsu" is substantially self-incompatible; however, its bud mutation, "Nishiuchi Konatsu", is self-compatible. "Nishiuchi Konatsu" is...