Population genetics of self-incompatibility and developing self-compatible genotypes in niger (Guizotia abyssinica)

Niger (Guizotia abyssinica (L. f.) Cass. (Asteraceae) is a strictly self-incompatible crop species with a sporophytic self-incompatibility mechanism. This characteristic presents a number of difficulties in plant improvement programs. The objective of this study was to determine the number and distribution of S-alleles in Ethiopian niger populations and to identify and develop self-compatible genotypes with various associated advantages. Several aspects of self-incompatibility in niger were compared in self- and cross-pollination experiments in which seed-set was considered to be a measure of compatibility. Our results indicate the presence of a minimum of ten self-incompatibility alleles and one self-compatibility allele at the S-locus in niger. Most of these alleles behave differently in the pollen and pistil. About two-thirds of the allelic interactions in both the pollen and pistil were dominant/recessive, and one-third were codominant. The reciprocal cross-pollinations (RCPs) resulted in progeny with similar levels of compatibility within and among populations because of a wide distribution of S-alleles in the populations and, consequently, low population differentiation at the S-locus. An analysis of molecular variance (AMOVA) revealed that only 2% of the total genetic variation at the S-locus differentiates the populations. In conclusion, self-compatible genotypes from the Ethiopian niger gene pool have been identified and developed for the first time.