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

Abstract

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 selfand 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 selfincompatibility alleles and one self-compatibility allele at the S-locus in niger. Most of these alleles behave differently in the pollen and pistil. About twothirds 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, selfcompatible genotypes from the Ethiopian niger gene pool have been identified and developed for the first time.

Variability in seed oil content and fatty acid composition, phenotypic traits and self-incompatibility among selected niger germplasm accessions

“…These findings are consistent with Riley and Belayneh (1989) when they reported that niger has a small degree of self-compatibility though the plants may not necessarily be truly selfcompatible. A previous study by Geleta and Bryngelsson (2010) found that niger is a strictly self-incompatible crop of sporophytic nature, though nine plants out of the 340 evaluated showed some degree of compatibility.…”

“…The pollen–stigma reaction results in callose production (Takayama and Isogai, 2005). In dicots, self-incompatibility (SI) is mapped to a single genetic locus called the S-locus (Geleta and Bryngelsson, 2010).…”

Patterns of domestication in the Ethiopian oil‐seed crop noug (Guizotia abyssinica)

“…Nevertheless, only a small proportion of genetic variance ( F st = 0.044) occurred among noug populations. Genetic exchange between different noug accessions is facilitated by the fact that the crop has a self‐incompatibility system and is obligately outcrossing (Geleta and Bryngelsson ). Crops with self‐incompatibility systems are known to be more challenging to improve through breeding, as it is difficult to keep lines of interest ‘true to type.’ If an interesting phenotype is discovered in a certain accession, there is a high risk that the phenotype of interest will no longer be present in the next generation, as maintenance of the genetic identity of the line through selfing is not possible.…”

Evidence for Selection on a Chordate Histocompatibility Locus

“…Patterns at SI loci are similar to those at het/vic and FuHC. In G. abyssinica (niger), 97% of the SI locus variation was found within populations, and F ST values were very low (although statistically significant) (Geleta and Bryngelsson 2010). F ST values are significantly lower when compared to neutral loci, in all cases ( A. lyrata: Kamau et al 2007; A. halleri: Ruggiero et al 2008; B. cretica: Edh et al 2009; B. insularis: Glemin et al 2005).…”