Genetic diversity and morphological characterization of African nightshade entries (section Solanum L.)

Abstract

African nightshade is an indigenous leafy vegetable in sub-Saharan Africa valued for its high nutrient content and therefore provide nutritional security and also potential to generate income especially to small scale farmers. Production is however below potential due to lack of superior varieties that are high yielding and tolerant to environmental stresses. Development of varieties through breeding programs has been initiated in order to supply farmers with quality seeds. The efforts to improve this crop however have been hampered by limited information available on intra- and interspecific genetic diversity. In this study new SSR markers developed using next generation sequencing and AFLP markers were used to assess genetic diversity and differentiation in 54 African nightshade entries. The genotypes comprised entries of two species, Solanum scabrum (Mill.) and S. villosum (Mill.) including developed lines and farmer cultivars. Morphological traits relevant for agronomic performance of the entries were also analysed. In addition to the diversity studies, the genome size and pollen viability parameters were determined. The molecular markers clearly distinguished the two species and S. scabrum was found to be less diverse as compared to S. villosum. Farmer cultivars had higher allelic richness and a larger number of unique alleles than developed lines. Analysis of molecular variance showed higher variation within than between entries. Cluster analysis grouped the entries into two clusters representing the two species. The analysis of agronomic traits revealed significant differences between entries. All entries of S. scabrum were found to be hexaploid whereas entries of S. villosum were tetraploid with a haploid genome size of all samples slightly varying around 1pg. Pollen viability parameters significantly differed between the two species but did not correlate to any of the other parameters measured in this study.