Assessing Relationships in Kenyan Sorghum Landraces by Use of Simple Sequence Repeat Molecular Markers

Abstract. In the semi-arid areas of Kenya, the effects of climate change are accelerating the genetic erosion of many crops and threatening food security of resource-poor farmers. This study analyzed the genetic diversity of the available Sorghum bicolor L. germplasm using simple sequence repeat (SSR) markers with the aim of identifying varieties that can be selected to meet food security needs of these marginal environments. Accessions from four agro-ecological regions were genotyped with 39 SSR markers chosen on the basis of their position in the genome and the large repeat sizes they represented. The alleles were called using the Gene Mapper software (version 3.7), sizes assigned with the allelobin software and the subsequent data analyzed with the Power Marker software (version 3.25). The Arlequin software (version 2.0) was used to calculate the diversity indices and the intra-population structure. Genetic distances were calculated according to Rogers modified distance and the accessions were clustered using principal component analysis (PCA). A mean polymorphic information content (PIC) value of 0.536 was observed, indicating moderate levels of polymorphism. The variability within accessions among the populations was 56.37%, within individual accessions was 38.85% and among geographical origins was 4.78%. A low level of genetic differentiation (FST = 0.048) and a high inbreeding level (FIS = 0.59) showed an increased degree of allele fixation. The results showed that though most of the accessions were similar, there was sufficient genetic diversity among and within sorghum landraces in Kenya, which would be useful in the improvement of sorghum productivity.