Abstract

This study seeks to determine the genetic diversity among cassava landraces using single nucleotide polymorphic (SNP) markers. One hundred and five cassava landraces were assayed with 195 SNP markers. Major allele frequency varied from 0.500 to 0.942 with an average of 0.728. Average gene diversity, heterozygosity and polymorphic information content (PIC) were 0.359, 0.314 and 0.286 respectively. These values were generally high considering the bi-allelic nature of SNPs, hence the cassava landraces studied showed moderate to high genetic diversity. This suggests availability of unique and useful alleles that could be exploited for breeding purposes. Inclusion of these landraces in our crop improvement activities will enhance the development of farmer preferred cassava varieties. SNP markers used for the study were highly informative, polymorphic and revealed good estimates of genetic diversity among the landraces. Higher level of genetic variation was observed within population based on analysis of molecular variance (AMOVA). Principal component analysis (PCA) and cluster analysis also grouped landraces into three distinct clusters; however, they did not group in accordance to geographical origin. This could be due to high frequency of germplasm exchange between farmers and subsequent change of the name of the same cultivar. Results from this study may contribute significantly to cassava breeding and germplasm conservation programs.

Key words: Genetic diversity, single nucleotide polymorphisms (SNPs), polymorphic information content (PIC), polymorphic, alleles, heterozygosity, germplasm.