Empirical Assessment of the Genetic Diversity of Local Cassava Germplasm in the South South Zone of Nigeria Using SSR Markers

Local cassava germplasm in South South Nigeria harbours genetic diversity relevant to breeding for regional biotic and abiotic stress adaptation, and molecular characterisation using SSR markers provides a more reliable diversity assessment than morphological data alone. This study empirically assessed the genetic diversity of 40 local cassava accessions collected from Rivers, Akwa Ibom, and Bayelsa States using 12 simple sequence repeat (SSR) markers. Leaf samples were collected from georeferenced plants during field collection expeditions, and DNA extraction and PCR amplification were conducted at the University of Port Harcourt Molecular Biology Laboratory. Genetic diversity parameters including allele frequency, PIC, observed heterozygosity, and genetic differentiation (Fst) were calculated. Cluster analysis using UPGMA and principal coordinate analysis were applied to characterise diversity structure. Results revealed a mean PIC of 0.61 across 12 markers, indicating high discriminatory power. A total of 87 alleles were detected with an average of 7.25 alleles per locus. UPGMA clustering divided the 40 accessions into three main clusters without strong geographic correspondence, suggesting widespread seed exchange between communities. Three accessions (from Ogoni, Itsekiri, and Ijaw communities) formed outlier clusters indicating unique genetic backgrounds potentially relevant to salt tolerance breeding. The study provides the first molecular diversity characterisation of South South Nigerian cassava landraces and recommends these three outlier accessions for phenotypic characterisation for salt tolerance before inclusion in IITA breeding crosses.

Keywords: cassava genetic diversity, SSR markers, South South Nigeria, germplasm characterisation, molecular markers