SSR markers reveal genetic variation between improved cassava cultivars and landraces within a collection of Nigerian cassava germplasm

Thirty-one improved cultivars and five Nigerian landraces of cassava were assessed at genomic DNA level with 16 SSR primers for genetic diversity study. The minimum number of SSR primers that could readily be used for identification of the 36 cassava genotypes was also determined. For the genetic diversity study, the similarity coefficients generated between improved cultivars and Nigerian landraces ranged from 0.42 to 0.84, and 12 distinct DNA cluster groups were identified at 0.70 coefficients using Numerical Taxonomy and Multivariate Analysis System software package. For the genotype identification study, the 16 SSR primers were screened by their polymorphic information content (PIC) values. Five SSR primers that have PIC values between 0.50 and 0.67 were selected and further assessed using simple arithmetic progression combination method. The results obtained revealed a combination of these 5 primers from SSR primers collection at IITA that could readily distinguish the 36 cassava genotypes at 0.93 similarity coefficient. These five primers clustered the 36 cassavas into 16 groups at 0.70 similarity coefficient. Application of this few SSR primers would ultimately reduce the cost and time of research for genetic diversity and genotype identification studies for the genetic improvement program of cassava.