Genetic diversity and population structure of farmers' maize varieties (Zea mays L.) from three selected states in Nigeria using SSR markers and their relationship with standard hybrids
Maize (Zea mays L.) is an economically important tropical crop cultivated by farmers in Nigeria. In this study, genetic diversity and population structure were assessed in a set of 19 maize varieties, including most commonly grown maize varieties by farmers in Edo, Ekiti and Kwara states in Nigeria and newly developed hybrids in International Institute of Tropical Agriculture (IITA). The accessions were assayed with 20 SSR flanking markers of previously mapped quantitative trait loci linked with the oil and protein or oil/protein contents. All SSR markers were polymorphic with the mean polymorphism information content value of 0.75. Based on the SSR genotyping data, a total of 183 alleles, ranging from 3 to 18 averaging 9.15 were detected. A moderately high number of unique alleles was present in 3 farmers' varieties (EK04, EK06, KW11) and a hybrid (LW18). The 19 maize varieties were separated into two main groups: 5 varieties clustered in group I; 13 maize varieties clustered in group II but subdivided into two subgroups; The subgroup 1 included four farmers' varieties from Kwara (2) and Ekiti (2) and the remaining 2 were from the IITA while three hybrids (LW17, LW18, and LW19), and four farmers' varieties from Kwara clustered in subgroup 2 in the dendrogram. The one landrace from Ekiti state stood alone in the dendrogram and was distinct from the other farmers' varieties and the newly developed hybrids. The result from the factorial analysis was consistent with the dendrogram and grouping based on states of the collection of farmers' varieties and the newly developed hybrid may be considered substantial. The result of the STRUCTURE analysis classified the 19 varieties as an admixture, indicating one population which was not in accordance with the dendrogram and factorial analyses. The study using SSR analysis has revealed the genetic variation among the farmers' varieties and their genetic relationship with the IITA maize hybrids. The information obtained from the study may form the basis for maize breeding and conservation programs in the future.
Key Words: Maize, Genetic diversity, Population structure, SSR markers