Estimation of genetic diversity of germplasm used to develop insect-pest resistant maize

Genetic diversity is important in ensuring viability of germplasm for a breeding program. The objective of this study was to determine the genetic diversity of 130 S families from two populations; stemborers’ resistant and storage pests’ resistant populations, each with 65 lines; using 30 simple sequence repeats (SNP) molecular markers. The markers were found to be polymorphic with 0.46 - 0.48 polymorphism for both populations, except locus umc1367, which was monomorphic for storage pests’ resistant population. A total of 109 alleles were recorded from stemborers’ resistant population. Allele’s scores ranged from 2 to 6 alleles per locus, with a mean of 3.6, and product length ranging from 47 bp to 362 bp. The storage pests’ resistant population had a total of 103 alleles, with scores of 1 to 6 per locus, and a mean of 3.4 alleles; and product length of 47 - 320 bp. Observed gene diversity was 0.27, with expected gene diversity of 0.45 for stem borers’ resistant population and 0.48 storage pests’ resistant population. Mean polymorphism information content values ranged from 0.46 to 0.48, while unbiased expected heterozygosity ranged from 0.4 to 0.45 for both populations. Cluster analysis revealed three major clusters in each population; with cluster 1 comprising 34 - 40% of the genotypes in both populations. Cluster 2 had 55% for stem borers’ resistant genotypes, and 53% of storage pests’ resistant genotypes. The study indicates that there is ample genetic diversity in both populations which can be exploited in extracting new inbred lines for use in breeding insect resistant maize hybrids.