Revealing the genetic diversity of maize (Zea mays L.) populations by phenotypic traits and DArTseq markers for variable resistance to fall armyworm

The fall armyworm (FAW) is a gregarious insect pest causing substantial yield losses and crop failures in maize and related cereal crops in sub-Saharan Africa due to a lack of resistant varieties and integrated control options. Genetic variation for economic traits including resistance to the FAW damage is a prerequisite in maize improvement programs. The objective of this study was to determine the genetic diversity of 59 maize genotypes of diverse genetic background with variable resistance to fall armyworm, using phenotypic traits and SNP-based DArT markers. The test genotypes were profiled using agro-morphological traits, FAW damage parameters, and Diversity Array Technology Sequencing-derived single nucleotide polymorphism (SNP) markers. Significant (p < 0.001) differences were observed among the genotypes for 13 phenotypic traits with phenotypic coefficient of variation ranging from 2.19 to 51.79%. Notable phenotypic variation was observed for ear position, grain yield, FAW induced leaf and cob damage. The mean gene diversity and polymorphic information content were 0.29 and 0.23, respectively, reflecting a moderate level of genetic variation among the test genotypes when assessed using SNP markers. Analysis of the molecular variance revealed greater genetic variance within a population rather than between populations. Population structure and cluster analysis grouped the test populations into two main clusters. The following genetically divergent open pollinated varieties were selected with favourable agronomic performance and FAW resistance for population improvement or hybrid breeding: Pool 16, ZM 4236 and ZM 7114. The genetic diversity detected within and among the tested populations will facilitate the breeding of maize varieties incorporating farmer-preferred agronomic traits and FAW resistance in Zambia and related agro-ecologies.