Genetic variability and diversity in okra landraces using agromorphological traits and seed elemental minerals

Okra [Abelmoschus esculentus (L.) Moench] landraces found in Nigeria are being examined as sources of genetic variation offering potential to improve agro-morpho-nutritional traits and broaden the gene pool. Objectives of this investigation were to: (1) assess variability of agro-morpho-nutritional traits in okra landraces sourced from five agroecological zones in Nigeria, and (2) estimate divergence among the germplasm. The landraces were evaluated in field experiments over a period of 2 years at the research farm of the Federal University of Agriculture, Abeokuta, Nigeria. Principal component analysis, cluster analysis, and Mahalanobis D2 statistics were employed to study the diversity pattern. Differences existed for all evaluated traits among landraces. Genotypes NGB00378b, NGB00297, NGB00347, NGB00293, and NGB00350 combined high seed mineral concentrations with high yield potential. A genotype × year interaction was present, as reflected by relatively low broad-sense heritability (<30%) and genetic advance (GA) (<10%) for pod yield and pod width (PDW), which limits potential for improvement. Heterosis breeding could be effectively used to improve K and Mg, as these traits expressed high variation and broad-sense heritability coupled with moderate GA. Using D2 divergence analysis, landraces were separated into seven distinct clusters, with no phylo–agroecological pattern of diversity. Based on the present study, selection for a trait in 1 year may not provide the same benefit in other years due to year-to-year fluctuations in environmental conditions, evaluation in more than 1 year is required.