Assessment of Diversity among Tropical and Subtropical Maize Inbreds Based on Morphological Traits and Carotenoid Content

The available maize germplasm contains sufficient genetic variability for pro-vitamin A content which could be utilized for development of pro-vitamin enriched varieties aimed at reducing vitamin A deficiency among millions of resource-limited Africans. Fifty-one maize inbred lines from Nigeria and CIMMYT (Zimbabwe) comprising of thirty-seven yellow and fourteen white endosperm types were evaluated in replicated trials at the Institute of Agricultural Research and Training, Moor Plantation, Ikenne and the Teaching and Research farm, University of Ilorin. The objective was to assess the extent of diversity among the inbreds using morphological traits and carotenoid content. The results showed wide variability (P = .05) among the inbred lines for grain yield and other traits as well as total carotenoids. Differences in weather factors in the two locations significantly affected the expression of the traits investigated especially grain yield which recorded the highest deficit in Ilorin due to prolonged drought-stress that occurred at flowering period. Although many of the inbred lines exhibited differential performances for grain yield across the two locations, three inbred lines- BD74-49, BD74-68 and BD74-81 showed consistency in their performance for this trait across the two locations. Significant variation in kernel carotenoid content was also obtained among the 40 maize genotypes investigated. Total carotenoid ranged from 0.03µg/g in the white kernel inbred TZEI 65 to 56.52µg/g in a light orange coloured inbred line BD74-89. The Unweighted Pair Group Method with Arithmetic Averages (UPGMA) dendrogram constructed from the morphological traits clustered the 51 inbred lines into two groups based essentially on their geographical origin, while the dendrogram generated based on total carotenoid content clustered the 40 inbred lines into two major groups with clusters of at least three inbred lines in a sub-cluster. Clustering patterns revealed that lines with high carotenoid content were found in different sub-clusters indicating the feasibility of developing high carotenoid maize varieties from the currently available gene pool.