GENETIC VARIATION, HERITABILITY AND GENETIC ADVANCE FOR YIELD AND AGRONOMIC TRAITS ASSOCIATION OF SOME LOW NITROGEN TOLORANCE MAIZE VARIETIES IN THE TROPICS

Ten open pollinated low nitrogen tolerance maize genotypes were tested using a randomize complete block design at Landmark University Teaching and Research farm in 2016 to 2017 cropping season to estimate the genetic variance, heritability, and expected genetic advance of 12 maize population for grain yield and its component characters. The 10 low N maize populations and 2 checks were evaluated under two different nitrogen regimes 90kg and 30kg of N/ha classified as high N and low N respectively. The study revealed lower phenotypic variances (σ2p) and PCVs relative to genetic variances (σ2g) and GCVs for all the studied characters, suggesting the low influence of environmental factors in the expression of these characters. High degree of genotypic coefficient and phenotypic coefficient of variance, heritability and genetic advance were recorded for grain yield, anthesis silk interval, husk cover, plant height, ear height, plant aspect, days to silking and days to pollen shed. This result suggests that the parameters tested were under the control of additive gene action; and that standard selection protocol may therefore be well appropriate for the improvement of these characters. Moreover, selection of these traits with high degrees of heritability base are predicted to be reliable across different environment in the tropics Lowest value of interval between days to anthesis and silk (ASI) was obtained by BR 9928-DMRSR LN C1. This maize genotypes is a better candidate for the future maize improvement programmes in quest for the development of drought tolerance maize variety in the tropic. Highest maize grain yield were recorded by varieties TZLCOM1C6LNC I (6.19 t/ha) and Sint Marzocalarga (5.26 t/ha) under high N and low N respectively. These two maize genotypes can therefore be suggested for the future maize grain yield improvement programmes in the tropic.