Improvement of a stem borer resistant maize population for nitrogen deficient environments
Nitrogen (N) deficiency is a common feature in all maize growing ecologies of West and Central Africa. It is therefore imperative to produce maize varieties that are able to survive in N deficient environments. To determine their potential in improving the population for N deficient environments, S1 progenies from a stem borer resistant maize population- BR9928DMRSRLNC1 were evaluated under low soil N (30kgN/ha) condition at Mokwa and Zaria, Nigeria in 2013. Furthermore, the original and improved cycle of the population were later evaluated at the same test locations under two additional N fertilizer levels (0kg and 90kgN/ha), to estimate gains from selection. Several traits were evaluated. For most of the traits studied, genetic variability was moderate to low and ears per plant, ear aspect and plant height were significantly correlated with yield. Step-wise multiple regression, identified ears per plant and ear aspect as having high direct effects on grain yield. Expected gains per cycle were lower than observed for most traits except grain yield and plant height. Comparison between the original and improved cycle revealed that in general, selection reduced days to flowering and ear aspect ratings across all N levels. In addition, grain yield increments were observed in all N environments with the most significant change of 15% occurring at 90kgN/ha. Using a weighted index with larger weights assigned to grain yield, ear aspect and ears per plant should increase gain in further selection programs.
Keywords: Nitrogen deficiency; maize; genetic variability; genetic gain; S1 progeny selection