valuation for resistance to the spotted stem borer, Chilo Partellus, in a maize (zea mays L.) population. Maize Production Technology for the Future: Challenges and Opportunities. Proceedings of the Eastern and Southern Africa Regional Maize Conference, 6; Addis Ababa (Ethiopia); 21-25 Sep 1998.

Abstract

AGenetic variability and predicted responses to S2 and testcross selection methods were studied in an open-pollinated variety resistant to the spotted stem borer,(Chilo partellus Swinhoe). Evaluation after one cycle of selection for grain yield and parameters of resistance to the borer were investigated. Genetic variances and heritability estimates were moderate to high for the S2 progenies with heritability estimates being higher for the agronomic traits compared to the parameters of resistance. Generally, more gain/cycle of selection was achieved through single trait selections than by index selection. Percentage gains for single trait selections ranged from-67.18% to-31.40% for dead heart and 23.21% to 7.90% for grain yield of the S2 andtestcross hybrids, respectively. For the aggregate trait, gains per cycle (percentage) ranged from-96.01% to-48.45% for dead heart and 7.45% to 2.90% for stem tunnelling for the S2 and S2 testcrosses, respectively. Predicted direct responses (Ag/cycle) to aggregate trait selections for both the grain yield and parameters of resistance showed no significant differences for the two progeny types except for stem tunnelling.