Genetic Studies of Grain Yield and other Agronomic Traits of Low-N Maize (Zea mays L.) Using a Diallel Cross under Nitrogen Fertilizer Levels

Abstract

Ten low-N open pollinated maize varieties were converted to inbred line after six generations of selfing and used to study the genetic effects of grain yield and other agronomic traits. The 10 inbred lines were crossed in all possible combinations to generate 90 F1 hybrids (45 crosses and 45 reciprocals). The 90 F1 along with their parents were evaluated at the Teaching and Research Farms of Ekiti State University, Ado-Ekiti and Osun State University, Ejigbo in 2017, using two environments created by levels of N (low and high). The design at each location was a Randomized Complete Block Design (RCBD) with two replicates. Data were collected on plant height, ear height, days to 50% anthesis, days to 50% silking, incidence of curvularia leaf spot, blight, plant aspect, ear aspect, ear rot, stay green, cob per plant, ear weight, grain moisture content and grain yield. All data obtained were subjected to analysis of variance. Specific combining ability (SCA) and general combing ability (GCA) were obtained for the traits. The mean yield of the hybrids (6,444.42 t/ha) and reciprocal (5,971.64 t/ha) were significantly higher than their parents (2,212.84 t/ha). Significant GCA, SCA and reciprocal were recorded for all traits. Hybrids showed better performance compared with parental lines demonstrating heterotic effect. The ratio of GCA/SCA mean square revealed that non-additive gene action was more important for all the traits except ear height, blight, stay green and cob per plant. The estimate of GCA and SCA in this study provides the maize breeder with information to determine which lines to select to improve elite varieties and which parent lines should be used for making hybrids with greater grain yield under condition of low soil N.