Screening Maize (Zea mays L.) Germplasm For Nonparasitic Weed Tolerance in A Tropical Rainforest Agro-Ecology

Abstract

The study determined genotypic effect of weed infestation on maize germplasm, identified plant traits conditioning weed-stress tolerance, and identified maize varieties that are weed-stress tolerant for further improvement under weed infestation with a view to providing information on the genetics of weed-stress tolerance in maize. The study was carried out at the Teaching and Research Farm of Obafemi Awolowo University, Ile-Ife, in the early and late rainy seasons of 2018. One hundred open-pollinated maize varieties of different maturity groups, obtained from the International Institute of Tropical Agriculture (IITA), Ibadan, were planted in three experiments covering a total of five environments between May and September, 2018, each in a 10 x 10 lattice design with three replications. Experiment 1, planted in two environments, involved the planting of the 100 maize varieties without any form of weeding from planting till harvesting. Experiment 2 involved one environment and two treatments: (i) no weeding at all from planting till harvesting; (ii) clean weeding from planting till harvesting. Experiment 3 involved two environments and three treatments: (i) no weeding at all from planting till harvesting; (ii) clean weeding from planting till harvesting; (iii) use of pre-emergence herbicides and no weeding thereafter. Data were collected on emergence, vegetative and flowering traits as well as grain yield and its components. Analysis of variance (ANOVA) was done from which variance components were obtained and used to estimate broad sense heritability on entry mean basis for each trait. Relationships among all the measured agronomic traits were determined using Pearson correlation analysis and cluster analysis was also done to classify the varieties into groups having similar performance across some of the traits. The weed-stress tolerant varieties were selected using rank summation index. xvi Results of analysis of variance (ANOVA) showed that under uncontrolled weed stress, there were highly significant mean squares (p