GENETIC VARIABILITY FOR YIELD AND RESISTANCE TO MAIZE WEEVIL (Sitophilus zeamais) IN TWENTY TWO MAIZE (Zea mays L.) INBRED LINES

Abstract

The maize weevil (Sitophilus zeamais MOTS.) is one of the most important storage pests of maize in sub-Saharan Africa. Developing resistant varieties has been identified as an important and environmentally friendly aspect of the integrated pest management system. However, little is known about the genetic control of resistance to the maize weevil. Hence, this study aimed at providing genetic information on the nature and magnitude of variation for yield and resistance to maize weevil in twenty-two maize inbred lines. Field experiment was carried out at the Teaching and Research Farm (TR&F) of the Federal University of Technology, Akure under rainfed conditions during the 2018 and 2019 cropping seasons to estimate analysis of variance (ANOVA), phenotypic and genotypic coefficients of variation, heritability in broad sense and genetic advance for yield and yield attributes in twenty-two maize inbred lines. The experiment was laid out in a Randomized Complete Block Design with three replications. Data were collected on plant stands per plot, days to 50% silking, days to 50% tasselling, plant height, ear height, number of plants at harvest, number of ears at harvest, moisture content, field weight and grain yield. Seeds obtained from the twenty-two inbred lines were evaluated in the laboratory of the Department of Crop, Soil and Pest Management, FUTA for resistance to maize weevil in a Completely Randomized Design replicated 3 times. Data was collected on percentage weight loss, percentage grain damage, F1 weevil progeny emergence, median development period and susceptible index. Results showed significant differences (P < 0.05) among inbred lines for all traits evaluated in both 2018 and 2019. Also, the year (Y) effect was significant for all traits except for field weight while genotype by year interaction (GxY) was significant for all traits. High heritability coupled with high genetic advance observed in plant stands per plot, number of plants at harvest, number of ears at harvest, field weight, and grain yield indicated the additive nature of their inheritance. Significant positive correlations existed between grain yield and plant stands per plot (rg = 0.33; 0.86) number of plants at harvest (rg= 0.69; 0.95), number of ears at harvest (rg = 0.73; 0.95), and field weight (rg = 1.00; 1.00) for both years, respectively. Thus, the presence of variation could serve as a basis for selection for yield improvement in maize. The overall performance of the inbreds was higher in 2019 relative to 2018. However, TZISTR1259 (1.06 tons ha-1) and TZISTR1190 (1.13 tons ha-1) were consistently high yielding, and recorded higher yields than the average mean yields in both years, suggesting relative stability of performance. The Dobie index of susceptibility was used to group the inbred lines. Eighteen of the inbred lines were found to be moderately susceptible while the remaining four were susceptible. RSI identified TZISTR1162 as the most promising inbred alongside TZISTR1244, TZISTR1160, TZISTR1190 and TZISTR1163in terms of higher yield and resistance to maize weevil. Therefore, it is recommended that TZISTR1162, TZISTR1244, TZISTR1160, TZISTR1190 and TZISTR1163 could be used as breeding materials for improvement programs and in raising promising cultivars for higher yield and resistance to maize weevil.