Genetic analysis for resistance to Sitophilus zeamais (Motschulsky) among provitamin-A maize germplasm

Abstract

Maize biofortification is adopted as strategy to circumvent the high risk of vitamin A deficienc, accentuated by high incidence food losses due to storage insect pests in most developing countries where maize is an important staple crop. This study was initiated to understand the mode of inheritance for resistance to storage weevils among provitamin-A germplasm. A total of 72 provitamin-A maize testcross hybrids were evaluated for agronomic and adaptive traits in three sites, Namulonge, Serere and Ngetta in Uganda during the main season of 2015. Based on genotype x environment analysis of field traits, resultant grain from two divergent environments (Namulonge and Serere) were screened for resistance against Sitophilus zeamais in a no-choice laboratory. Line by tester analysis of combining ability indicated that both additive and non-additive gene effects were important in controlling the resistance parameters, including adult mortality, F1 insects which emerged, Median Development Period, Index of Susceptibility and Grain damage. Two provitamin-A inbred lines, CLHP0014 and CLHP0005 showed high GCA effects for reduced infestation with storage weevil. Broad sense heritability was moderate (0.19 ≤ H2 ≤ 0.59) and Narrow sense heritability (h2) was low ranging from 0.19 to 0.24. The two inbred lines with desirable GCA effect for weevil resistance could be used in the development of resistant breeding population. However, the low heritability of the trait observed, suggested that effective breeding methods be deployed to increase resistance to storage weevil, concurrently with research efforts to develop high nutritional quality maize varieties.