Grain yield losses in maize ( Zea mays L.) genotypes in relation to their resistance against Chilo partellus (Swinhoe) infestation at anthesis

Abstract

Resistance/susceptibility of 12 maize genotypes to stem borer Chilo partellus (Swinhoe) (Lepidoptera: Pyralidae) was measured under artificial infestation at the time of anthesis during the short rainy seasons of 1989/90 and 1990/91. The maize genotypes tested were Inbred A (Kenya), Pwani hybrid (Kenya), Hybrid 511 (Kenya), ICZ2-CM (CIMMYT), MBR-8637 (CIMMYT), MBR-8650 (CIMMYT), MBR-8668 (CIMMYT), Poza Rica 7832 (CIMMYT), Mp704 (USDA), Katumani Composite B (Kenya), Bulk CG 4141 (Zambia), and MMV 400 (Zambia). Under low infestation (50–60 eggs per plant), the differences between susceptible and resistant genotypes in terms of stalk damage or grain damage were not apparent, whereas under high infestation (90–100 eggs per plant) the susceptible genotype Inbred A and population Bulk CG 4141 were distinctly more damaged than the remaining genotypes. The genotypes MBR-8637 and Poza Rica 7832 were classed as resistant to C. partellus. A regression of grain yield on stem tunnelling revealed a negative relationship between these factors across maize genotypes, although it was significant only for the susceptible Inbred A and the population MBR-8650. Grain yield of various maize genotypes was also influenced negatively by the damage caused by C. partellus directly to the kernels. Losses suffered by various maize genotypes at low infestation were equal but, under high infestation, significantly more losses occurred on Inbred A than on the remaining genotypes. The maize genotypes MBR-8637 and Poza Rica 7832 were classified as resistant to the second-generation stem borer at anthesis and can be used in a programme for breeding maize resistant to C. partellus.