Screening some maize genotypes for grain yield and plant tolerance to spotted stem borer (Chilo partellus Swinhoe)

An experiment was conducted under irrigation at the Gezira Research Station, Wad Medani, Sudan, for two cropping seasons (autumn and winter) during 2005/2006. The objectives were to study the genetic variability for grain yield and assess tolerance to stem borer infestation using a large maize germplasm. The experimental material consisted of 42 maize genotypes obtained from the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, the International Institute of Tropical Agriculture (IIT A) in Nigeria and Sudan. The plants were subjected to natural infestation by the spotted stem borer (Chilo partellus Swinhoe). Growth, grain yield and stem borer tolerance traits were measured. Most of the studied traits showed significant differences among the 42 genotypes. High to moderate broad sense heritability estimates (0.85-0.25) were shown by these traits. The genotypes gave higher yields in autumn than in winter probably due to the favorable environmental conditions of the rainy season and the lighter infestation by the stem borer. IIT A material gave the highest and lowest grain yields in autumn and winter, respectively. The opposite was true for CIMMYT material. The highest yielding genotypes in autumn were MH0102-4, (4.8 t/ha) and MH0I02-3, (3.92 t/ha), while in winter were CKIR05002, (2.33 t/ha) and CKIR04005, (2.31 t/ha). Hudeiba-l was a high yielding stable variety throughout the two seasons. CIMMYT material showed the highest tolerance to stem borer infestation particularly CKIR 04002 and CKIR 05009. Grain yield was highly and negatively (r -0.70**) geno¬typically correlated with the earliness traits as well as the stem borer tolerance indicators. The very highly significant negative association of grain yield with the stem borer tolerance traits may be due to their relatively high and negative indirect effects via days to 50% silking ( -¬0.40). The percentage of infested plants/plot was the most suitable trait that could be used as selection criterion for stem borer tolerance