Resistance of winter wheat to cereal leaf beetle (Coleoptera: Chrysomelidae) and bird cherry-oat aphid (Homoptera: Aphididae)

Resistance tests based on estimation of leaf-feeding damage by cereal leaf beetle, Oulema melanopus (L.), and infestation by bird cherry-oat aphid, Rhopalosiphum padi (L.), were conducted on 26 winter wheat genotypes over a 3-yr period. Grain yield and thousand-kernel mass were measured in infested and non-infested control plots in cages covered by insect nets. Highly significant differences were found between genotypes in feeding damage by cereal leaf beetle and infestation by bird cherry-oat aphid. The most resistant genotype had 7.4% leaf-feeding damage by cereal leaf beetle and the most susceptible 69.4%. Values of infestation by bird cherry-oat aphid varied between 25 and 79.2%. Yield response was more sensitive indicator of genotype reaction than the 1,000-kernel mass. Yield of the most tolerant genotype was reduced by 26%, whereas the 1,000-kernel mass was reduced only 23%. The maximum losses were 63% in yield and 50% in 1,000-kernel mass. A close correlation was found between infestation severity by bird cherry-oat aphid and yield reduction (r = 0.7572), but feeding by cereal leaf beetle did not significantly affect yield. Trichome length of the flag leaf exhibited a significant correlation with feeding damage by cereal leaf beetle (r = -0.7161), but neither trichome density nor length influenced the infestation by aphids. Principal components analysis and multiple regression analyses were performed to determine the relationships among tested characteristics and to quantify the effect of leaf-feeding damage by cereal leaf beetle, infestation by bird cherry-oat aphid, Fusarium spp. infection, heading date, and plant height on grain yield and 1,000-kernel mass. Among the variables examined, infestation severity of R. padi had the highest relative importance and direct effect on both yield reduction and 1,000-kernel mass.