Relation Between Pubescence of Seedling and Flag Leaves of Winter Wheat and Its Significance in Breeding Resistance to Cereal Leaf Beetle (Coleoptera: Chrysomelidae)

Abstract

Measurements of trichome length and density were carried out on seedling and Hag leaves of 28 winter wheat genotypes over a 2-yr period. Also resistance of genotypes to the cereal leaf beetle, Oulema melanopus (L.), was estimated in 3-yr studies. The genotypes showed very significant differences in both leaf pubescence (≍ 19 times) and leaf-feeding damage of cereal leaf beetle (≍ 10 times). Close correlations were found between data for seedlings and Hag leaves (total trichome length, r = 0.80, P = 0.001; average trichome length, r = 0.69, P = 0.001), except for the trichome density, which did not show a significant correlation ( r = 0.29). On a 1-mm2 surface of the seedlings, many fewer trichomes were found (about one-sixth of those found on the Hag leaves). However, the average trichome length was ≍ 8 times longer than that of the Hag leaves. Ranks of the genotypes did not differ significantly in the 2 yr except for the average trichome length of seedlings. On Hag leaves only, the trichome length provides reliable information about the level of resistance to O. melanopus ( r = -0.76, P = 0.001), but in seedlings, the trichome density is better suited for resistance estimation ( r = -0.52, P = 0.01). These results have application in breeding. From the breeding point of view, the highly significant correlations between seedling and flag leaf pubescence are of utmost importance because it makes screening possible in the seedling stage for Hagleaf pubescence, the most important factor in cereal leaf beetle resistance.