MECHANISMS OF POTATO LEAFHOPPER RESISTANCE IN SOYBEAN LINES ISOGENIC FOR PUBESCENCE TYPE

Seldom is the potato leafhopper (PLH) [Empoasca fabae (Harris)] a problem on the pubescent soybean [Glycine mar (L.) Merr.) cultivars that currently dominate U.S. production. The questions remain, however, whether a higher level of resistance is needed and if alternative mechanisms of resistance are available to combat this potential insect pest. The objectives of this study were to investigate the influence of soybean lines isogenic for pubescence types on PLH feeding damage and oviposition and to determine if the mechanisms of resistance in foliar-feeding insect resistant breeding lines are effective against the PLH. Soybean lines isogenic for dense, normal, and glabrous pubescence, developed from the genotypes 'Davis', 'Tracy-M', and D75-10169 were subjected to free-choice and no-choice laboratory studies to identify specific mechanisms of PLH resistance. The normal and dense pubescent isolines caused a significant reduction in feeding damage, oviposition, and subsequent nymphal populations when compared to glabrous isolines. Dense pubescence resulted in an additional significant reduction in feeding damage and a significant increase in adult mortality. Results indicate that normal pubescence, similar to that found in most soybean cultivars grown in the USA, provides a high level of resistance to the PLH. Besides mechanisms of resistance due to pubescence, this study also identified PLH feeding and oviposition nonpreference types of resistance, not associated with pubescence, in the breeding line D75-10169, a genotype breed for resistance to foliar feeding insects.