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|Title:||The Potato Leafhopper, Empoasca Fabae, Soybean Pubescence, and Hopperburn Resistance|
|Department / Program:||Entomology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||To determine the detailed interactions between soybean pubescence, potato leafhopper, and onset of hopperburn, a series of experiments was carried out with using field and laboratory colonies of the PLH, and 4 near isogenic soybean cv. 'Clark' differing in the nature of the trichome cover.
Scanning electronmicrographic analyses revealed that the PLH has a unique pretarsal structure that tips of pulvilli are modified to form a "suction-cup" and claws are very much reduced and apparently non-functional. Process of the primary orientation is described in three steps: (1) Press the tip of pulvilli against the substrate; (2) moistening pulvillar/substrate interface; (3) create a vacuum within the interface, and provide a firm attachment. Release of legs by relaxation and equalization of the pressure inside and outside of the interface. PLH is ill-suited to move and assume a normal primary orientation on pubescent plant's surfaces, which would greatly hamper both feeding and oviposition behavior.
PLH nymphs feed and grow to maturity on pubescent soybean leaves, mainly feeding on blades. The rate of feeding and oviposition were much lower on normal and dense pubescent lines than on glabrous plants. However, those rates increase a lot if PLH was on a shaved part of the same plant.
Hopperburn was never observed on normal or dense pubescent 'Clark' soybean. However, the symptom developed on the same plants if trichomes were removed by shaving before the exposure to PLH.
Significantly more trichomes cover the veins than the blades of the same leaf which places the phloem beyond the reach of the PLH. Therefore, the mechanism of hopperburn resistance by trichomes is simply due to a physical barrier (not a chemical) interfering with the ability of the PLH to feed on the phloem. The barrier effect of the trichome layer is formed by the thickness of the indumentum which is a function of trichome density, length, angle of insertion, and shape of trichomes.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.
|Date Available in IDEALS:||2014-12-16|