|MCCASLIN, MARK - FORAGE GENETICS
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/1997
Publication Date: N/A
Interpretive Summary: Development of alfalfa germplasm resistant to the potato leafhopper, the major insect pest of alfalfa, has met with limited success. Selected plants from an alfalfa population developed for potato leafhopper resistance, based on the presence of glandular hairs, were evaluated in the laboratory to quantitate and determine the relationship of glandular hairs with potato leafhopper resistance. The results demonstrated that a relationship exists between glandular hair density and high levels of potato leafhopper resistance and suggest that the glandular hairs present on the selected clones used in this study are associated with a compound which is toxic to the potato leafhopper. Preliminary field evaluations of alfalfa populations from which the selected clones in this study were derived indicate that the first alfalfa cultivars with potato leafhopper resistance, associated with glandular hairs, will be available within the next three years. This study will aid the alfalfa seed industry in incorporating potato leafhopper resistance into their best adapted cultivars and provide growers with a means of control which will reduce production costs and adverse environmental impacts.
Technical Abstract: Perennial glandular-haired alfalfa (Medicago) species and hybrids have been implicated with resistance to the potato leafhopper, Empoasca fabae (Harris). However, the development of potato leafhopper resistant alfalfa germplasm utilizing the glandular hair trait has met with limited success. The objectives of this study were to quantitate and determine the association of glandular hairs with potato leafhopper resistance in nineteen selected clones from an alfalfa population developed for improved vigor and disease and potato leafhopper resistance. The density of glandular hairs on the leaf midveins, petioles, and stems were measured. Selected clones were screened in a laboratory no-choice test for resistance to adult potato leafhopper feeding damage, survival, and oviposition. Differences in glandular hair densities among clones were highly significant for all plant parts measured. Significant variation was observed among clones for all potato leafhopper resistance variables measured. Percent adult mortality ranged from 13 to 96 and nymphal populations ranged from 0 to 33. Associations beteen glandular hair densities on petioles and stems with all the potato leafhopper resistance variables were signigicantly correlated. Results of this study suggest that the glandular hairs present on the selected clones used in this study are associated with a compound which is toxic to the potato leafhopper. This study demonstrates that the glandular hair trait is potentially useful in developing potato leafhopper resistant cultivars.