Cultivars of perennial glandular-haired alfalfa, Medicago sativa L., are commercially available for control of the potato leafhopper, Empoasca fabae (Harris). The glandular trichomes secrete an exudate that plays both a chemical and physical role in resistance. Our objective was to assess the influence of trichome age and abiotic factors on the secretory capabilities of the glandular trichomes and consequently leafhopper resistance. We used the resistant cultivar 'G98A' (Cal/West Seeds) and the susceptible nonglandular cultivar 'Ranger'. Influence of trichome age was assessed using no-choice tests by caging adult leafhoppers onto basal and apical stem internodes of each cultivar. Mortality levels were high on the apical internodes of G98A, while no difference was detected among G98A basal internodes, and both apical and basal internodes of Ranger. Quantification of excretory droplets revealed lower levels of feeding on G98A apical internodes than all other treatments. Effects of abiotic factors (temperature and light intensity) on resistance were studied by subjecting leafhoppers to combinations of high and low temperature and light intensities. The highest mortality was recorded on G98A under high temperature and high light intensities. Leafhopper mortality did not differ among the resistant and susceptible plants under the low temperature regime. Resistance appears to be influenced by trichome characteristics, such as secretory capabilities, which in turn are influenced by age, temperature and light conditions.
Species 1: Homoptera Cicadellidae Empoasca fabae (potato leafhopper)
Species 2: Medicago sativa (alfalfa)
Keywords: glandular trichomes, alfalfa
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