Author
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NOEL, GREGORY |
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Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/21/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Soybean cyst nematode, Heterodera glycines, is the most important pest of soybean in the north central U.S. Juveniles hatch from eggs, locate soybean roots, and penetrate roots to establish a feeding site. The mechanism by which eggs are stimulated to hatch is not known. The research reported in this paper demonstrates unequivocally that chemical signals from soybean roots stimulate the nematode to hatch. This research also demonstrates that in order for maximum hatch to occur the nematode must undergo overwintering dormancy. The resistant cultivar Fayette stimulated less hatch than the susceptible cultivars, indicating that the resistance mechanism also involves a reduced ability of the resistant soybean to stimulate hatch of soybean cyst neamtode. Knowledge of soybean cultivar differences in stimulation of hatch and emergence of H. glycines may aid in decisions for long-term control of the nematode. For intstance, ,susceptible cultivars which stimulate more hatch of the nematode in the spring should be avoided as increased hatch would subsequently lead to larger numbers of nematodes infecting plants and larger end of season populations. These populations would then require longer crop rotation sequences to reduce nematode populations to levels which would not cause yield loss to soybean. Technical Abstract: Egg hatch and emergence of second-stage juveniles (J2) of Heterodera glycines races 3 and 4 from cysts exposed to soybean root leachate of cv. Fayette (resistant to H. glycines) and H. glycines-susceptible cultivars A2575, A3127, and Williams 82 were determined in three sets of experiments. In the first experiment, cysts of both race 3 and race 4 were exposed to leachate of 8-week-old plants for a 2-week period. In the second experiment, cysts from populations of race 3 and 4 were raised on cultivars A2575, A3127, and Williams 82. Cysts then were exposed to leachate from 8-week-old plants for a 2-week period in all possible race/cultivar combinations. In the third experiment, cysts of races 3 and 4 were exposed at 4-day intervals to leachate from plants as the plants developed 7-59 days after planting. In experiments 1 and 2 leachate from 8-week-old Williams 82 and A3127 stimulated more hatch and emergence of H. glycines than leachate from A2575, Fayette, or the control. In the first experiment cumulative hatch and emergence were greater for race 3 than race 4. In experiment 2 there was no apparent relationship between leachate from a cultivar and the population developed on that cultivar in terms of stimulation of hatch and emergence. In the third experiment A2575 stimulated more hatch and emergence of both race 3 and race 4 than A3127, Fayette, and Williams 82. Leachate from Fayette stimulated less hatch and emergence of both race 3 and race 4. Hatch and emergence were greatest during the initial 12 days of the experiment. |
