Abstract
The soybean cyst nematode (Heterodera glycines Ichinohe) is a serious pest that might be managed by the judicious use of resistant cultivars. Soybean [Glycine max (L.) Merr. ‘Bedford’] was rotated with ‘Forrest’ for 5 yr on a Tiptonville silt loam (Typic Arguidolls) to determine the effect of selection pressure on the reproductive ability of H. glycines and the effect of rotations on seed yield. At the end of the field experiment in 1984, nematode populations were tested in the greenhouse for compatibility with five soybean lines having genes for resistance to H.glycines. Population levels of H. glycines at harvest when Forrest and Bedford were monocultured were not significantly different after the second year. A 2‐yr rotation of Forrest and Bedford reduced cyst populations levels on Bedford at harvest relative to Bedford monoculture, but no rotation scheme reduced nematode population density after growing Forrest. Yields were higher for Bedford than for Forrest in the first 2 yr of the study, but thereafter no rotation was consistently superior. Cyst reproduction in the greenhouse was highest on Forrest and lowest on PI90763. Bedford best differentiated the field‐selected nematode populations in the greenhouse experiment. Reproduction on Bedford was lower if Forrest was grown in the last year of the field experiment than if Bedford was grown, indicating that the frequency of virulence gene(s) was not maintained in the nematode population in the absence of selection pressure.
Published Version
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