Soil suppressiveness to Heterodera schachtii under different cropping sequences

Abstract

AbstractHeterodera schachtii population densities were monitored in a H. schachtii -suppressive soil cropped in screenhouse experiments for two consecutive seasons with wheat, susceptible or resistant cultivars of either sugar beet or oilseed radish, or left fallow. Heterodera schachtii population densities under wheat and the resistant cultivars of sugar beet and oilseed radish did not differ significantly from the fallow treatment. Populations declined under all crops, with a reproductive factor between 0.08 and 0.57. In glasshouse experiments, introduced H. schachtii populations increased greatly on susceptible Swiss chard grown in previously wheat-monocultured soils, suggesting that significant loss of H. schachtii suppressiveness occurred during the monoculture. Following fallow, two H. schachtii-resistant or two H. schachtii-susceptible cultivars, introduced sugar beet cyst nematode populations remained small, suggesting that suppressiveness had been maintained. In a field trial with H. schachtii suppressive soil, cyst nematode population densities remained lower under wheat, resistant sugar beet, resistant radish and susceptible radish than under susceptible sugar beet.