Efficacy of the fungi Hirsutella minnesotensis and H. rhossiliensis from liquid culture for control of the soybean cyst nematode Heterodera glycines.

摘要

Hirsutella minnesotensis and H. rhossiliensis are endoparasites of nematodes, and their biological control potential against Heterodera glycines when cultured and applied on corn [maize] grits has been reported. In this study, the potential of liquid cultures of the two fungi was evaluated in two glasshouse experiments. Both liquid culture at 0.2, 0.4 and 0.8 g of fresh mycelium/300 cm3 soil (per pot) and solid culture at 1% (corn grits:soil, w/w) reduced nematode egg population densities in both autoclaved and unheated soils compared with soil-only control or corn-grits control. However, the liquid culture at 0.2-0.8 g of mycelium/pot appeared to be more effective in reducing the nematode population than the solid culture of 1%. Hirsutella rhossiliensis resulted in lower nematode population density than Hirsutella minnesotensis only in unheated soil in one experiment. The soil heat treatment generally increased the nematode population density but did not affect percentage reduction of the nematode population density compared with the respective controls, except that reduction by Hirsutella rhossiliensis was greater in unheated soil than heat-treated soil in one experiment. Percentage of second-stage juveniles parasitized by the fungi at the end of the experiment (60 days after planting) was generally higher with Hirsutella minnesotensis than with Hirsutella rhossiliensis. The percentage parasitism was positively correlated with initial fungal inoculation level. The soil heat treatment increased fungal parasitism in one experiment but not in the other. Plant growth was unaffected by the treatments, except that the soil heat treatment increased plant shoot weight compared with unheated soil in one experiment..