Nematophagous Hyalorbilia spp. isolated from Heterodera schachtii in California parasitize Heterodera glycines

The goal of this study is to test whether parasitic Hyalorbilia spp., isolated from sugarbeet cyst nematodes (Heterodera schachtii) in California, could also suppress soybean cyst nematodes (H. glycines). Three H. oviparasitica clade strains, DoUCR50, HsImV27, and ARF18-L, were cultured in powdered peat for use in greenhouse nematode suppression tests. Soils were amended with 500 CFU/cm³ of each fungal strain or autoclaved peat inoculum as a control, seeded with soybeans (Glycine max cv. Williams 82), and 3 weeks later, inoculated with 250 J2 of H. glycines. After 1,260 degree days, cysts and females were collected by flotation sieving and enumerated. DoUCR50, HsImV27, and ARF18-L reduced cysts and females of H. glycines by 73, 87, and 0%, respectively. Egg parasitism was tested by incubating eggs of H. schachtii and H. glycines on water agar cultures of DoUCR50 and HsImV27. Individual eggs of H. schachtii or H. glycines were parasitized by DoUCR50 at rates of 15 or 13%, respectively. Eggs placed in pairs were parasitized at 38 and 43%, while eggs placed in groups of four were parasitized at 70 and 63%, respectively. HsImV27 parasitized fewer than 10% of eggs of either nematode, regardless of egg group size. Both DoUCR50 and HsImV27 were observed to parasitize white females of H. glycines and H. schachtii in tissue culture.