Analyses of fungal communities from culture-dependent and -independent studies reveal novel mycobiomes associated with Globodera and Heterodera species

Plant-parasitic nematodes are important pathogens of agricultural crops. Of particular importance are cyst nematode species of Globodera and Heterodera which remain a major constraint to global production of crops such as potato, soybean, and wheat. Recent restrictions on the use of some synthetic nematicides has created an urgent need for alternative methods of controlling cyst nematodes. This project aimed to: (i) document fungi found associated cyst nematodes, (ii) determine if the fungi associated with cyst nematodes are dependent on growth conditions or nematode species, (iii) identify core mycobiomes for each of the eight cyst nematode species, (iv) identify the core mycobiome across all cyst nematode species studied, and (v) determine if the fungi associated with Globodera species are structured geographically. Sixty cyst nematode populations from eight species – Globodera sp., G. ellingtonae, G. pallida, G. rostochiensis, H. avenae, H. carotae, H. glycines, and H. schachtii – were collected from several geographic locations globally and screened for fungi using both culture-dependent and -independent methods. The core mycobiome was determined for each species. In total, 744 species of fungi were found associated with cyst nematodes. Fungal species shared across all cyst nematode species included Pochonia sp., Sporothrix sp., Neocosmospora solani, Exophiala equina, Mortierella sp., and Sarocladium kiliense. The core mycobiomes were conserved between cyst nematode species irrespective of their geographic origin. Cyst nematodes collected from the field or from greenhouse cultures also recruited similar core mycobiomes. These findings could be relevant when choosing fungi to evaluate as biocontrol agents against cyst nematodes.