Exploring Fungal-Nematode Interactions in Disease Complexes

Multiple disease complexes include plant pathogenic fungi and plant parasitic nematodes ( Back et al. 2002 ), including Verticillium dahliae with Pratylenchus nematodes in wilt disease of mint ( Wheeler et al. 2019 ), Rhizoctonia solani and Ditylenchus dipsaci in sugar beet crown and root rot ( Hillnhütter et al. 2011 ), and Fusarium solani and Meloidogyne incognita in root rot of lentil ( Ahmed and Shahab 2018 ). Similarly, it has been suggested that soybean sudden death syndrome (SDS) is a disease complex composed of F. virguliforme and SCN, where SCN increases SDS synergistically with F. virguliforme ( Roth et al. 2019; Xing and Westphal 2013 ). Similarly, Macrophomina phaseolina, the causal agent of charcoal rot in soybean, is commonly found in the same fields as SCN and have a significant interaction on soybean yield ( Lopez-Nicora et al. 2020).

However, the exact role of SCN in these disease complexes in soybean remain unknown. Some hypotheses include nematodes vectoring fungi into plants, nematodes creating wounds that are easier for fungi to colonize, and altering defense gene expression that benefits fungal invasion. Using fluorescently labelled strains of fungi and time-course microscopy, we are investigating the way fungi and nematodes interact outside of a plant host. Further experiments include the plant host will also help elucidate how pathogen interactions affect plant disease severity.