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Biological control is a promising approach to reduce plant diseases caused by nematodes to ensure high productivity in agricultural production. Large‐scale analyses of genetic variation in fungal species used for biocontrol can generate knowledge regarding interaction mechanisms that can improve efficacy of biocontrol applications. In this study, we performed a genome‐wide association study (GWAS) for in vitro antagonism against the root lesion nematode Pratylenchus penetrans in 53 previously genome re‐sequenced strains of the biocontrol fungus Clonostachys rosea. Nematode mortality in C. rosea potato dextrose broth (PDB) culture filtrates was highly variable and showed continuous variation (p <.001) between strains, indicating a polygenic inheritance. Twenty‐one strains produced culture filtrates with higher (p ≤.05) nematode mortality compared with the PDB control treatment, while ten strains lowered (p ≤.05) the mortality. The difference in in vitro antagonism against P. penetrans correlated with antagonism against the soybean cyst nematode Heterodera glycines, indicating lack of host specificity in C. rosea. An empirical Bayesian multiple hypothesis testing approach identified 279 single nucleotide polymorphism markers significantly (local false sign rate < 10–10) associated with the trait. Genes present in the genomic regions associated with nematicidal activity included several membrane transporters, a chitinase and genes encoding proteins predicted to biosynthesize secondary metabolites. Gene deletion strains of the predicted nonribosomal peptide synthetase genes nps4 and nps5 were generated and showed increased (p ≤.001) fungal growth and conidiation rates compared to the wild type. Deletion strains also exhibited reduced (p <.001) nematicidal activity and reduced (p ≤.05) biocontrol efficacy against nematode root disease and against fusarium foot rot on wheat. In summary, we show that the GWAS approach can be used to identify biocontrol factors in C. rosea, specifically the putative nonribosomal peptide synthetases NPS4 and NPS5. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode (SCN) is the most important pest on soybean, a major crop worldwide. The SCN is considered both parasitic and pathogenic as it derives nutrition from the host and manipulates host physiology to do so. Currently, there are no commercially available chemicals that are specific, environmentally safe and cost effective to control SCN levels. Crop rotation, use of host resistance and other cultural practices remain the main management strategies. The need for bioprospecting other methods of controlling SCN is paramount, and fungi show promise in that respect. Several studies have evaluated fungi and fungal products as biocontrol options against plant-parasitic nematodes. This review discusses fungal genera isolated from the SCN with potential for use as biocontrol agents and the effects of their secondary metabolites on various stages of SCN development. The review also summarizes efforts to control SCN using soil amendments that could potentially impact fungal communities in the soil. [ABSTRACT FROM AUTHOR]

The soybean cyst nematode ( Heterodera glycines ) is a plant parasitic nematode that is a major plant pest worldwide and causes severe economic and yield losses. Piriformospora indica , a plant growth promoting fungus isolated from the Thar Deserts of western India, has been shown to protect a wide range of plants from various biotic and abiotic stresses. To evaluate the potential of P. indica to protect soybean ( Glycine max ) seedlings from damage by the soybean cyst nematode (SCN), we amended soil with two different concentrations of P. indica (2.5% and 5% w/w) and inoculated with second-stage juveniles (J2s) of SCN in each treatment. After 60 days, abundance of nematode eggs was measured by calculating SCN egg population densities. We found that egg density/100 cc soil was significantly decreased by 29.7% and 36.7% respectively in the soil amended with 2.5% and 5% P. indica compared to a control. Amendment with P. indica also had a strong growth and yield promoting effect in Soybean. Although root biomass was significantly decreased by 27.9% and 33.5% in the two treatments compared to the control, shoot biomass (dry weight) increased by 30.8% and 8.2% in the 2.5% and 5% P. indica treatments compared to the control. Additionally, plant development was accelerated and a 75% increase in flowering was observed between the 2.5% P. indica treatment and the control. We conclude that P. indica used as a soil amendment decreases abundance of the SCN in soil and has plant-growth promoting properties that may help offset yield losses due to plant parasitic nematodes. [ABSTRACT FROM AUTHOR]