Characterization and Effect of a Nematophagous Fungus Talaromyces cystophila sp. nov. for the Biological Control of Corn Cyst Nematode

The dynamic of plant-parasitic nematode populations in soil is closely related to soil microorganisms. Fungi from Heterodera zeae cysts were isolated to explore the decline phenomenon of the H. zeae population in the soil. Phylogenetic study of partial ITS, BenA, CaM, and RPB2 gene sequences, in addition to morphological investigations, were utilized to identify a nematode-destroying fungus. The nematicidal activity of a novel strain GX1 against H. zeae was assessed in vitro and in the greenhouse. Our findings revealed that strain GX1 is a new species of Talaromyces, named Talaromyces cystophila. It has a strong parasitic and lethal effect on H. zeae cysts, with 91.11% parasitism on cysts at 3 d after treatment. The contents of second-stage juveniles (J2s) and eggs inside the cysts were degraded, formed dense vacuoles, and the damaged eggs couldn't hatch normally. The spore suspension exhibited high nematophagous activity against nematodes, and fermentation filtrate exhibited marked inhibition of egg hatching and nematicidal activities on J2s. The hatching inhibition rates of eggs exposed to 1 × 108 cfu/ml spore suspensions or 20% 1-week fermentation filtrate (1-WF) for 15 d were 98.56% and 100%, respectively. The mortality of J2s exposed to 1 × 108 cfu/ml spore suspension reached 100% at 24 h; exposure to 50% 2-WF was 98.65% and 100% at 24 h and 48 h, respectively. Greenhouse experiments revealed that the spore suspension and fermentation broth considerably decreased H. zeae reproduction by 56.17%-78.76%. Talaromyces cystophila is a potential biocontrol strain with nematophagous and nematicidal activity.