Targeting Meloidogyne incognita with Clonostachys rosea: Strain-Dependent Biocontrol Performance and Yield Effects Under Greenhouse Conditions.

The root-knot nematode Meloidogyne incognita poses a major challenge to global crop production, yet sustainable management options remain limited. We evaluated a collection of Clonostachys rosea isolates for their antagonistic potential using a stepwise approach that included in vitro assays, in planta tests, and greenhouse trials. Clear strain-dependent differences in biocontrol activity were observed across the different experimental stages. In vitro, several isolates strongly inhibited egg development and suppressed second-stage juvenile (J2) motility, with the magnitude of inhibition varying among isolates, concentrations, and incubation times. Changes in motility at some intermediate concentrations indicated that inhibition was not uniformly sustained over time. In cucumber assays, several isolates reduced root galling, with stronger suppression generally observed following J2 than egg inoculation. Selected isolates were subsequently evaluated under greenhouse conditions on tomato, where 1308, 1910, and 2084 produced reductions in root galling at selected early and mid-season assessments. Although differences in galling diminished under prolonged nematode pressure, selected isolates produced harvest-specific increases in individual fruit weight, whereas cumulative fruit number and fruit weight did not differ significantly among treatments. These results indicate that effective C. rosea isolates can contribute to integrated nematode management by reducing early nematode infection and potentially supporting plant performance, even when long-term nematode suppression is limited. Our findings emphasize the importance of multi-stage screening and targeted isolate selection to identify fungal antagonists with activity across different experimental conditions.