In vitro compatibility of Brassicaceae extracts with nematophagous fungi and their effects against Nacobbus celatus.

Abstract

Nacobbus celatus sp. n. is one of the main root-knot nematodes in the field destined for horticultural production of the central region of Argentine due to its ability to infect several host plants. The lack of new and safe active ingredients against this nematode has restricted control alternatives for growers. Egg-parasitic fungi and biofumigation with brassicaceae have been considered as potential candidates for the development of bionematicides. Nematicidal effects of Brassica oleracea var. italica (broccoli) and Brassica oleracea var. capitata (cabbage) aqueous extracts (AEs) against second-stage juveniles (J2) of N. celatus were evaluated in vitro. Fisher LSD tests evidenced significant nematicidal (α = 0.05) effects of the two AEs tested, with LD₁₀₀ of 250 and 500 μL mL^-1 for broccoli and cabbage, respectively. Compatibility assays between AEs and five nematophagous fungi were performed on soil extract medium conditioned at 0.99 water activity and incubated at 30, 25 and 20 °C. Purpureocillium lilacinum SR14 was the fungal strain that showed compatibility at levels of spore viability, growth rate and conidia productions at LD₅₀ (125 μL mL^-1) and LD₂₅ (60 μL mL^-1) of broccoli aqueous extract (BAE) and enhanced the nematophagous effect. Moreover, phytotoxic studies revealed that 125 μL mL^-1 of BAE applied at the transplantation time could be safely used without affecting tomato culture. In conclusion, the integrated application of BAE with P. lilacinum SR14, which combines two action mechanisms, represents a promising integrated strategy to management phytoparasitic nematodes.