Ecophysiological characteristics of the nematophagous fungus, Plectosphaerella plurivora, with biocontrol potential on Nacobbus aberrans s.l. in tomato

Abstract

The plant-parasitic nematode, Nacobbus sp., is responsible for signi cant economic losses in horticultural production centers in Argentina and other countries in America, alone or in combination with other biotic and abiotic factors. Although the genus distribution is restricted to the American continent, it has quarantine importance and is subject to international legislation to prevent its spread to other regions. The management of phytoparasitic nematodes through biological control strategies is a promising eco-compatible alternative, allowing the sustainability of the crop horticultural system. Results of this study, rstly allowed ecophysiologically characterize Plectosphaerella plurivora SRA14, a strain with nematophagous activity on N. aberrans s.l. This fungal strain developed in vitro under a wide temperature range (20-30 °C), nevertheless the highest levels of water stress (Ψ: -7 and -10 Mpa; a W : 0.95 and 0.93) inhibited its growth. Notwithstanding, the production of extracellular enzymes by this strain was low, P. plurivora SRA14 was able to develop in the rhizosphere and endorhizosphere of the tomato and basil crops without affecting the plant vigor parameters and producing phytotoxicity signs. Secondly, this study evidenced the biocontrol activity of P. plurivora SRA14 on N. aberrans s.l. population in tomato implanted both on sterile (arti cially inoculated) and naturally infested soils via greenhouse pot experiments. The results of this work revealed for the rst time the potential of P. plurivora SRA14 to consolidate itself as a biological control agent of the phytoparasitic nematode, N. aberrans s.l., in horticultural crops.The population of N. aberrans s.l. (MH000315) isolated from a horticultural eld in Río Cuarto, Córdoba, Argentina, and identi ed by Sosa et al. (2018) was maintained in tomato plants (Solanum lycopersicum L. var. valouro) under greenhouse conditions. To obtain the inoculum, egg masses were extracted by dilaceration under a stereoscopic microscope from infested plant galls and placed in conical tubes with sterile distilled water. The obtained solution was homogenized and observed under an optical microscope to reach the necessary concentration of eggs. Fungal growth studiesThis test was carried out following the methodology proposed by Girardi et al., (2022). PDA plates were inoculated in the center with a 0.5 cm diameter disc of the fungus. The water activity (a W ) of the culture medium was modi ed by adding glycerol (0.99, 0.98, 0.95, and 0.93) and the matrix potential (Ψm) by PEG 8000 (-0.7, -3, -7 and − 10 MPa) (Dallyn and Fox, 1980). Plates with 0.99 a W were incubated at 20, 25, and 30°C for 15 days to evaluate the effect of temperature. Each treatment was performed in triplicate. Fungal growth was examined daily, evaluating the diameter of the fungal colonies to calculate the growth rate (Passone et al., 2005). Production of extracellular enzymes Semiquantitative studiesProtease, amylase, lipase, and chitinase activities were evaluated by plate technique using the same ...