Biological control potential of nematophagous fungi, Cladosporium and Plectosphaerella, against Meloidogyne javanica infecting eggplant

Meloidogyne javanica is one of the most devastating plant pathogens in Saudi Arabia. It is found in all cultivated vegetable growing areas in Saudi Arabia. According to Saudi Vision 2030, Saudi Arabia aims to increase organic farming by reducing reliance on pesticides. Thus, biological control using bioagents is considered the best choice due to Saudi Arabia’s land containing a high variety of bioagents. In this study, two strains of nematophagous fungi were isolated from root-knot nematodes (RKNs). Both strains were identified based on morphological characteristics, and the ITS rDNA region was amplified using ITS4 and ITS5 primer pairs. Data revealed that strain EF1, isolated from RKN females infecting eggplant, was identified as Cladosporium limoniforme (PP731792), and strain TJ5, isolated from second-stage juveniles (J2s) of RKN infecting tomato plants, was identified as Plectosphaerella cucumerina (PP731782). In vitro , parasitism tests of strains against J2s and egg hatching of RKNs showed that fungal strains significantly reduced egg hatching and increased mortality (%) of J2s compared to the control. Additionally, fungal culture filtrates (at concentrations of 50% and 75%) inhibited egg hatching by more than 95% and increased J2s mortality by more than 50%. In the pathogenicity test, EF1 and TJ5 showed no negative effects on eggplant seed germination, with 90% and 70% germination, respectively, compared with the control (90%). Under greenhouse conditions, C. limoniforme and P. cucumerina notably reduced M. javanica reproduction and root galling by more than 50%. Both strains stimulated plant growth; C. limoniforme and P. cucumerina increased dry shoot weight by 13.9% and 4.9% in healthy plants and by 34% and 9.2% in infected plants, respectively. Also, C. limoniforme and P. cucumerina increased root weight in infected plants by 26.2% and 3.7%, respectively. Thus, C . limoniforme and P. cucumerina were isolated for the first time from RKNs in Saudi Arabia. These strains show promising potential as biological control agents and plant growth-promoting fungi. The research highlights the potential of beneficial fungi as key components in integrated pest management for nematodes. Field trial studies should be designed to evaluate the efficacy of both strains against plant-parasitic nematodes.