Evaluating the efficacy of Arbuscular Mycorrhizal Fungi in mitigating Meloidogyne enterolobii infection in guava (Psidium guajava)

Meloidogyne enterolobii, widely known as the guava root-knot nematode, poses a growing challenge to global agriculture because of its broad host spectrum and capacity to bypass resistance genes in various crops. The present study focuses on assessing the ability of Arbuscular mycorrhizal fungi (AMF) to induce resistance against root-knot nematodes as an alternative to chemicals. Two AMF isolates, Glomus mosseae and Rhizophagus irregularis, isolated from the guava rhizosphere, were evaluated for their bio-efficacy against M. enterolobii. In vitro twin-chamber assays and root-exudate studies showed that Glomus mosseae enabled a nematode reduction of 85.5% in juvenile penetration and 91.2% in egg hatching in comparison with non-mycorrhizal controls. GC-MS analysis of root exudates from AMF-inoculated and control plants identified octadecanoic acid, heptacosane, acetic acid, and 2,4-di-tert-butylphenol in R. irregularis-inoculated plants, and dodecyl acrylate, acetic acid, and trilinolein in G. mosseae-inoculated plants. Pot experiment revealed that G. mosseae significantly enhanced growth parameters, including shoot length (59.4 cm), shoot weight (33.7 g), root length (32.5 cm), and root weight (11.78 g), in comparison to the control plants. The combined application of G. mosseae and R. irregularis significantly enhanced soil and plant health, increasing spore counts (285 per 50 g soil), mycorrhizal colonization (95%), dehydrogenase enzyme activity (61.2 nmol TPF g-1 h-1), and glomalin-related soil proteins (1.21 mg glomalin/g soil). Additionally, this treatment markedly reduced M. enterolobii infection in guava, with fewer galls (6.3) and egg masses (0.92 per 5 g root), highlighting its potential as an effective biocontrol strategy for guava cultivation.