Fungal peptidogalactomann as a biocontrol agent Against Meloidogyne incognita in cotton.

Root-knot nematodes (Meloidogyne incognita) severely limit cotton (Gossypium spp.) productivity, with conventional control methods facing ecological and efficacy challenges. Here, we evaluate a fungal peptidogalactomann (pGM), derived from Cladosporium herbarum (commercially formulated as Hariman), as a novel biocontrol agent that primes plant defenses against nematode infection. Under greenhouse conditions, foliar application of pGM at 100 μg·mL⁻¹ resulted in an 83% reduction gall formation compared to untreated controls and yielded a four-fold increase in resistant plants (gall index = 1.5 vs. 3.2 in controls; *p* < 0.01). Nematode egg production was reduced by 60% at 120 days post-inoculation. pGM triggered a biphasic defense response, evidenced by a remarkable 40,000-fold upregulation of the systemic acquired resistance gene PR1 and transient activation of phenylpropanoid (PAL) and jasmonate (LOX2) pathways. Notably, pGM supported healthy plant growth without phytotoxicity, contrasting with the phytotoxicity often associated with chemical nematicides. These findings indicate that pGM has strong potential as a sustainable alternative for M. incognita management in cotton, primarily by enhancing host immunity rather than exerting direct nematode toxicity. Further field trials are necessary to validate its effectiveness and to evaluate its integration into integrated pest management strategies.