Biocontrol Potential of Aspergillus oryzae against the Root-knot Nematode Meloidogyne javanica in Carrot (Daucus carota L.)

Abstract

Background: Carrot (Daucus carota L.) is an economically and nutritionally important vegetable crop severely affected by root-knot nematodes, particularly Meloidogyne javanica. This study evaluated the biocontrol potential and plant growth-promoting effects of Aspergillus oryzae against M. javanica in carrot. Methods: M. javanica was isolated from infected carrot roots and identified based on perineal-pattern morphology and molecular characterization. A. oryzae, isolated from the rhizosphere of healthy carrot plants, was identified using cultural, microscopic, and molecular characteristics. It’s in vitro nematicidal activity was evaluated based on egg-hatching inhibition and J2 mortality. Greenhouse experiments assessed the effects of different M. javanica inoculum levels and amounts of A. oryzae fresh mycelial biomass on plant growth, biochemical responses, and nematode-related parameters.
Results: Inoculation with 2000 J2 caused the greatest reduction in plant growth and photosynthetic pigments, whereas phenolic and proline contents and antioxidant enzyme activities increased. A. oryzae significantly inhibited egg hatching and increased J2 mortality in a concentration- and time-dependent manner. Among the combined treatments, T11 (2000 J2 + 2.0 g A. oryzae fresh mycelial biomass suspended in 10 mL DW) produced the greatest improvement in plant growth, photosynthetic pigments, and biochemical responses, whereas T12 (2000 J2 + 3.0 g A. oryzae fresh mycelial biomass suspended in 10 mL DW) showed the greatest suppression of gall formation, egg masses, soil nematode population, and reproduction factor.
Conclusion: A. oryzae showed plant-growth-promoting effects and nematode-suppressive activity and may serve as a promising component of sustainable M. javanica management in carrot. Further field validation and mechanistic studies are required to establish its efficacy, consistency, and mode of action.