Arbuscular mycorrhizal inoculation for nematode-resistant cocoa seedlings

Overview

Venezuelan cocoa production has historically been recognized for its high quality, yet yields remain roughly 50% below the world average, largely due to poor agronomic management and pest pressure. Nematodes are among the most damaging phytopathogens affecting cocoa in nursery and field conditions, yet updated research on their incidence and management remains limited.

This solution proposes the inoculation of cocoa seedlings with Glomeromycota fungi during the nursery stage to establish arbuscular mycorrhizal associations. These symbioses are expected to strengthen seedlings by reducing or preventing nematode infestation in roots and by stimulating the expression of plant defense-related genes, including pathogenesis-related proteins (PRPs) and other genes involved in the biosynthesis of defensive compounds. The result is a more resilient cocoa plant with improved nutrition and natural protection against soil-borne pathogens.

Technical specifications

Core approach:

• Nursery-stage inoculation of cocoa seedlings with arbuscular mycorrhizal fungi from the phylum Glomeromycota
• Formation of arbuscular mycorrhizae in seedling roots prior to field transplantation
• Induction of pathogenesis-related protein (PRP) gene expression and related defense-compound biosynthesis pathways
• Improved plant nutrition and biotic stress tolerance, particularly against nematode infestation

Validation methodology:

• Field diagnosis of nematode incidence in cocoa seedlings at nurseries
• Isolation and morphological characterization of nematode species
• Multiplication of nematode inoculum for controlled greenhouse trials
• Reproduction of Glomeromycota fungi for greenhouse experimentation
• Greenhouse trial with cocoa genotypes under four treatments: Control (no microorganisms), Nematodes only (N), Mycorrhizae only (M), and Nematodes plus Mycorrhizae (N + M)
• Harvest at 3 to 4 months to assess mycorrhizal colonization, nematode populations in the rhizosphere, nematode gall formation, aerial and root dry biomass, and PRP gene expression
• Statistical data analysis and dissemination through final reports and peer-reviewed publications

Technology readiness level

This research is at an early-to-mid stage of development. The underlying biological mechanisms of arbuscular mycorrhizal protection in cocoa are supported by prior literature, including work by Fister et al. (2016) on PRP gene activation. However, specific evidence linking Glomeromycota inoculation to nematode resistance and PRP expression in cocoa remains scarce, which this project aims to address. The planned greenhouse trials represent a controlled validation step before potential field-scale recommendations for cocoa nurseries in Venezuela and similar tropical production regions.