Sustainable Cacao Production in Hawai‘i Through Clonal Rootstock Evaluation and Adoption

Commodities

• Agronomic: other
• Fruits: other
• Additional Plants: other

Practices

• Crop Production: varieties and cultivars
• Education and Training: farmer to farmer
• Pest Management: genetic resistance

Hawaiʻi's cacao and chocolate industry is expanding rapidly, fueled by strong demand for locally produced specialty chocolate, agritourism opportunities, and the unique status of Hawaiʻi as the only U.S. region producing commercial cacao. However, the industry is constrained by a critical and well-recognized agronomic gap: the absence of reliable, high-performing clonal cacao rootstocks. Although grower-led trials have identified elite scion varieties, the root system-responsible for water and nutrient uptake, anchorage, disease tolerance, and the physiological foundation of vigor and yield-remains largely unoptimized. Nearly all growers rely on seedling rootstocks, which are genetically variable and deliver inconsistent orchard performance, resulting in uneven vigor, unpredictable yields, susceptibility to disease, reduced nutrient efficiency, and poor establishment in marginal soils.

This project directly addresses that gap by evaluating promising clonal rootstocks across four independent producer farms on three islands (Oʻahu, Hawaiʻi Island, and Kauaʻi), combined with rigorous nursery trials and a coordinated statewide extension effort. The project integrates growers, researchers, and educators to produce actionable recommendations that support a more sustainable, profitable, and resilient cacao industry in Hawaiʻi.

Research Objectives (R1-R6)

1. Compare the agronomic performance of HSCT-4 and HSCT-5 clonal cacao rootstocks with their seedling progeny families and a pure-line seedling control.
2. Evaluate field performance across four contrasting agroecosystems on Oʻahu, Hawaiʻi Island, and Kauaʻi.
3. Conduct controlled nursery trials assessing graft success, early vigor, root architecture, cadmium uptake, and Phytophthora palmivora susceptibility.
4. Assess whether rootstock genotype influences final flavor quality using Cacao of Excellence (COE) standards.
5. Identify genotype × environment interactions for traits important to Hawaiʻi cacao.
6. Compare local Hawaiian rootstocks to international reference clones (EET-400, IMC-67)

Educational Objectives (E1-E3)

The educational plan aims to:

1. Increase grower and industry understanding of how clonal rootstocks influence vigor, yield, disease tolerance, cadmium uptake, and final flavor.
2. Provide hands-on training in propagation, grafting, orchard evaluation, and sustainable management.
3. Equip beginning farmers, agricultural students, and nursery professionals with practical skills for tropical orchard crops, using cacao as a model system.