Location: Subtropical Horticulture Research
Project Number: 6038-21000-027-004-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Apr 1, 2025
End Date: Mar 31, 2030
Objective:
1. To standardize the design of experiments, including the instrumentation, protocols and genotypes tested around abiotic stress and root architecture characterization.
2. Screening of TARS germplasm collection to identify sources of favorable alleles, validation of phenotypes for a subset of traits linked to markers of large effect, conduct controlled crossing for development of multiparent mapping populations and trait stacking and duplication of material at both cooperator and ARS locations.
3. Development of improved and open pollinated populations of EET-400 for use as rootstock, planting of a field trial with 2 commercial scions on 3 populations of rootstock with 5 replicates in 3 blocks, single tree data collection on yield components (total pods, beans per pod, bean dry weight), vigor (base diameter, plant height), physiological traits to be determined as well as resistance to key pests and diseases (Lasiodiplodia spp, Phytophthora palmivora).
4. Increase production of cacao pods through maintenance of the USDA-TARS germplasm collection by tree rehabilitation and manual pollination.
5. Assess disease resistance across the USDA-TARS cacao germplasm collections by splitting phenotyping assays between both the USDA-Mayaguez and Mars-Davis IPM laboratories. Integrate phenotypic results on disease resistance and other desirable agricultural traits to identify superior cacao clones, facilitating informed breeding decisions.
6. Investigate the virus symptomology of Cacao Mild Mosaic Virus (CaMMV) in cacao, focusing on transmission vectors and symptom variability using Koch’s postulates. Screen for signs and symptoms of CaMMV and its vectors on a subset of cacao at USDA-TARS Mayaguez, Puerto Rico. Develop host-range tests of CaMMV and assess the distribution of the virus and its mealybug vectors across various farms in Puerto Rico
Approach:
Maintain, enhance and evaluate the germplasm collection of cacao and relatives maintained at Mayaguez, Puerto Rico and Hilo, Hawaii. Utilize the cacao germplasm to study root architecture and abiotic stress resistance, develop molecular markers for controlled crosses, and develop rootstocks and conduct cacao performance trials to evaluate newly released clones in farmers' fields in Hawaii and Puerto Rico.