Location: Subtropical Horticulture Research
Project Number: 6038-21000-027-000-D
Project Type: In-House Appropriated
Start Date: Jun 21, 2023
End Date: Jun 20, 2028
Objective:
1: Breed and release novel cacao germplasm and cultivars with superior yield, host-plant resistance to diseases, and/or tolerance to drought and elevated temperatures.
2: Conduct research to identify genetic markers and develop integrated genetic maps to support cacao breeding for resistance to biotic stresses and tolerance of environmental extremes.
2.A: Identify association between SNP markers and resistance or tolerance to Badnaviruses, Poleroviruses, Lasiodiplodia spp. Colletotrichum spp., Diaporthe spp and Neofusicoccum parvum in cacao germplasm.
2.B: QTL discovery for resistance to BPR in six full sib families containing two different sources of resistance and gene identification.
Approach:
Currently, the major losses in cacao are due to black pod rot (BPR), caused by several different Phytophthora species of which P. palmivora is the most common, frosty pod rot (FPR), caused by Moniliophthora roreri, and witches’ broom (WB), caused by Moniliophthora perniciosa. In addition, other emergent pathogens (Lasiodiplodia spp. Colletotrichum spp., Diaporthe spp and Neofusicoccum parvum) that in the past have been considered of minor importance have started to influence cacao production worldwide. Also, viruses (Badnaviruses and Poleroviruses) have been recently reported affecting cacao production in the Americas. Therefore, screening protocols for selecting germplasm resistance to these pathogens will be conducted by this project in the cacao germplasm accessions and in segregating populations at the USDA-ARS-TARS in Mayaguez, Puerto Rico since sources of resistance must be found. Even though, FPR, and WB are currently not found in Puerto Rico and Hawaii. Nonetheless, this project will conduct a preemptive breeding strategy based on evaluating cacao segregating populations developed in Puerto Rico for host-plant resistance in countries where those diseases are present to develop disease-resistant varieties before these diseases arrive in Hawaii and Puerto Rico. Several cacao accessions have been sequenced and their genome information is available. Single Nucleotide Polymorphisms (SNPs) markers have been developed using this sequence information and will be used to genotype cacao accessions and segregating populations previously screened for resistance to these diseases. Associations between SNP markers and gene for disease resistance will be pursued during this project. Since Cacao breeding is a slow process, due to the tree’s long reproductive cycle. Generated genotypic and phenotypic information will be used in combination to identify Quantitative trait loci (QTL) associate with target traits using genome-wide selection (GWS) methodology as well as genomic selection models to strengthen the effectiveness of the selection process and accelerate the development of disease resistant cultivars. This research effort deliver cacao improve germplasm and save the livelihood of thousands of small farmers in the Americas.
