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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #426431
Research Project: Integrative Genomic and Biological Approaches to Detect and Manage Emerging Foreign Fungal and Oomycete Plant Pathogens

Location: Foreign Disease-Weed Science Research

Title: Evidence of graft incompatibility and rootstock scion interactions in cacao

Author
item DUVAL, ASHELY - Mars, Inc
item TEMPELEU, ALEXANDRA - Mars, Inc
item SCHMIDT, JENNIFER - Mars, Inc
item Puig, Alina
item KNOLLENBERG, BEN - Mars, Inc
item CHAPARRO, JOSE - Mars, Inc
item MOTAMAYOR, JUAN CARLOS - Mars, Inc

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/2025
Publication Date: 8/3/2025
Citation: Duval, A., Tempeleu, A., Schmidt, J., Puig, A.S., Knollenberg, B., Chaparro, J., Motamayor, J. 2025. Evidence of graft incompatibility and rootstock scion interactions in cacao. Horticulturae. https://doi.org/10.3390/horticulturae11080899.
DOI: https://doi.org/10.3390/horticulturae11080899

Interpretive Summary: Cacao seeds are the foundation of cocoa powder and butter, essential to the global confectionery industry. Breeding programs improve cacao varieties through grafting, where a scion—genetically identical to the original plant—is fused with a rootstock, ensuring traits like high yield and disease resistance. However, while scions are well studied, the role of rootstock in shaping plant health and productivity remains largely overlooked. This study examines rootstock-scion interactions, revealing that rootstock identity significantly affects graft compatibility, leaf nutrition, and disease resistance. It is the first to report genotype-specific graft incompatibilities in cacao, emphasizing the importance of selecting the right rootstock to optimize plant survival and growth. These findings are crucial for cacao breeders, farmers, and researchers seeking more resilient, sustainable crops to support the industry’s future.

Technical Abstract: Despite the economic importance of cacao (Theobroma cacao, L.) and the scale of its cultivation, there has been limited progress in the selection and breeding of rootstock cultivars for the crop, and knowledge of rootstock specific interactions on horticultural traits is lacking. A three year greenhouse study conducted on grafted cacao plants (Theobroma cacao L.) demonstrates differences in graft compatibility between cultivars and describe rootstock-scion interactions around nutrition, vigor, carbohydrate parti-tioning, and resistance to Black Pod (Phytophthora palmivora Butler). We provide the first report of genotype-specific graft incompatibilities in cacao, as well as rootstock mediated differences in survival, foliar nutrients, and disease resistance. Rootstock impacts on multiple traits had a strong effect in the first year after grafting but lost significance in the second and third years, demonstrating potential limitations of con-tainers on growth. Rootstocks demonstrated potential for improving nutrient use effi-ciency at the nursery, as well as limiting accumulation of metals and increasing toler-ances to Black Pod. In addition to validating the basis for a rootstock scion interac-tion around specific traits, this study provides insights for conducting greenhouse studies on cacao.