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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #400681
Research Project: Diagnostics and Biological Approaches for Management of Emerging Oomycete Plant Pathogens

Location: Foreign Disease-Weed Science Research

Title: Phyllosphere microbial diversity, specific taxa, and environmental conditions mediate within-cultivar resistance to Phytophthora palmivora in cacao

Author
item SCHMIDT, JENNIFER - MARS, INC.
item Puig, Alina
item PFEUFER, EMILY
item DUVAL, ASHLEY - MARS, INC.

Submitted to: mSphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2023
Publication Date: 8/21/2023
Citation: Schmidt, J.E., Puig, A.S., Pfeufer, E., Duval, A.E. 2023. Phyllosphere microbial diversity, specific taxa, and environmental conditions mediate within-cultivar resistance to Phytophthora palmivora in cacao. mSphere. https://doi.org/10.1128/msphere.00013-23.
DOI: https://doi.org/10.1128/msphere.00013-23

Interpretive Summary: Black pod rot disease is the most damaging disease of cacao trees, which are grown for chocolate production. Black pot rod affects cacao cultivars differently. Some cacao cultivars are not damaged by the disease, while others may experience significant yield losses. However, in some cases, even trees of the same cultivar may show different levels of disease symptoms, with pods on one tree developing large lesions, while pods on a different tree develop small, or no, lesions. Therefore, scientists studied two cacao trees of the same cultivar that have shown different levels of resistance to black pod rot. The research looked at whether the tree's leaf microbiome might influence whether disease symptoms are severe or mild. A total of 88 microbes were shown to be significantly different in the microbiomes of the two cacao trees. Differences included several microbes that are known for their roles as plant pathogens and biocontrol agents. Nine fungal microbes were correlated with increased disease symptom development. Results of this study improve the understanding of the conditions affecting host resistance to black pod rot. This will help scientists and farmers develop more effective strategies for long-term disease control.

Technical Abstract: Black pod rot disease is caused by several species of Phytophthora, with P. palmivora being the most common. It is the most economically significant disease of Theobroma cacao, the plant whose beans are the main ingredient in chocolate. Cacao cultivars have varying levels of resistance to P. palmivora, but variation has also been observed in disease levels among trees of the same cultivar. This study examined two trees of the same clone with differing levels of disease resistance to determine which characteristics of leaf microbial communities were associated with resistance. Microbial communities on the resistant tree had higher bacterial diversity but lower fungal diversity. Six bacterial and 82 fungal strains differed in relative abundance between the trees, including putative biocontrol agents and numerous fungal pathogens. Nine fungi were correlated with increased lesion development. Results of this study improve the understanding the conditions affecting host resistance to black pod rot and will help scientists and farmers develop effective long-term disease control.