Enzymatic and proteomic changes in resistant and susceptible cacao clones cultivars reveal distinct response mechanisms to Phytophthora citrophthora infection

Angra Paula Bomfim Rego¹Irma Yuliana Mora Ocampo¹Elza Thaynara Cardoso De Menezes Assis¹Márcia Christina da Silva Branco¹Edna Dora Martins Newman Luz^1,2Carlos Priminho Pirovani³Ronan Xavier Corrêa^3*

• ¹Universidade Estadual de Santa Cruz, Programa de Pós-Graduação em Genética e Biologia Molecular, ilhéus, Brazil
• ²Comissao Executiva do Plano da Lavoura Cacaueira, Brasília, Brazil
• ³Universidade Estadual de Santa Cruz Departamento de Ciencias Biologicas, Ilhéus, Brazil

Black pod rot, caused by Phytophthora species, is one of the most severe diseases affecting cocoa production. Among these species, P. citrophthora is considered one of the most aggressive, yet little is known about the molecular responses of cocoa to this pathogen. This study aimed to investigate the defense mechanisms of cacao against P. citrophthora through Formatted: Font: Italic enzymatic analyses and gel-free comparative proteomics. Seedlings obtained by rooting cuttingsLeaves from a one resistant clone (PH 16) and a one susceptible clone (SJ 02) cultivar were inoculated with the pathogen, while controls received sterile distilled water. The activities of ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), and superoxide dismutase (SOD) were measured at 6, 12, 18, and 24 hours after inoculation (HAI). Protein abundance was evaluated at 24 HAI using mass spectrometry. The pathogen induced GPX activity from 6 HAI in the resistant clone and from 12 HAI in the susceptible clonecultivar, while APX activity increased in both clonecultivars after 18 HAI. A total of 1,583 proteins were identified across treatments. In the resistant clonecultivar, infection was associated with reduced photosynthesis, redirection of carbohydrate metabolism, and changes in the ascorbate/dehydroascorbate ratio, suggesting an efficient activation of defense responses. Constitutively abundant proteins related to antioxidant activity may also have contributed to resistance. In contrast, the susceptible clonecultivar showed limited protein abundance changes, with indications of increased metabolism of small molecules and accumulation of methylglyoxal, a cytotoxic compound linked to disease susceptibility. Overall, the results demonstrate that the resistant clonecultivar mobilizes early antioxidant defenses and metabolic reprogramming to cope with infection, whereas the susceptible clone exhibits inefficient responses leading to cellular damage. These findings provide new insights into cacao–-P. citrophthora interactions, offer a foundation for future transcription-level studies, and may support the development of new pre-breeding stages strategies for developing resistant cacao varietiescultivars.