Molecular Characterization of Phytophthora Pod Rot of Cocoa (Theobroma cacao L.) in Southwestern Nigeria

Background and Objective: Theobroma cacao L., is an important economic tree in Nigeria but is limited by Phytophthora pod rot (PPR).Efficient management of PPR requires identification and characterisation of the causal pathogen (CP).However, there is a dearth of information on the CP of PPR on the study site.Therefore, this study examined the characterization of PPR of cocoa in Southwestern Nigeria.Material and Methods: Fungal isolates were obtained from cocoa pods and pure cultures were assessed for pathogenicity following standard procedures.Morphological characteristics were determined by measuring the sporangial pedicel length (SPL), sporangial breath (SB), SPL: SB and the sporangial shape (SS) with the shape of the mycelial growth.The molecular analysis was carried out among PPR isolates and compared with CP genomes within the Phytophthora database.Data were analyzed using descriptive statistics and ANOVA at " 0.05 .Results: A total of 135 fungal isolates were identified and 45 were pathogenic in all the states.The mycelial growth of all isolates was cottony in appearance with a colony pattern slightly papillate.The SPL ranged from 29.9±7.89 to 38.8±8.65, while SB ranged from 24.01±5.42 to 30.8±5.35 and the SPL: BR was from 1.2±0.13 to 1.4±0.09.The SS was ellipsoid in all isolates.Thus, established the characteristic CP of PPR of cacao as Phytophthora megakarya.Extracted DNA and PCR amplification of the pathogen at ITS1 and ITS4 yielded an estimated 550 bp product.Conclusion: Results concluded that the Phytophthora megakarya is the causal organism of Phytophthora pod rot of cocoa in Southwestern Nigeria.