ABSTRACT
Coconut (Cocos nucifera L.) production is affected by several factors; among them, diseases play a significant role. Botryodiplodia theobromae (Pat.) is the causative agent of coconut fruit rot and premature nut fall diseases, which lead to decreased yield. Understanding the factors that promote B. theobromae spread can help control the pathogen in coconut-growing areas. The study evaluated B. theobromae aiding coconut fruit rot and premature nut fall diseases in two major coconutgrowing locations in Ovia North-East Local Government Area, Benin City, Edo State. The study analyzed diseased coconut fruits in NIFOR Main Station and Coconut Garden, Isihor, using cultural and molecular approaches to identify the causal agents of fruit rot and premature nut fall diseases. The DNA concentration and purity were determined. The DNA was amplified with a polymerase chain reaction (PCR) using a universal primer (ITS1F/4R) and three specific primers (Lt347-F/R, Bt2aF/bR, and EF1-728F/EF2-728R). The PCR amplicons were fractionated using gel electrophoresis. The ITS1F/4R amplicons were sequenced and analyzed using bioinformatics and phylogenetic methods to identify the pathogen. The genetic similarity and variation of the pathogen were also determined. Data on fruit rot and early nut fall diseases in coconut were collected using simple random sampling, and the daily weather factor data in Ovia North-East Local Government Area was also collected. The study utilized regression analysis to analyze the impact of weather factors on the prevalence of fruit rot and early nut fall diseases in coconut. Botryodiplodin was detected in the pathogen using an in-culture technique that supplemented Czapek Dox agar (CDA) medium with glycine or sucrose with glycine agar medium. Findings from the study demonstrated that eight isolates of B. theobromae were identified by culture and molecular features as the cause of coconut fruit rot and premature nut fall diseases. The eight B. theobromae isolates, coded as Bt.NGD, Bt.NOD, Bt.NYD, Bt.NRD, Bt.IGD, Bt.IOD, Bt.IYD, and Bt.IRD, were grouped into five: Group 1 consists of 3 isolates (Bt.NYD, Bt.NGD, and Bt.IYD with accession number MW774360); Group 2 consists of 2 isolates (Bt.IGD and Bt.IRD with accession number OM617921); and Groups 3 to 5 consist of 1 isolate each (Bt.NOD, Bt.NRD, and Bt.IOD with accession numbers MW282879, MZ502166, and MZ496729, respectively). Group 1 isolates (37.5%) were more prevalent in both locations, followed by group 2 isolates (25%), and groups 3 to 5 (12%). Isolates Bt.IOD, Bt.IYD, and Bt.IRD exhibit high genetic distance at specific sites in their nucleotide sequence, while Bt.NGD, Bt.NOD, Bt.NYD, Bt.NRD, and Bt.IGD have low genetic distance. The NIFOR Main Station had a higher PDO of fruit rot and premature nut fall diseases of coconut than Coconut Garden, Isihor. Temperature, rainfall, and humidity significantly influence the PDO of fruit rot and premature nut fall diseases in coconut varieties across various locations, growing seasons, and sampling periods. The inculture technique of supplementing the CDA medium with glycine showed that only sucrose (among other medium components) promoted botryodiplodin detection by the chosen B. theobromae isolates. The findings from this study have provided a guide for proper identification of B. theobromae, that is a prerequisite for early diagnosis and management of this pathogen in coconut producing areas.
