Study of Okra Leaf Curl Disease and Its Whitefly Vector (Bemisia Tabaci) Vector in Three Agro-Ecological Zones in The Volta and Oti Regions of Ghana

Abstract

Research was carried out on okra leaf curl disease (OLCD) and its whitefly vector in the three agro-ecological zones of the Volta and Oti regions. The study evaluated the prevalence and severity of the disease, the level of the whitefly population and the impact of weather variables on their abundance. In order to evaluate the prevalence of the disease, farmers’ knowledge of leaf curl disease, agronomic methods, and use of pesticides to manage pest and disease outbreaks, questionnaires were administered. The study also assessed quantitatively the intensity (severity and incidence) of the disease. The study then examined the resistance levels of 21 okra varieties to the disease and its vector during the major and minor okra seasons and further examined the molecular diversity of the Begomoviruses responsible for okra leaf curl disease. The majority of farmers observed whitefly and Okra leaf curl disease on their farms during both minor and major seasons. The mean incidence of the disease ranged from 69.69% to 80.62%, with a mean severity index of 1.18 to 1.44. The mean disease incidence was higher in coastal with 77.42%, than in transition (72.56%) and forest (71.85%) zones in both year one and two. Generally, the minor season had a much higher level of significance of disease incidence than the major season. A total 38,504 whiteflies were estimated where 25,978 for minor season and 12,526 in the major season. Varieties Kobinami, 1097, and 2033 were the most susceptible varieties to okra leaf curl disease. PCR using degenerate primers detected the presence of Begomoviruses. Sequence analysis of the PCR products revealed the presence of Okra yellow crinkle virus (OYCrV), which is responsible for okra leaf curl disease in the Volta and Oti regions. This is the first report of Okra yellow crinkle virus (OYCrV) in Ghana.