DISTRIBUTION OF BANANA (Musaspp.) FUSARIUM WILT (Fusarium oxysporum f. sp. cubense)AND EVALUATION OF CULTIVARS AGAINST THE DISEASE IN GAMO ZONE, SOUTHERN ETHIOPIA

Abstract

Fusarium Wilt, caused by Fusarium oxysporumf.sp. cubense(Foc), is the most important disease of banana worldwide, causing severe yield losses in commercial and local banana cultivars, but there is limited practical research information about the epidemiology and relative importance of banana fusarium wilt, and robust management options in Gamo zone, southern Ethiopia. Thus, the study was conducted to (1) determine the distribution, importance and intensity of the disease epidemics in association with agro-ecological factors, and (2) evaluate commercial banana cultivars resistance reaction against the disease. A total of 90 farmer fields were surveyed in three major banana growing districts during 2019 and, pot experiment was conducted with seven commercial banana cultivars in a factorial arrangement of completely randomized design with three replications. The associations of disease incidence and severity with independent variables were analyzed in logistic regression model using SAS procedure of GENMOD. Observations of external leaf symptoms and internal rhizome discoloration were conducted to determine the response of cultivars evaluated using standard scales of leaf symptom index (LSI) and rhizome discoloration index (RDI). The incubation period, disease incidence, percent severity index and area under disease progress curve data were subjected to analysis of variance (ANOVA) using the SAS software version 9.2and means were compared using LSD test (α= 0.01). Results of the survey study indicated that Fusarium wilt incidence was widely distributed in all the three districts, regardless of agro ecological factors. The highest mean incidence (47.37%) and severity (46.31%) were recorded at Daramalo while the lowest incidence (20.75%) and severity (28.63%) were from Arba Minch Zuria district. Variables like Banana cultivars, age of plantations, weeding practice, and disease management methods were very highly significantly (p<0.0001) associated with both incidence and severity of the disease. Farms growing improved cultivars reduced mean incidence by 43.6% and severity by 30.1%, compared with farms growing local cultivars. Results from the regression analysis of the association of agro ecological factors with Fusarium wilt incidence implied the necessity of awareness creation to all stake holders regarding distribution, importance and possible management options. The result obtained from evaluation of cultivars showed that William and Grand Naine were categorized resistant but Poyo and Ducasse hybrid were susceptible and highly susceptible respectively but Butuzua, Giant Cavendish and Dwarf Cavendish were tolerant. In addition analysis of variance revealed that incubation period and severity ranged from 10-46 and 13.33 - 63.33% respectively. Therefore, the susceptible and highly susceptible verities can be replaced by the resistance ones to reduce the devastation posed by the disease and tolerant cultivars could be maintained in production with the implementation of effective integrated disease management practices.Fusarium oxysporum f.sp.cubense(Foc) variability and race identification and determination of crop rotation would be the future research directions.