In Uganda, Coffee is a major export crop with robusta coffee forming the greater bulk of the coffee export, However, production is constrained by coffee wilt disease (tracheomycosis) caused by Fusarium xylarioides Steyaert. The disease was first reported in 1993 and since then it was spread rapidly covering all traditional robusta coffee growing areas in the relatively short period of time. This study was conducted to establish the role of alternative hosts and infected robusta coffee planting materials in transmission of tracheomycosis and the susceptibility of robusta coffee varieties to tracheomycosis. Six commercial varieties were evaluated under screen house conditions to assess their susceptibility to tracheomycosis. Seedlings, seeds and cuttings were used to study the transmission of tracheomycosis through planting materials. In addition, four hundred plant samples were collected from different robusta coffee growing areas to establish the host range of Fusarium xylarioides Steyaert. Results indicated that all the types of infected planting materials transmitted coffee wilt disease to healthy seedlings. This shows that, as long as infected planting materials are used to raise robusta coffee, tracheomycosis transmission although at varying levels indicating susceptibility. Except robusta coffee materials, Fusarium xylarioides teyaert was not isolated form any of te suspected alternative host plant samples collected form the immediate vanity of diseased coffee plants but several Fusarium species were isolated including; F. moniliforme, F. semitectum (now F. pallidoroseum), F equiseti, F. avenaceum, F. solani, F. graminearum, F. acuminatum, F. oxysporum, F. demerum, F. sambunaceum and F. udum. The study results indicated that infected seeds, seedlings or cuttings transmit coffee wilt disease. All the commercial varieties showed symptoms of tracheomycosis and eventually died. The varieties showed almost the same level of susceptibility to tracheomycosis infection, although 258/24(0) consistently showed the lowest response and 1s/6 and 1s/2 showed high tracheomycosis incidence. This indicates that all the improved varieties were susceptible to tracheomycosis. The failure to isolate alternative hosts from all the samples collected indicates that Fxylarioides has relatively few alternative hosts. Hence, more effort should be directed to controlling the disease using host plant resistance of coffee plant. It is suggested that development and use of more resistant coffee varieties and the use of exclusive local quarantine should be strengthened in order to contain the disease.
Date of publication:
RUFORUM Theses and Dissertations
Agris Subject Categories:
Prof. Adipala Ekwamu (Executive Secretary of RUFORUM), Dr. Africano Kangire ( Coffee Research Institute, NARO)