Evaluation of released arabica coffee varieties (coffea arabica l) for major coffee diseases with especial emphasis to coffee wilt disease (Gibberella xylarioides) at jimma, Ethiopia

Abstract

Seedling inoculation test is important for rapid assessment of resistance of young coffee seedlings and may also be used for pre screening of large number of progenies for major coffee disease such as CBD and CWD. Seedlings of released coffee varieties were inoculated with C .kahawae and Gibberella xylarioides isolate   in the laboratory, where environmental conditions are best regulated. The result showed highly significant (p < 0.01) difference in CBD and CWD infection among released coffee varieties. The mean percent infection varies from 2.93 - 85.92% and 0.0-90 for CBD and CWD respectively.  Low disease severity levels were recorded on released coffee variety 741, 754 and 75227, 744 and Feyate, Odicha for CBD and CWD respectively. Higher CBD severities were recorded on coffee released variety 74165, 74148, 74140, 74110, 74112, 74158 and 7487 under laboratory condition however; no disease outbreak was reported under field condition as the varieties are field resistant. On the other hand except Feyate, Odicha, Catimor J-19 and Mechara-1 most pure line and all hybrids released coffee varieties exhibit susceptible reaction. In areas where there is enough CWD inoculums load pathogen and environmental condition is highly suitable Varieties which express susceptible reaction under laboratory also express susceptible reaction under field condition. Understanding the gene(s) that govern resistance to CWD and mode of inheritance mechanisms and large CWD screening program is of paramount importance to implement disease management options. More research work on biochemical and morphological defense mechanism which contributes to CBD resistant and Host defence mechanisms needs to be investigated.

Keywords: Released coffee varieties, Arabica Coffee, Seedling test, Coffee berry disease, Coffee wilt disease.