A review of three major fungal diseases of Coffea arabica L. in the rainforests of Ethiopia and progress in breeding for resistance in Kenya

In a review of their own research the authors summarize incidences and distributions of the most important fungal diseases in Ethiopia and progress in breeding for resistance. Ethiopia, as the centre of origin for Coffea arabica, hosts a large diversity of germplasm. The incidences of diseases are based on observations in the montane rainforests of the southeast (Harenna) and southwest (Bonga, Berhane-Kontir, Yayu) of Ethiopia. Major diseases are Coffee Leaf Rust (CLR), Hemileia vastatrix; Coffee Berry Disease (CBD), Colletotrichum kahawae and Coffee Wilt Disease (CWD), Gibberella xylarioides (Fusarium xylarioides). CLR incidences in Ethiopia were present in all regions with highs between January and March and lows between June and October. CBD was present mostly in Bonga (40.0%) and Yayu (26.3%), but less frequent in Harenna (18.6%) and Berhane-Kontir (6.0%). CWD as a recently developed disease in Arabica coffee could be detected ranging from 2.4% in Berhane-Kontir to 16.9% in Yayu. CLR has been a serious constraint in all production countries since it became prominent in Ceylon in the late 19th century after leaf infection defoliation affects plants. CBD was first observed in Kenya in 1922. The disease is currently confined to the African continent in all countries that grow Arabica coffee. In the mid-1990s in the Democratic Republic of Congo, Uganda and Tanzania a resurgence of CWD in Robusta coffee and in Ethiopia in Arabica coffee occurred. Over the last 40 years breeding activities have been carried out to combat CLR, CBD and CWD. Breeding for resistance against CLR in Arabica coffee has successfully utilized single or combinations of major genes designated as SH genes. Major gene resistance has also been deployed in breeding for resistance against CBD, whereas in the case of CWD, selections of tolerant Arabica accessions are being pursued from local landraces in Ethiopia.