Fusarium Wilt of Bananas in Jamaica: II. Some Apsects of Host-parasite Relationships

The incidence of Fusarium wilt in a given variety of bananais determined by numerous interacting factors such as geneticallydetermined resistance, physical and chemical soil conditions,and abundance of Fusarium oxysporum f. cubense. To attain markedresistance to wilt, ‘Gros Michel’ apparently requiresa combination of conditions; thus the soil must be alkaline,of medium to heavy texture, and rich in available potash. Nitrogenfertilizing tends to increase susceptibility to wilt. Some striking effects of weather on wilt incidence are describedand various aspects of crop management are discussed: soil deteriorationunder bananas undoubtedly contributed to development of wiltin the past. In the earliest stages of rootlet infection, the pathogen growsmore slowly in the resistant ‘Cavendish’ than inthe susceptible ‘Gros Michel’, probably owing tomore effective tissue reactions in the former. In the field,infections progressing along the root are often checked at theroot base: with ‘Gros Michel’, however, a smallproportion enter the rhizome and as a result wilt generallydevelops. Ability to check such infections, leading to recovery,is only exhibited on very fertile soils. The possible mode of action of various factors on wilt incidenceis discussed, and the importance of vigorous root growth inpromoting host resistance is emphasized.