The Occurrence of Fusarial Wilt in Normally Resistant 'Dwarf Cavendish' Banana

In the Canary Islands, fusarial wilt caused by Fusarium oxysporum f. sp. cubense has destroyed areas of up to 1 hectare of normally highly resistant 'Dwarf Cavendish' bananas in some farms. Scattered isolated cases of wilt are more common than these acute attacks. Severe localized attacks have also been reported from Taiwan. Where scattered isolated plants are attacked in Gran Canaria, recovery from wilt often occurs in the following suckers. Pathogenicity tests with F. oxysporum f. cubense isolates from Dwarf Cavendish from Gran Canaria and Taiwan, other Cavendish varieties from Central America, and from the susceptible Gros Michel variety showed that all isolates are race 1 and a new race capable of attacking Cavendish varieties has not developed. The breakdown of resistance of Dwarf Cavendish in localized areas in Gran Canaria is attributed to adverse growing conditions; poor drainage and soil permeability appear to be the main contributing factors. Low seasonal temperatures and, in some areas, low soil pH and salinity may also contribute to reduced resistance to wilt. A certain combination of all factors contributing to adverse growth prevents the expression of the full genotypic resistance of the variety and wilt occurs.