Current state of Fusarium wilt of banana in the subtropics

Subtropically grown bananas have different interactions with Fusarium oxysporum f. sp. cubense (Foc), causal agent of Fusarium wilt of banana (FWB), when compared with those grown in the tropics. The designation ‘subtropical’ race 4 (SR4) was assigned to Foc strains able to infect Cavendish (AAA) cultivars in the subtropics, but not in the tropics. ‘Tropical’ race 4 (TR4) gained prominence with the appearance and spread of a Foc strain that severely affects Cavendish bananas in both the tropics and subtropics. Recent surveys in Asia revealed TR4 as the predominant strain both in the tropics and subtropics, affecting not only Cavendish, but also many other cultivars. In many subtropical banana zones, Foc races 1 and 2, which complete the racial structure of Foc, are also found and cause severe losses in certain market-preferred dessert bananas. Environmental constraints increase the susceptibility of Cavendish bananas to SR4. However, the role of abiotic stresses in cultivar susceptibility to Foc needs to be better understood. It is not clear why some Foc strains only affect Cavendish in the subtropics, and what other factors, including pathogen virulence and microbial functional diversity, might be driving disease epidemics. Field experience suggests that optimum soil and water management strategies can reduce disease intensity, but targeted studies are needed to understand the virulence of different strains, the impact of fluctuating temperatures, soil pH, organic matter breakdown and soil microbial dynamics. Research findings on the epidemiology and management of FWB in Australia, Brazil, China, India and South Africa are discussed to propose priority areas for the development of improved disease management practices. © 2020 International Society for Horticultural Science. All rights reserved.