The vulnerability of bananas to globally emerging disease threats
Banana cultivation has increased significantly over the last century to meet the growing demand for this popular fruit. Originating in Southeast Asia, bananas are now produced in over 135 different countries in tropical and subtropical regions of the world. The vast majority of this expansion of production is based on a single banana variety ”Cavendish” which makes up almost all the export trade grown in large scale monocultures as well as a large part of the local trade and represents over 40% of all bananas grown globally. Over the last century several major diseases of the banana have emerged, and widely expanded their geographic ranges. Cultivars within the “Cavendish” variety are highly susceptible to these diseases including: Yellow Sigatoka, Black leaf streak, Eumusae leaf spot, Freckle, Fusarium wilt Tropical race 4, Banana bunchy top and the bacterial wilts Moko, Xanthomonas wilt and Banana blood disease. This review graphically illustrates the emergence and rapid intercontinental spread of these diseases and discusses several major disease epidemics in bananas. Evidently, the large-scale monoculture based on the single variety “Cavendish” has resulted in an extreme level of genetic vulnerability. The resistance to diversification in the Cavendish production chain and the lack of investment in genetics and plant breeding in the recent past means that currently limited genetic solutions are available to replace the Cavendish banana with a set of market acceptable resistant varieties utilising a range of different genetic backgrounds.