Abstract
The continued dispersal of Fusarium oxysporum f. sp. cubense Tropical race 4 (FocTR4), a quarantine soil-borne pathogen that kills banana, has placed this worldwide industry on alert and triggered enormous pressure on National Plant Protection (NPOs) agencies to limit new incursions. Accordingly, biosecurity plays an important role while long-term control strategies are developed. Aiming to strengthen the contingency response plan of Ecuador against FocTR4, a population biology study—including phylogenetics, mating type, vegetative compatibility group (VCG), and pathogenicity testing—was performed on isolates affecting local bananas, presumably associated with race 1 of F. oxysporum f. sp. cubense (Foc). Our results revealed that Foc populations in Ecuador comprise a single clonal lineage, associated with VCG0120. The lack of diversity observed in Foc populations is consistent with a single introduction event from which secondary outbreaks originated. The predominance of VCG0120, together with previous reports of its presence in Latin America countries, suggests this group as the main cause of the devastating Fusarium wilt epidemics that occurred in the 1950s associated to the demise of ‘Gros Michel’ bananas in the region. The isolates sampled from Ecuador caused disease in cultivars that are susceptible to races 1 and 2 under greenhouse experiments, although Fusarium wilt symptoms in the field were only found in ‘Gros Michel’. Isolates belonging to the same VCG0120 have historically caused disease on Cavendish cultivars in the subtropics. Overall, this study shows how Foc can be easily dispersed to other areas if restriction of contaminated materials is not well enforced. We highlight the need of major efforts on awareness and monitoring campaigns to analyze suspected cases and to contain potential first introduction events of FocTR4 in Ecuador.
Highlights
Bananas (Musa spp.), are widely cultivated in over 135 countries throughout tropical and subtropical regions and ranked as one of the most important crops in the world [1]
Fusarium wilt of banana (FWB) was present in all provinces from the coastal area of Ecuador surveyed, including Esmeraldas, Manabí, Guayas, Los Ríos, El Oro, Bolivar, and Santo Domingo (Figure 1)
This is the case for Foc Tropical race 4 (TR4) a pathogen that emerged in South East Asia and currently poses the biggest threat to all banana-producing countries, either for local consumption or export, as it kills a great diversity of banana cultivars and contaminates soil for decades [41]
Summary
Bananas (Musa spp.), are widely cultivated in over 135 countries throughout tropical and subtropical regions and ranked as one of the most important crops in the world [1] They represent an important source of calories with high nutritional value, contributing to an elevated intake of carbohydrates, fiber, vitamins, and minerals [2] in the diet of over 500 million people [3]. The export trade of bananas makes a large contribution to national economies of main exporting countries, such as Ecuador, where bananas and their derived products represent the second largest export commodity after petroleum [4] It should be noted only 3 of the 50 recognized subgroups of banana account for 75% of the current global production [7].
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