Disease suppressiveness to Fusarium wilt of banana in an agroforestry system: Influence of soil characteristics and plant community

Abstract

One of the most destructive diseases of banana is Fusarium wilt or Panama disease, caused by the soilborne fungus Fusarium oxysporum f. sp. cubense (Foc). Foc is widespread in almost all banana-growing areas and cannot be effectively controlled by chemical or biological measures. Fusarium wilt could potentially be managed by the promotion of soil disease suppressiveness, but little is known how soils attain a higher level of disease suppression and how crop management can impact on this. Banana cultivar (cv.) Maçã, a cultivar highly susceptible to Foc race 1, was grown on a farm managed as agroforestry system in Pedra Dourada, Brazil, where Foc race 1 is present in soil. At some locations on the farm banana plants of cv. Maçã stayed productive, while on others it succumbed rapidly. We hypothesized that the differences in disease severity on the farm could be attributed to different levels of soil disease suppressiveness. In this study, we assessed the level of disease suppression of the different locations and elucidated potential factors that could promote disease suppression in soil. Patches with confirmed presence of Foc race 1 were sampled and tested for Fusarium wilt suppression in greenhouse assays. The plant community composition, soil abiotic properties and soil microbial community of the different locations were compared. Locations with a higher level of disease suppression were characterized by a low density of the susceptible cv. Maçã, a high diversity of other banana varieties, a higher clay content, higher pH and lower soil cover by graminoids. Banana cv. Ouro was only present in the three most suppressive patches. The results of this study suggest that in soils with favorable abiotic properties, a good plant arrangement, in which cv. Maçã is grown in mixed stands with other banana varieties, can help to promote Fusarium wilt suppression.