Combining cyclic lipopeptides and cinnamon extract enhance antifungal activity against Fusarium oxysporum strains pathogenic to banana and delay Fusarium wilt under greenhouse conditions

Fusarium wilt of banana (FWB) caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc) is a widely distributed disease that generates devastating losses in banana production. Foc belongs to the Fusarium oxysporum species complex (FOSC) which includes several evolutionary lineages. Nine of them are pathogenic to banana such as F. phialophorum, F. grosmichelli, F. duoseptatum and the most aggressive F. odoratissimum tropical race 4 (TR4). No control method has been successfully implemented to manage FWB, then enhancing the potential of management approaches can avoid or delay disease epidemics and reduce disease severity. Here we determined the antifungal effect of different plant-based extracts against Foc in vitro, and whether the combination of cinnamon (Cinnamomum zeylanicum) extract and Bacillus tequilensis EA-CB0015 cyclic lipopeptides had an additive effect against different Foc lineages in vitro and against FWB in banana plants in greenhouse. We found, from 17 plant-based natural extracts, that cinnamon was highly active against Foc strain IB (race 1). Furthermore, cinnamon and cyclic lipopeptides inhibited different strains of various evolutionary lineages of Foc belonging to race 1 and TR4, and their combination increased in 1.4-fold the effect of the single extracts in vitro. Our results showed that soil concentration of F. odoratissimum TR4-II5 decreased by 1000-fold when treated with the combination of 488 mg L⁻¹ cinnamon and 128 mg L⁻¹ lipopeptides in a soil microcosm system after 5 days of incubation, followed by a partial population recovery after 21 days. In greenhouse experiments, the combination reduced external but not internal FWB symptoms, and cinnamon extract had a significant impact on internal plant symptoms. Taken together, the effect of cyclic lipopeptides with cinnamon extract on Foc supports their function towards delaying the effect of disease progression and suggests that the combination enhances the effect of the single extracts.