Polydimethylsiloxane-polymethacrylate block copolymers containing quaternary ammonium salts against Fusarium oxysporum f. sp. cubense race 4 in soil: Antifungal activities and pot experiments

Abstract Fusarium oxysporum f. sp. cubense race 4 (Foc4) has significant impacts on banana production. Foc4 conidia can survive for many years in the soil, making control difficult. Thus, the inhibition of the conidia that serve as a continual source of inoculum in soil should be an effective way to control banana Fusarium wilt. In this paper, we first investigated the activities of polydimethylsiloxane-polymethacrylate block copolymers containing quaternary ammonium salts (PDMS-b-QPDMAEMA, labeled SixQ5) against Foc4 with microbroth dilution and toxicity plate assays. Then, the environmental behavior of these compounds, i.e., their adsorption and migration in soils, was further studied. Later, the effect and duration of SixQ5 on Foc4 in soil and the effects of SixQ5 on soil microbial diversity were evaluated. In addition, we conducted pot experiments to study the effect of Si5Q5 on banana Fusarium wilt. The results showed that SixQ5 showed a good inhibitory effect on Foc4, was easily adsorbed by the soil and was relatively immobile in soil. The inhibitory effect of SixQ5 on Foc4 was maintained for 30 d under continual inoculation of Foc4 into the soil (Foc4 addition every 2 d), and SixQ5 remained active in the soil for 90 d with Foc4 addition every 10 d. Soil microbial population analysis revealed that the culturable total fungal and bacterial populations increased and the culturable actinobacterial population decreased SixQ5 with addition. Pot experiments showed that Si5Q5 can reduce Foc4 infection in banana seedlings and does not harm banana seedlings. The stability and inhibitory effects on Foc4 demonstrate the potential application of SixQ5 in banana fields to prevent Foc4 conidial infection in the long term.