Effects of potassium humate on the population of Fusarium oxysporum f. sp. cubense in soil

Objective Fusarium oxysporum f. sp. cubense race 4 (FOC4) is the primary pathogen causing Fusarium wilt of banana. The goal was to study the effect of potassium humate on the FOC4 population dynamics in soil and the severity of Fusarium wilt.

Method Real-time quantitative PCR, microbial culture and artificial inoculation with FOC4 were employed to assess FOC4 abundance amended with different concentrations of potassium humate following FOC4 inoculation, as well as their effects on Fusarium wilt of banana.

Result At 30 days post inoculation (dpi), the abundance of FOC4 in soils amended with 16, 32, 64 and 96 g·kg⁻¹ of potassium humate was significantly lower than that in the control (CK). The counts of culturable bacteria and actinomycetes were significantly higher in potassium humate-treated soils than those in CK (P<0.05), whereas fungal counts were lower. Observations via laser confocal microscopy revealed that the FOC4 population decreased with increasing potassium humate concentration, with most propagules identified as conidia and a minority as hyphae. The disease incidence of Fusarium wilt of Brazilian banana in soils treated with different concentrations of potassium humate following FOC4 inoculation was analyzed. At 7 dpi, all Brazilian bananas showed symptoms except those in soils treated with 64 and 96 g·kg⁻¹ potassium humate. Nevertheless, the disease indexes of banana wilt in all potassium humate-treated groups were lower than that in the CK group.

Conclusion Application of potassium humate at 64 g·kg⁻¹ in soil reduces the FOC4 population and alleviates the severity of Fusarium wilt of banana.