Chitosan beads combined with Terminalia nigrovenulosa bark enhance suppressive activity to Fusarium solani

•Mixtures of CTB and T. nigrovenulosa bark showed antifungal activity on F. solani.•Mixtures of CTB and TNE inhibited root-rot disease of cucumber caused by F. solani.•PR-proteins increased in the leaves of cucumber treated with a mixture of CTB and TNE.•GPOD isozyme in leaves was expressed in 0.3% and 0.5% TNE treated with CTB. Chitosan beads (CTB) and Terminalia nigrovenulosa bark (TNB) were prepared using chitosan powder combined with T. nigrovenulosa powder (TNP) and T. nigrovenulosa extract (TNE) to obtain CTB+TNP (0, 1, 3, and 5%) and CTB+TNE (0, 0.1, 0.3, and 0.5%), respectively. The chitosan beads combined with TNB were tested for their antifungal activity against Fusarium solani. In vitro studies indicated that a mixture of 20 chitosan beads and 3–5% TNP inhibited F. solani mycelial growth the greatest. Mixtures of 10–20 chitosan beads and 0.3–0.5% TNE showed the greatest inhibition of F. solani mycelial growth. Total inhibition of F. solani mycelial growth was achieved with CTB and 5% TNP and CTB and 0.5% TNE after a 6 day incubation. Induction of pathogenesis-related proteins such as chitinase, β-1,3-glucanase, and guaiacol peroxidase were tested in cucumber seedlings. Enzyme accumulation was significantly higher in CTB and 0.5% TNE treated cucumber plants compared to that in control plants. We effectively demonstrated the biological activities of the CTB and TNP and CTB and TNE treatments. These results suggest that applying chitosan beads combined with TNB could be useful to control soil-borne diseases of cucumber seedlings.