Chitosan-cinnamon beads enhance suppressive activity against Rhizoctonia solani and Meloidogyne incognita in vitro.

A novel chitosan-cinnamon bead carrier was prepared in this study. Chitosan was mixed with cinnamon powder (CP) and cinnamon extract (CE) to obtain chitosan-cinnamon powder (CCP) beads and chitosan-cinnamon extracted (CCE) beads, respectively. The potential antifungal and nematicidal activities of CCP and CCE were investigated against Rhizoctonia solani and Meloidogyne incognita in vitro. Relative antifungal activity of the CCP (5% CP) bead-treated R. solani was 30.9 and 23.9% after 1 and 2 day incubations, respectively. Relative antifungal activity of the CCE (0.5% CE) bead-treated R. solani was 4.3, 3.0 and 4.2% after 1, 2 and 3 days of incubation. Inhibition of hatch by CCP beads with CP of 5% was 78.8%. Inhibition of hatch by CCE beads with CE of 0.5% was 82.0%. J2 mortality following the CCP (5% CP) and CCE (0.5% CE) bead treatments was 85.0 and 95.8%, respectively against M. incognita after 48 h incubations.

Antifungal activity of gallic acid purified from Terminalia nigrovenulosa bark against Fusarium solani.

The antifungal activities of methanolic extracts from Terminalia nigrovenulosa bark (TNB) was investigated for effects on the initial growth of mycelia against Fusarium solani. The ethyl acetate fraction separated from TNB demonstrated the highest antifungal activity against F. solani. The antifungal compound was isolated from TNB using silica gel column and Sephadex LH-20 chromatography combined with thin-layer chromatography and high performance liquid chromatography. Structural identification of the antifungal compound was conducted using (1)H NMR, (13)C NMR, and liquid chromatography-tandem mass spectrometry. The purified antifungal compound was gallic acid (GA) or 3,4,5-trihydroxy benzoic acid. Purified-GA possesses the high antifungal activity against F. solani, and that antifungal activity was dosage-dependent. The hyphae became collapsed and shrunken after 24 h incubation with GA (500 ppm). In pot experiments, the application of TNB crude extract was found to be effective in controlling the cucumber Fusarium root rot disease by enhancing activities of chitinase, peroxidase thereby promoting the growth of plants. The applied TNB extract significantly suppressed root rot disease compared to control. It resulted in 33, 75 and 81% disease suppression with 100, 500 and 1000 ppm of TNB crude extract, respectively. The study effectively demonstrated biological activities of the TNB extract, therefore suggesting the application of TNB for the control of soil-borne diseases of cucumber plants.

Nematicidal activity of 3,4-dihydroxybenzoic acid purified from Terminalia nigrovenulosa bark against Meloidogyne incognita.

In this study, the 3,4-dihydroxybenzoic acid (3,4-DHBA) from Terminalia nigrovenulosa bark (TNB) was purified and its in vitro nematicidal activity was investigated against Meloidogyne incognita. The purification of 3,4-DHBA used a silica gel column and Sephadex LH-20 chromatography combined with thin-layer chromatography and high performance liquid chromatography. Structural identification of the 3,4-DHBA was conducted using (1)H nuclear magnetic resonance (NMR), (13)C NMR, and liquid chromatography time-of-flight mass spectrometry. Nematicidal activity bioassays revealed that 3,4-DHBA treatment resulted in 33.3, 47.5, 72.5 and 94.2% J2 mortality at 0.125, 0.25, 0.5 and 1.0 mg/ml, respectively after 12 h incubation. J2 mortality was increased significantly (P < 0.0001) with increasing incubation time in the range of 54.2-94.2% from 3 to 9 h after incubation with 3,4-DHBA (1.0 mg/ml), but with no significant difference observed where the incubation time was increased from 9 to 12 h. The 3,4-DHBA treatment resulted in 33.3, 65.0, 76.7 and 85.0% hatch inhibition at 0.125, 0.25, 0.5 and 1.0 mg/ml, respectively, 3 days after incubation. Changes in the shape of the eggs were determined after incubation for 1 day with a 3,4-DHBA concentration of 1.0 mg/ml.

Induction of defense response against Rhizoctonia solani in cucumber plants by endophytic bacterium Bacillus thuringiensis GS1.

An endophytic bacterium, Bacillus thuringiensis GS1, was isolated from bracken (Pteridium aquilinum) and found to have maximal production of chitinase (4.3 units/ml) at 5 days after culture. This study investigated the ability of B. thuringiensis GS1 to induce resistance to Rhizoctonia solani KACC 40111 (RS) in cucumber plants. Chitinase activity was greatest in RS-treated plants at 4 days. beta-1,3- Glucanase activity was highest in GS1-treated plants at 5 days. Guaiacol peroxidase (GPOD) activity increased continuously in all treated plants for 5 days. Ascorbate peroxidase (APX) activity in RS-treated plants was increased 1.5-fold compared with the control at 4 days. Polyphenol oxidase (PPO) activity in RS-treated plants was increased 1.5-fold compared with the control at 3 days. At 5 days after treatment, activity staining revealed three bands with chitinase activity (Ch1, Ch2, and Ch3) on SDSPAGE of cucumber plants treated with GS1+RS, whereas only one band was observed for RS-treated plants (Ch2). One GPOD isozyme (Gp1) was also observed in response to treatment with RS and GS1+RS at 4 days. One APX band (Ap2) was present on the native-PAGE gel of the control, and GS1- and GS1+RS-treated plants at 1 day. PPO bands (Po1 and Po2) from RS- and GS1+RS-treated plants were stronger than in the control and GS1-treated plants upon native-PAGE at 5 days. Taken together, these results indicate that the induction of PR proteins and defense-related enzymes by B. thuringiensis GS1 might have suppressed the damping-off caused by R. solani KACC 40111 in cucumber plants.