Control of Chinese-kale damping-off caused by Pythium aphanidermatum by antifungal metabolites of Trichoderma virens

Seven strains of Trichoderma virens were isolated from Chinese-kale planting soil in Nakhon Si Thammarat province. Efficacy of those isolates to inhibit mycelial growth and overgrow on mycelia ofPythium aphanidermatum, a causal agent of damping-off on Chinese-kale, were determined by a dual culture test. All strains significantly inhibited growth and overgrew on mycelia of P. aphanidermatum on potato dextrose agar (PDA) as compared with the control. Strains T-NST-01, T-NST-05 and T-NST-07 gave high values of inhibition by 85.5, 82.5 and 78.5%, respectively. For efficacy to overgrow on mycelia of pathogen test, strains T-NST-05, T-NST-07 and T-NST-01 provided 48.3, 47.0 and 46.1% of mycelial overgrowth, respectively. Antifungal metabolites were extracted from three promising strains and tested against mycelial growth and sporangium production of P. aphanidermatum. The results showed that 1,000 mg/L of all metabolites completely inhibited mycelial growth and sporangium production. Under laboratory condition, all metabolites (1,000 mg/L) significantly increased the number of Chinese-kale seedling germination, especially the metabolites from T-NST-01 and T-NST-07 provided germination of 92.5 and 87.5%, respectively. Under glasshouse conditions, Chinese-kale seedlings treated with 1,000 mg/L of metabolites from strains T-NST-01 and T-NST-07 survived by 90.5 and 87.5%, respectively, while the control 1 (sterile water) and control 2 (2% methanol) had 19.0 and 18.5% of survived seedlings, respectively. In P. aphanidermatum viability test, mycelia of P. aphanidermatum treated with antifungal metabolites from three strains of T. virens showed no visible growth, while the control with 2% methanol or sterile water, mycelia of P. aphanidermatum rapidly grew and covered whole surface of PDA in of the Petri dish within 4 days

Use of Promising Bacterial Strains for Controlling Anthracnose on Leaf and Fruit of Mango Caused by Colletotrichum gloeosporioides

A total 146 isolates of bacteria were taken from leaf surface, fruit skin, and blossom of mango (var. Nam Dorkmai). They were tested for the inhibition of mycelial growth of Colletotrichum gloeosporioides, a causal agent of anthracnose, on potato dextrose agar (PDA). Seventy-four bacterial isolates inhibited the growth of fungal mycelia by 24.51-49.10%. The 40 highly effective isolates out of 74 isolates were further tested for the potential to reduce the development of anthracnose lesion on detached leaves of mango marcotages at 24 h after inoculation of pathogen. Results indicated that 12 isolates provided high efficacy for inhibiting disease by 51.39-86.11%. Application of these bacteria on mango fruits at 24 h prior to the inoculation of the pathogen revealed that isolates B46 and B12 suppressed disease by 50.36 and 44.13% respectively while Trichoderma harzianum CB-Pin-01 provided 37.30% of the inhibition. For controlling post-harvest disease, an isolate B12 or B12 integrated with hot water treatment (55 oC) provided 91.33 and 88.00% of disease severity reduction respectively when applied at 24 h before inoculation of pathogen. Isolates B12 and B44 were identified as Bacillus subtilis while B46 and K112 were B. licheniformis and B. cereus respectively. The mechanism of these isolates for controlling C. gloeosporioides was the reduction of spore germination and the inhibition of germ-tube elongation