The biocontrol by Streptomyces and Trichoderma of leaf spot disease caused by Curvularia oryzae in oil palm seedlings

This study aimed to apply the selected microorganisms Streptomyces hygroscopicus subsp. angustmyceticus NR8-2, Trichoderma harzianum TM2/1, and endophytic Trichoderma V76-12, to the control of leaf spot disease caused by Curvularia oryzae on oil palm leaves, in vitro, in vivo and in field conditions. The isolate V76-12 inhibited the growth of C. oryzae the most at 85.71% inhibition, followed by the isolates TM2/1 (75.71%) and NR8-2 (72.50%) in dual culture tests. Volatile antifungal effects were observed for V76-12 with 68% inhibition, followed by the isolates TM2/1 (45%) and NR8-2 (10%) in a bioassay. Crude metabolites of the isolates inhibited the mycelial growth of C. oryzae in agar diffusion tests. In pot experiments, the V76-12 gave disease severity index (DSI) of about 21%, similar to that with a reference chemical (20%), whereas TM2/1 and NR8-2 gave 66% and 75%, respectively. In naturally infested cases, oil palm seedlings treated with V76-12 showed 35.33% DSI, which is statistically significantly below those obtained with TM2/1, NR8-2 and the chemical (48.67%, 53.33% and 49.33%, respectively). The control treatment without antagonistic microorganisms gave the most severe DSI at 75.33%. The results also show that treatment with the selected isolates enhanced the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD), and polyphenol oxidase (PPO) enzymes in the oil palm. The V76-12 isolate was the most effective treatment tested in reducing leaf spot disease ...

Source: Biological Control - May 24, 2018 Category: Biology Source Type: research