การควบคุมโรคใบจุดของหญ้าหวานด้วยเชื้อแอคติโนแบคทีเรีย

Abstract

In this study, stevia leaf spot is present in stevia production fields in Chiang Mai, Thailand. Identification based on morphology and molecular characters confirmed the isolates used identified as were Septoria steviae and Curvularia sp. Thirty-eight isolates of actinobacteria isolated from Rosaceae and herbal plants were used to evaluate their inhibitory effects on growth of leaf spot pathogen of stevia (Stevia rebaudiana Bertoni). Five isolates of actinobacteria as follows CINv1, CINv2, CINc1, COF1 and PRE5 were highly efficient inhibit the radial showed of these two fungal diseases and showed the percent inhibition of radial growth (PIRG) more than 75%. PRE5 had the highest PIRG (95.67 %) of Curvularia sp. For S. steviae, it was found that the 5 isolates of actinobacteria had a very high PIRG (100%). Stevia tissue culture plantlets were further proved for colonization by these 5 actinobacteria using re-isolation method. The results found that isolates CINv1, CINv2 and PRE5 successfully colonized leaf and stem tissue, followed by CINc1 and COF1. The growth promoting abilities of these selected actinobacteria tested in vitro and in vivo, COF1 was able to best promote the height. In addition, actinobacteria efficacy test for inhibiting the growth of stevia leaf spot disease in greenhouse conditions showed that stevia containing actinobacterial isolate COF1 induces resistance to both types of fungi. Tests the efficacy of the inhibition growth of leaf spot disease in vivo condition, COF1 induces resistance to both types of fungi with the best percent inhibition of disease incidence and the lowest disease severity index, followed by CINv2, CINc1, CINv1, and PRE5 respectively. The actinobacteria was identified as Streptomyces albus, based on morphology and molecular characters.