Selection of Endophytic Actinomycetes Against Fruit-rot Fungi of Longan

Abstract

Fruit peels of Longan cv. Dor was used for isolation and gained 24 isolates of endophytic actinomycetes. Their morphological studies, mycelia growth, branching and arrangements of spore chain observed under microscope were possibly exhibited the genus Streptomyces sp. To select the superior isolates on mycelial growth inhibition for three genera of fruit-rot fungi of longan, screening tests were obtained in the isolates of DIM8, DIM9, DIM15 and DIM19 on Pestalotiopsis sp., DIM4, DIM12, DIM15, DIM16, DIM20 and DIM25 on Lasiodiplodia sp. and the isolates of DIM3, DIM5, DIM15, DIM25 and DIM26 on Trichothecium sp. The inhibition effects on the pathogens were also compatibly compared with those of CEN26, COF4, GAR1, HOU2 and NEE1 group of the isolates obtained from the previous experiment. In addition, their antimicrobial substance productions in different media were also proved that dual culture testing on ISP-2 agar shown more increasing of inhibition percentages than the testing on IMA-2 agar observed in both group of them. Particularly, the DIM15 was the best isolate revealing very high inhibition percentages on Pestalotiopsis sp. and Lasiodiplodia sp. at 87.10 and 73.82 on ISP-2 agar which were 86.43 and 80.58 percents higher than the testing on IMA-2 agar, respectively. In case of Trichothecium sp., GAR1 isolate significantly showed the most inhibition percentage at 89.68 which was significantly better than the DIM15 isolate. Moreover, GAR1 isolate is preferable to produce antifungal substance on ISP-2 agar than the others. These results revealed that DIM15 and GAR1 isolates showed their potentials to be used as alternate means for reduction of agrochemical application in post harvest disease control of longan fruit in the future.