Biodiversity of endophytic actinobacteria from jasmine rice (Oryza sativa L. KDML 105) grown in Roi-Et Province, Thailand and their antimicrobial activity against rice pathogens

摘要

The aims of this study were to investigate endophytic actinobacteria from jasmine rice (Oryza sativa) L. KDML 105 and their antimicrobial activity against rice pathogens. Three rice samples were collected from the rice paddy fields in Suvannabhum District, Roi-Et Province, Thailand. Roots, stems, leaves and leaf sheaths were surface-sterilized prior to incubation on four different isolation media at 27 and 37?°C. One hundred and sixteen isolates were obtained. Colony and spore morphology accompanied with 16S rRNA gene sequencing were used to identify all the isolates. There were 63 Streptomyces isolates (54.3?%), 50 Microbispora isolates (43?%) and 3 Kineococcus isolates (2?%). All the isolates were tested for antimicrobial activity against rice pathogens; Xanthomonas oryzae KHWK 4.1_UBN_06, Pyricularia grisea 61119, Helminthosporium oryzae DOAC 1570 and Curvularia lunata BCC 15558 by using a dual-culture technique. The results showed that twenty-two and four isolates (18.8 and 3.4?%) showed good activity against X. oryzae KHWK 4.1_UBN_06 and P. grisea 61119, respectively. Most of the active isolates belonged to the genus Streptomyces. Selected isolates which showed good activity against test microorganisms were screened for PKS-I, PKS-II and NRPS genes. None of the isolates contained these functional genes, which revealed that antimicrobial activity did not correlate to these genes. In conclusion, as endophytic actinobacteria from rice can inhibit rice pathogens in vitro they can be further evaluated to select for activity in suppressing pathogens in pot experiments. The effective strains can be further studied for development as biocontrol agents.