Original Article | 2012, Vol.34, No.4, pp. 387-393
Screening of chitinolytic actinomycetes for biological control of Sclerotium rolfsii stem rot disease of chilli
Pranee Pattanapipitpaisal and Rillapat Kamlharn
pp. 387 - 393
Abstract
Two hundred and eighty three strains were isolated from rhizoshere-associated soils, from Ubon Ratchathani and Srisaket province, using Enrichment Media for isolation of Chitinase-producing Actinomycetes agar (EMCA agar). All strains were screened for chitinolytic activity and sixty eight strains gave significant clear zone on EMCA agar plates. The selected chitinolytic strains were assayed for in vitro antagonism against Sclerotium rolfsii using cornmeal agar (CMA agar) assay procedure and the result showed that thirteen isolates have remarkable inhibiting the growth of the fungus and the top five antagonistic actinomycetes were PACCH 277, PACCH129, PACCH225, PACCH24 and PACCH246, respectively. The result indicated that these actinomycetes produce chitinase which catalyze the degradation of chitin, resulting in inhibition of S. rolfsii growth. Their abilities to control the disease development were tested for in vivo biocontrol assay on chilli seedlings. Two out of thirteen candidate, PACCH24 and PACCH225, antagonists reduced the disease development at 90%. It was suggested that the ability to inhibit the growth of pathogen in vitro was not related to the disease reduction in vivo. The strain PACCH24 was further identified as Streptomyces hygroscopicus according to morphological characteristic, cell wall and cellular sugar analysis and 16S rDNA sequencing. The study implies a novel chitinolytic actinomycete which could be developed to be a biological agent which would be included as a complement with organic fertilizers in order to control stem rot disease and promote growth of chilli.
