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Research articles

ScienceAsia (): 584-590 |doi: 10.2306/scienceasia1513-1874...584


Biocontrol of Pythium aphanidermatum by the cellulolytic actinomycetes Streptomyces rubrolavendulae S4


Bajaree Loliama, Tsutomu Morinagab, Saipin Chaiyanana,*

 
ABSTRACT:     Streptomyces rubrolavendulae (Yen) S4, isolated from a termite mound in Kanchanaburi, Thailand, was used to control the seedling damping-off disease of the horticultural plant Joseph\'s coat caused by Pythium aphanidermatum (Edson) Fitz. In a previous study, S. rubrolavendulae S4 was shown to strongly inhibit the growth of P. aphanidermatum on potato dextrose agar. This study investigated the modes of the antagonistic action of S. rubrolavendulae S4 on P. aphanidermatum. On carboxymethyl cellulose medium, S. rubrolavendulae S4 produced the highest cellulase activity of 65 U/ml in 5 days. The S. rubrolavendulae culture supernatant, with and without heat treatment, was tested for fungal growth inhibition using an agar well-diffusion method. The inhibitory effect was retained with the heat inactivated culture supernatant, indicating that the inhibition was derived from an antifungal compound rather than an enzyme produced by S. rubrolavendulae S4. The parasitic activity of S. rubrolavendulae S4 upon P. aphanidermatum was demonstrated by light and scanning electron micrographs. Joseph\'s coat (Amaranthus tricolor) seedlings were grown in peat mosses inoculated with S. rubrolavendulae S4 and P. aphanidermatum. In pots containing S. rubrolavendulae S4, the proportion of healthy seedlings was significantly increased. This was equivalent to the effect of the fungicide metalaxyl, and similar to the results from sterilized peat moss. Hence S. rubrolavendulae S4 can be used as an effective biological control agent in Joseph\'s coat cultivation.

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a Department of Microbiology, Faculty of Science, King Mongkut\'s University of Technology Thonburi, 126 Pracha-utid Road, Bangmod, Toongkru, Bangkok 10140 Thailand
b Department of Life System Science, Graduate School of Comprehensive Scientific Research, Prefectural University of Hiroshima, 562, Nanatsuka, Shobara, Hiroshima, 727-0023, Japan

* Corresponding author, E-mail: saipin.cha@kmutt.ac.th

Received 7 Jan 2013, Accepted 18 Sep 2013