Effects of medicinal plant extracts and antagonistic microorganisms on growth of pathogenic fungus of ginger rhizome rot during storage
2002
Chawalert Trikarunasawat(Kasetsart University. Kamphaeng Saen Campus, Nakhon Pathom (Thailand). Faculty of Agriculture. Department of Plant Pathology) | Vichai Korpraditskul(Kasetsart University. Kamphaeng Saen Campus, Nakhon Pathom (Thailand). Faculty of Agriculture. Department of Plant Pathology)
Fusarium oxysporum was isolated and identified as causal organism of ginger rhizome rot during storage. Two hundred and sixty six isolates of microorganism were isolated from soil, root and rhizome samples, which were collected from 12 ginger fields in Northern, Northeastern and Southern part of Thailand. All isolates were tested for antagonistic ability to the pathogenic fungi (Fusarium oxysporum) by spot inoculation method. Forty-seven isolates of fungi and 17 isolates of bacteria showed their ability as antagonistic microorganism. Crude extracts of 31 dry medicinal plant species were extracted with 95 percent ethanol and tested for the efficacy on growth inhibition of F. oxysporum by filter paper disc method. Two species of medicinal plant extracts namely betal vine leaves (Piper betal L.) and clover (Syzygium aromaticum L.) at 100,000 ppm inhibited negative growth 78.27 and 65.49 percent, respectively compared to 1,000 ppm of Imazalil fungicide. The solvent partition with petroleum ether and ethylacetate revealed that active compound in clove was low polarity compound while the betal vine leave was moderate polarity compound. The enhance the efficacy of antagonistic microorganisms, three chemicals, namely D-fructose CaCl2 and chitosan, were tested by poisoned food technique on vegetative growth of F. oxysporum. The results showed that Chitosan at 0.6 percent gave the highest growth inhibition percentage, 75.33 percent, whereas CaCl2 at 4 percent gave 66.67 growth inhibition percentage. The concentrations of CaCl2 lower than 1 percent and all concentration of D-fructose (0.5 to 4 percent) slightly stimulated the vegetative growth of the pathogen.
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