Abstract
Pythium genus includes significant and destructive soil borne plant pathogens causing losses on many plants, especially by root rot and damping-off diseases. Like other soil borne pathogens, control of the diseases caused by this group is rather difficult. Usually fungicides are used against Pythium species, but investigations on alternative methods and chemicals gained importance because of the harmful effects of pesticides on human health and environment. Plant extracts and essential oils are among the safer alternative chemicals. Since oregano oil has high fungitoxic effect even in low concentrations, effect of oregano water, by-product of oregano oil, was investigated in this study against P. deliense, one of the most common and virulent species in Turkey. Oregano water obtained from Origanum onites, diluted with distilled water in 100, 80, 60, 40, 20, 10 and 5% rates was applied to soil and its effects on P. deliense population density in soil and severity of damping-off disease on bean plants caused by the pathogen were determined. As a result, all solutions containing oregano water over 10% rate significantly decreased pathogen populations in the soil samples taken every three days after the applications, and the least pathogen density was obtained with undiluted oregano water. Similarly, undiluted oregano water increased emergence rates of the bean seedlings and significantly decreased root and hypocotyl rot severity by suppressing the effect of the pathogen. In addition, application of oregano water supported the shoot and root development of the plants by decreasing the negative effect of the pathogen on plant growth. This study showed that oregano water was an effective alternative against Pythium related damping-off disease.
Highlights
Pythium genus, belonging to Phylum Oomycota of the Chromista Kingdom, includes species, parasitic on different organisms such as fish, insects, fungi and even on human
This study showed that oregano water was an effective alternative against Pythium related damping-off disease
Pathogen inoculum reached 370 propagules per gram of soil in the samples taken from the containers sprayed with sterile distilled water representing control group, while the density of the pathogen decreased in the soil samples depending on the dilution rate of oregano water
Summary
Pythium genus, belonging to Phylum Oomycota of the Chromista Kingdom, includes species, parasitic on different organisms such as fish, insects, fungi and even on human. Pythium species are especially common in rhizosphere soil, prefer young and watery plant tissues and cause pre or post-emergence damping-off symptoms on young plants They can decrease yield by causing root rot and suppressing growth of older plants. It is first isolated from tobacco plants showing stem blight symptoms in Sumatra It is known as a pathogen living mostly in warmer soils with an optimum growth temperature of 36°C (Yu and Ma, 1989). It is isolated from cabbage (Yu and Ma, 1989), tomato, mung bean, ginger, pawpaw, lettuce, bitter melon and cowpea (Lodha et al, 2004). It is reported as a common pathogen in vegetable and tobacco nurseries and that
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