Melanin inhibitors and dithiocarbamate interconversion in some phytopathogenic fungi

الملخص EN

The concentration of the fungicide Zineb required to inhibit 50 and 90% of mycelial growth for the melanotic fungi was relatively high.

Sclerotium cepivorum appeared to be more sensitive to carboximide than Fusarium oxysporum.

Alternaria solani was comparatively the least sensitive.

The inhibition of fungal growth by Zineb was reversed by a tocopherol and the effect appeared to be dose dependent.

Fifty percent inhibition of growth led to an accumulation in their lipid peroxide contents in the 3 tested fungi as compared to that in the absence of fungicide.

This increase in lipid peroxide was reversed by addition of a tocopherol to Zineb growth culture.

The former being a lipophilic antioxidant could eliminate the oxidant free radicals initiated by Zineb.

Resistance factors of the 3 melanotic increased by inclusion of dopamine, melanin precursor, in Zineb growth culture.

On the other hand, the melanin inhibitors Na2 EDTA really increased the inhibitory effect of fungicides in the three tested pathogens.

A clear correlation exists between the presence of some melanin inhibitors in Zineb growth cultures and the retardation in fungicide sensitivity values.

The resistance factor as dropped by about 25 to 40%.

The evidence for a relationship between melanization and resistance to oxidant thus seems very strong, leading the elimination of the inhibitory effect of the fungicide.

To improve the effectiveness of carboximide fungicides, in general, it be associated with selective melanin inhibitors particularly in controlling melanotic pathogens either in plant pathology or in medicinal field, under relatively low oxidative stress