Cuminal Inhibits Growth Of Alternaria Alternata And Its Anitifungal Mechanism

Cuminal is one of the most components of cumin essential oil. Alternaria alternata is one of important pathogens that causes pre- and post-harvest losses at high frequency in many crops, which causes the occurrence of apple pears, apple, pepper, citrus, jujube, gingko,mango, apricot and persimmon black spot.There were little reports available on the underlying mechanism of antifungal function of cuminal against A. alternata. The methods of biochemistry, histochemical, scaning electron microscope and FACScan flow cytometer were used for investigating antifungal activity and its partial mechanism of cuminal.The aims of this study were to investigate the effects of cuminal on spore germination and in vitro hyphal biomass in A. alternata; to observe the morphological modification of changing; and to evaluate effects of cuminal in inducing cell membrane disruption and oxidation of lipids and triggering fungal cell death specifically through mitochondrial dysfunction-induced ROS accumulation, mitochondrial membrane potential variation, and mitochondrial dehydrogenase and ATPase activities. The results showed as below:1. Cuminal showed significantly against A. alternata in vitro. The MIC for the cuminal was 6.25 m L/L. Cuminal could obviously inhibit strains colony growth, spore germination,as well as hyphal biomass viability. At the same time, with the increasing of concentration of cuminal, the more significant of the inhibition effect. In addition, results of in vivo test showed that cuminal was effective in the control of black spot of pears inoculated with A.alternata.2. Observations using scaning electron microscope and transmission electron microscope revealed that there were morphological modifications, including mycelium asymmetry, hyphal swelling, curling, and a secretory appearance under the cuminal treatment. It showed that cuminal affect the normal physiological metabolism of A. alternata, resulting in the mycelium of a large number of malformation and death.3. The cuminal damaged membranes and decreased membrane integrity of spores. In addition, the ergosterol contents in mycelium treated with cuminal were continuously decreased during the incubation.The membrane damage consistently increased at different MDA concentrations, which indicated that cuminal induced oxidation of lipids. The above dysfunctions of the mitochondria caused ROS accumulation in spores. A reduction in cell viability was prevented through the addition of L-cysteine, which indicated that ROS is an important mediator of the antifungal action of cuminal.4. The chemical caused the degradation of MMP, and decreased ATPase and dehydrogenase activities in spores in a dose-dependent manner. Finally, a reduction in ATPcontent leads to the dysfunction of normal spores.In conclusion,cuminal had a well antimicrobial activity was related with the disruption of membrane integrity,decreasing the ergosterol contents, increasing MDA, MMP, ROS concentrations and the modification of mycelium morphology and ultrastructure.