Studies On Inhibitory Mechanism Of Natamycin To Botrytis Cinerea On Postharvest Of Grapes

Natamycin was a polyene macrolide antibiotic that can selectively inhibit yeast and mold,the inhibition mechanism of biological antibacterial agents as Natamycin was mostly in biochemical methods.The Botrytis cinerea of grape postharvest were used as test material,the research orientation were cells and subcellular,metabolism and molecular level respectively,all this will serve as some theoretical foundations in control of postharvest B.cinerea for table grape storage and transportation.On the physiological metabolism level,the bioassays as mycelium growth inhibition rate,dry weight,sporulation yields,spore germination inhibition rate,mycelium conductivity and ergosterol content of B.cinerea under different concentrations treatment of natamycin were observed in this experiment,the results shows that the higher the concentration of natamycin was,the higher the mycelium growth inhibition rate and spore germination inhibition rate was,the lower the mycelium dry weight and the sporulation yields was;500 mg/L natamycin bacteriostat enjoys its inhibition ratio as 87.28%and 64.349%respectively on mycelium growth and spore germination of gray mold,and the dry cell weight of B.cinerea and spore germination reduce for 58.86%and 69.62%respectively as compared with control groups,each indicators did not change significantly when the concentrations of natamycin was increased.The B.cinerea mycelium conductivity treated by natamycin was enhanced rapidly as the extension of time.After 10 hours,the cell membrane permeability was 70.57%±3.09%under the concentration of 500 mg/L,and the ergosterol content of mycelium was only 48.60μg/g±3.82 μg/g when cultured 3 days under the same concentration;The artificial inoculation tests indicate that with the treatment concentration as 500 mg/L,fruit surface lesion area was only 26.103 mm2.On the molecular level,the expression of BcPG1、BcPG2 and BcPG3 genes were not observed any differences when treated by natamycin,all the three genes were related with polygalacturonic acid enzymes secretion;while the expression of CYP51 gene which encoding sterol 14-a demethylases was increased,and the ERG27 gene which encoding sterol 3-keto reductase was decreased,both two genes were related with ergosterol synthesis in fungal cell membrane.On the cells and subcellular level,the scanning electron microscopy and transmission electron microscopy were used to observed,the mycelium surface was appeared shrinking when treated with natamycin,and the growing point was found deformity;In ultrastructure,the mycelium cell wall were uneven or thickening,cell membrane were partly dissolved,the cell contents were exosmosised,mitochondria and other organelles were dissolved,and plasmolysis occurred.