Studies Of ?-Phellandrene And Nonanal's Inhibition Effect On Penicillium And Botrytis Cinerea

Blue mold and gray mold are the main diseases of tomato fruit —,which arecaused by the pathogens Penicillium cyclopium and Botrytis cinerea..Until now,the means of prevention and control mainly rely on traditional chemical methods.Although traditional chemical fungicides have better control effect,yet they have some shortcomings of high toxicity,high pollution and long-term use of easy to make pathogens resistant.In recent years,more and more attention have been paid to biological methods to control fruits and vegetables decay,in particular,the use of plant volatiles or plant essential oils to inhibit bacteria have become a hot topic.Plant volatile substances and essential oils have the advanteges of no pollution,low cost,and obvious effect,in particular,citral,limonene,cinnamaldehyde,and other aidehydes have obvious antibacterial effect which have been proved by experiments by relevant experts and scholars,and they provide a wide space for the prevention and control of tomato fruit rot.In the experiment,?-phellandrene and nonanal as antimicrobial agents were tested for in vitro and in vivo against Penicillium cyclopium and Botrytis cinerea,and the antibacterial effect was studied,which provided a new way for disease prevention and preservation of fruits and vegetables,a new method was explored.In the vitro experiment,through bacteriostasis experiment,the inhibitory concentrations of two kinds of bacteriostatic agents on two fungi were detemined.The effects of ?-phellandrene and nonanal on the growth of Penicillium cyclopium were determined by agar dilution culture method.The MIC and MFC of ?-phellandrene and nonanal were determined,The growths of fungi with ?-phellandrene and nonanal treatment were observed by scanning electron microscopy.The indexes suah as intracellular solution leakage,extracellular pH,extracellular conductivity,extracellular K~+,fungal lipid contents werecompared between control and treated group,and the mechanism of bacteriostasis was explored.In the in vivo experiment,the effects of inhibitors on tomato fruits were studied bycounting fruits' decay rate and measuring water loss rate,firmness,pH and TSS of tomato fruit,key enzymes of antioxidant enzymes(SOD?CAT?POD?PAL)in tomato fruits,and the changes of total phenolics and flavonoids content.The main results are summarized as follows:In vitro bacteriostatic test,?-phellandrene and nonanal had inhibitory effect of different concentration of Penicillium cyclopium and Botrytis cinerea.The MIC andMFC of ?-phellandrene on Penicillium cyclopium was 170 ?L/L,180 ?L/L,respectively.The MIC and MFC of nonanal on Penicillium cyclopium was 25 ?L/L,45 ?L/L,respectively.The MIC and MFC of ?-phellandrene on Botrytis cinerea was160 ?L/L,220 ?L/L,respectively.The MIC and MFC of of nonanal on Botrytis cinerea was 25 ?L/L,50 ?L/L,respectively.Therefore,the antibacterial effect of nonanal was better than that of ?-phellandrene.After nonanal and ?-phellandrene treating Penicillium cyclopium and Botrytis cinerea,the changes of intracellular solution leakage,extracellular conductivity,extracellular pH,extracellular K~+,fungal lipid contents were determined.The results were showed that the two fungi were the increase in leakage of nucleic acid,extracellular conductivity,extracellular pH,K~+leakage in the presence of the bacteriostatic agent,,indicating that the bacteriostatic agent caused a large number of bacterial cell leakage,and the lipid content decreased obviously,which indicated that the structure of fungal cell membrane might be changed.The microscopic morphology of the fungi was observed by scanning electron microscopy,found that fungal mycelium stipes were distorted,and even the strain emerged in spiral shape and the depression of conidium were serious,which was further confirmed that the bacteriostatic agent destroyed the cell membrane structure of Penicillium cyclopium,and then increased their permeability,a large number of intracellular material were leaked,thereby inhibited the growth of Penicillium cyclopium.In vitro experiments,we chose nonanal as bacteriostatic agent in vivo,which had better bacteriostatic effectiveness.The results showed that higher concentration of nonanal had better inhibitory effect against Penicillium cyclopium and Botrytis cinerea,and lower decay rate of tomato fruit caused by fungi.The fruit quality indexes of each treatment group were determined,such as firmness,Vc content and TSS content.They could been found that nonanal had no significant effect on tomato fruit quality,could induce antioxidant activity in tomato,and increase defense antioxidant enzymes(SOD,CAT,POD,PAL),and then phenolic compounds and flavonoids contents were increased,their own resistance to Penicillium cyclopium and Botrytis cinerea were improved,reduced the rotting rate of the fruits.