Effects Of Heat And Potassium Sorbate In Resistance To Gray Mold And Storage Effectiveness On Kiwifruit

The effectiveness of heat and potassium sorbate on gray mold(Botrytis cinerea)control and postharvest quality of ’xuxiang’ kiwifruits during storage were evaluated.At room temperature(24℃)and cold stress(0℃),using sterile water as the control(CK),5 g/L(w/v)potassium sorbate(PS)and 48℃ heat(HT)were chosen to evaluate the inhibitory effects on the gray mold of kiwifruit.The effects of lesion diameter,disease index,resistance-related enzyme activity and related genes expression level by inoculated Botrytis cinerea were analyzed.In order to determine the effect of 48℃ heat(HT)and 5 g/L potassium sorbate(PS)on kiwifruit quality,soluble solid content(SSC),titratable acidity(TA),ascorbic acid,firmness,weight loss rate,natural decay incidence and other physiological indicators were measured.Following a set of pretreatments,kiwifruits were stored at 0±0.5℃,RH 85±5% for 90 d.The main research results are as follows:1.Effects of different treatments on resistance to Botrytis cinerea in vitro.In vitro,compared with CK,PS,HT and PS+HT treatment can inhibit the growth of mycelium and spore germination.There was no significant(p>0.05)difference of colony diameter between HT and CK at 7 d,but HT could inhibit 66.67% spore germination,and the length of germ tube was significantly smaller than CK(p<0.05).PS can effectively controll the expansion of colony diameter by inhibitting the germination of spores and the elongation of the germ tube.In addition,PS+HT treatment could completely inhibit the growth of Botrytis cinerea.2.Effects of different treatments on induction of resistance to Botrytis cinerea in vivo.In vivo,whether at room temperature or cold stress,PS,HT and PS+HT treatment significantly reduced the development of gray mold decay in kiwifruits,and remarkably enhanced activities of defense related enzymes including polyphenol oxidase(PPO),peroxidase(POD),chitinase(CHI),β-1,3-glucanase(GLU)and phenylalanine ammonialyase(PAL).The treatment decreased the accumulation of malondialdehyde(MDA)content,and increased the total phenolic content.Meanwhile,PS+HT treatment had higher CHI and GLU expression level.In addition,There was no significant(p>0.05)difference of lesion diameter between PS,HT and CK in anaphase storage.The incidence index of PS+HT treatment at room temperature(7 d)and cold stress(30 d)was 29.97% and 27.35%,respectively,which was significantly lower than that of CK,PS and HT(p<0.05).3.Effects of different treatments on kiwifruit qualityHT,PS and PS+HT effectively improved flavor and taste during storage and shelf life,slowed down the rate of conversion of TA and ascorbic acid,reduced the respiration rate,delayed the softening of kiwifruit,improved the activity of enzyme(PPO,POD)and decreased the decay rate and weight loss rate.Moreover,PS+HT treatment had the best effect on kiwifruit,compared with other treatment.The weight loss rate and decay rate of kiwifruit was only 2.11% and 0 at 90 d,while the control already reached 4.61% and 3.08%.In addition,HT treatment delayed the occurrence of chilling injury during storage,reduced the chilling injury index,and had better effect combined with PS.All of above indicated that PS+HT could significantly improved the quality of kiwifruit,reduced postharvest decay.