Effect Of Calcium On T-2 Toxin Induced Active Oxygen Metabolism And Wound Healing In Potato Tubers

Dry rot caused by Fusarium spp.is the main post-harvest disease of potato tubers,and trichothecene mycotoxins are produced in diseased tubers,of which T-2 toxin is the most important composition.Our previous study indicated that T-2 toxin induced resistance of potato tuber,which was closely related with active oxygen metabolism,however,the detailed mechanism of action is unknown.In this study,the original potato tubers'cv.Longshu 3'was used as the test material.The tubers were cut in half and treated with T-2 toxin,CaCl₂ and calcium chelator EGTA.The treated tubers were assayed the lesions diameter of tubers inoculated with F.sulphureum,observed the accumulation of suberin poly phenolic?SPP?and suberin poly aliphatic?SPA?,and analyzed the active oxygenand phenylpropanoid metabolism related enzyme activities and metabolite content.The results showed as below:1.Calcium treatment inhibited the lesion diameter and weight loss of tubers treated with control and T-2 toxins to some extent,and promoted the accumulation of SPP and SPA.EGTA significantly increased lesion diameter and weight loss of the control and T-2toxin-treated inoculated tubers,and inhibited the accumulation of SPP and SPA.2.Calcium maintained the integrity of the cell membrane of tuber,significantly increased the activity of NADPH oxidase?NOX?and superoxide dismutase?SOD?,and increased the O₂^-.production rate and H₂O₂ content of tubers treated with T-2 toxin.EGTA significantly reduced the integrity of the cell membrane,and the rate of O₂^-.production and H₂O₂ content in tubers,and inhibited the activity of NOX,SOD,catalase and peroxidase.3.Calcium had no significant effect on the activity of ascorbate peroxidase?APX?,glutathione reductase?GR?,dehydroascorbate reductase?DHAR?,and monodehydroascorbate reductase?MDHAR?,however,increased the content of ascorbic acid?ASA?,dehydroascorbic acid?DHA?and glutathionein?GSH?in tubers treated with the control and T-2 toxins.EGTA significantly reduced the activity of APX,GR,DHAR and MDHAR,and inhibited the accumulation of GSH,GSSG and DHA in tubers treated with the control and T-2 toxin.4.Calcium increased the phenylalanine ammonia-lyase?PAL?activity of tubers treated with the control and T-2 toxins,promoted the accumulation of flavonoids,total phenols,and lignin in tubers treated with the control and T-2 toxin.EGTA reduced PAL activity andthe content of total phenol,flavonoid and lignin in tubers treated with the control and T-2 toxin.It is suggested that calcium treatment increases resistance of potato tubers induced by T-2 toxins,which closely related to maintain the integrity of cell membranes,to increase the activity of enzymes involved in the active oxygen metabolism,and to promote the accumulation of ASA,DHA and GSH.Calcium also activates phenylpropane metabolism,acuumulates SPP,SPA,total phenols,flavonoids and lignin at the wounded sites,promotes the wound healing of harvested potato tuber.