SA, MeJA And O₃ Enhanced The Biocontrol Efficacy Of Antagonistic Yeast To The Postharvest Disease Of Fruits

Great economical losses which caused by postharvest fungal disease of fresh fruits are serious in the world.Control of postharvest diseases of fruits normally carried out by the application of fungicides.However,due to the development of fungicides-resistant isolate of pathogen,the residue of fungicides and concern for public safety,environment pollution and so on,it is necessary to develop alternative control methods to control postharvest diseases.Biological antagonists had demonstrated an efficient way for controlling postharvest diseases of fruits,reducing fungicidal dosage,thus increasing the food safety and reducing latent environmental danger.However,application of antagonist alone is not as effective in controlling postharvest diseases as using chemical fungicides.In order to enhance the biocontrol activity of antagonistic yeasts,this study was mainly to investigate the efficacy and mechanisms of salicylic acid(SA),methyl jasmonate(MeJA) and ozone(O₃) to enhance the control activity of antagonistic yeasts to postharvest diseases of fruits.1.Biocontrol efficacy and its mechanism of R.glutinis enhanced by salicylic acid to control the mold of postharvest strawberry fruits were studied by investing the effects of antagonists,pathogen and fruits treated with SA.Combination of R.glutinis (1×10⁸ CFU/ml) and SA(100μg/ml) significantly inhibited the gray mold,blue mold and Rhizopus rot diseases in strawberries more significantly than the applications of SA or R.glutinis alone.The disease incidence of gray mold,blue mold and Rhizopus rot of strawberries treated with the combinational treatment were 40%,31.77%, 19.64%of that in the control,and the lesion diameter were 18.18%,26.32%,35.71% of that in the control respectively.High concentrations of SA(100-1000μg/ml) significantly inhibited the spore germination of B.cinerea,P.expansum and R. stolonifer,however,it did not inhibit the mycelia growth of B.cinerea and P. expansum in PDA.SA at the concentration of 100μg/ml significantly increased the population of R.glutinis both in vivo and in vitro.SA alone or combined with R. glutinis increased the activity of POD,PAL,GLU and CHT,and reduced the activity of LOX and the content of MDA in fruits.The combined treatment of SA and R. glutinis significantly inhibited the natural infections and had no significant effect on quanlity of fruits compared to the control.2.Biocontrol efficacy and its mechanism of R.glutinis enhanced by salicylic acid to control the mold of postharvest peach fruits were studied.The combined treatment of SA(100μg/ml) with R.glutinis(1×10⁸ CFU/ml) produced significant increase in the control of Rhizopus rot,gray mold and blue mold rot of peaches.The disease incidence of gray mold,blue mold and Rhizopus rot treated with the combinational treatment were 30%,37.5%,20.83%of that in the control,and the lesion diameter were 25.87%,59.22%,52.47%of that in the control respectively.SA remarkably inhibited the population of B.cinerea in PDA;however,it did not inhibit P.expansum.SA at concentration of 1-100μg/ml had no significant effect on the growth of R.glutinis both in vivo and in vitro;while,SA at 1000μg/ml could significantly harmper the population of R.glutinis in peach wounds.R.glutinis alone or combined with SA increased the activity of POD,PPO and reduced the content of MDA,respiration rates,browning degree and membrane permeability rats in peach fruits.The combination of SA and R.glutinis significantly inhibited the natural infections and had no significant effect on quality of nature peach fruits.3.Biocontrol efficacy and its mechanism of R.glutinis enhanced by methyl jasmonate to control the mold of postharvest pears were studied.Treated with MeJA at the concentrations of 100-500μmol/l had significant influence in reducing gray mold incidence in pear fruits.However,it had little effect on controlling blue mold of pears.MeJA at 200μmol/l significantly enhanced the efficacy of R.glutinis in reducing the gray mold and blue mold decay of pears.The combined treatment MeJA (200μmol/l) with R.glutinis(1×10⁸ CFU/ml) significantly inhibited gray mold and blue mold rot of pears.The disease incidence of gray mold and blue mold of pears treated with the combinational treatment were 15.29%and 71.66%of that in the control,and the lesion diameter were 28.04%and 36.63%of that in the control respectively(P＜0.05).MeJA at 200μmol/l significantly reduced the number of B. cinerea and P.expansum in PDA and the germ tube length in PDB,whereas,it had no significant effect on the spore germination.The population of R.glutinis increased greatly by the presence of MeJA in the wounded sites.MeJA in combined with R. glutinis significantly inhibited natural infections and had no significant effect on quality parameters of nature pear fruits.4.In order to invest the biocontrol efficacy and its mechanism of C.laurentii reinforced by ozone to control gray mold of strawberries,the effect of antagonist, pathogens and fruits treated with ozone were studied.The ozone gas treatment at the concentration of 0.574μg/ml could significantly inhibit the gray mold rots incidence in strawberries.The combination of C.laurentii(1×10⁸ CFU/ml) with ozone(0.574μg/ml) significangtly reduced the disease incidence of gray mold from 70.37%to 29.63%.Ozone gas significantly inhibited the spore germination of B.cinerea in PDB. Ozone,C.laurentii and the combination of both increased the activity of PPO,POD, PAL,CAT,CHT and GHT in fruits,and reduced the activity of LOX.The combination of C.laurentii and ozone significantly inhibited the nature disease incidence and had no significant effect on quanlity of fruits.In conclusion,the biocontrol efficacy of biological antagonists(R.glutinis or C. laurentii) could be improved by use of SA,MeJA and ozone.