Study On Inhibition Of The Antagonistic Yeast On Gray Mold Of Postharvest Tomato Fruit

Tomato mold is one of the most important diseases caused by Botrytis cinerea.Antagonistic yeasts have shown great potential as an alternative to synthetic fungicides for the control of postharvest decay of tomato fruits.Unfortunately,the biocontrol potential of the antagonistic yeast strain KD-16J in suppression of Botrytis cinarea of tomato has not been assessed so far.Thus,the purpose of this study was to screen a new and efficient antagonistic yeast,studying its biological characteristics and inhibition mechanisn,testing its prevention and treatment of postharvest dieases of tomato fruit.The results achieved are summarized below:1.A antagonistic yeast isolate named KD-16J,from the tomato fruit with in vitro and in vivo methods.It showed high ability of inhibiting the disease of Botrytis cinerea.This strain was preliminarily identified as Pichia membranifaciens possiblely based on the similarity analysis of its morphologies,physiological-biochemical characteristics and 26S rDNA D1/D2 domain sequence.2.In vitro experiment,The obvious inhibiting effects of Botrytis cinerea on the mycelium growth,colony extension and spore germination by the antagonistic yeast strain KD-16J.The concentration of 109 CFU/mL of the antagonistic yeast strain KD-16J was treated of grey mould inhibition rate was 85.53%and the spore germination rate is as high as 100%.The results demonstrated that the disease incidence for the treatments of autoclaved cell culture and culture filtrate of the antagonistic yeast strain KD-16J was effctive in preventing the decay.Filtrate to deal with the inhibition rate of 14.67%higher than that of heat killing fluid,and is far lower than the yeast slurry treatment.we found the antagonistic yeast could be absorbed on the pathogen spores and hypha under a microscope and a scanning electron microscope.And the Botrytis cinerea can induced the activity of chitinase and β-1,3-glucanase increased in the culture medium of the antagonistic yeast strain KD-16J.All of the above results indicated that the antagonistic yeast strain KD-16J produce an antifungal substance,meanwhile,competition for nutrients and space on wounds appeared to play a role in the activity of biocontrol and it might be one of the mechanisms.And we can offer that parasitic role is existence between the antagonistic yeast strain KD-16J and Botrytis cinerea.3.By in vivo,tomato fruit treated with the antagonistic yeast strain KD-16J showed lower disease incidence and smaller lesion diameters caused by Botrytis cinerea,sprayed treatment by cell suspension of the antagonistic yeast strain KD-16J reduced the natural incidence rate of tomato fruits to the end of the storage is only 16.67%,obvious effect.The biocontrol efficacy of the antagonistic yeast strain KD-16J was related with different application time of the yeast,spraying processing time earlier,the better control effect,compared to the 93.64%incidence of yeast the incidence of early 36 h processing is only 29.12%.The antagonistic yeast strain KD-16J could acclimatize itself to the environment of tomato fruit wounds and occupy the living space quickly at room temperature,3 days increased 239.5 times than the initial value.In addition,the fruit inoculated with the antagonistic yeast strain KD-16J changed the expression of activities of peroxidase(POD),phenylalanine ammonia-lyase(PAL),chitinase(CHI)and β-1,3-glucanase,all of which were correlated with the onset of induced resistance.This result suggested that tomato fruit was capable of responding to the yeast the antagonistic yeast strain KD-16J,which could activate defensive enzymes,especially the PAL activity peak compared with the control group increased by 94.37%,there by induced host disease resistance.This might be also one of the mechanisms.4.The effect of the antagonistic yeast strain KD-16J on the quality of postharvest tomato was also studied.It reduced the incidence,inhibited the spot expanding,delayed fruit softening and sweetness changes,the biggest hardness difference of 9.3 kg/cm2,kepted the titratable acid content and ascorbic acid content,delayed respiratory peak of 1.5 days increased the total phenolic,which conducive to improve taste and good flavor.