Screening, Identification Of An Antagonistic Yeast And Its Effect On Quality Of Postharvest Grape During Cold Storage Periode

Antagonistic yeasts have shown great potential as an alternative to synthetic fungicides for the control of postharvest decay of fruits and vegetables. Unfortunately, at present, the effectiveness and stability of antagonistic yeasts have not been reached a sufficient control level when compared with the synthetic fungicides. Thus, the purpose of this study was to screen a new and efficient antagonistic yeast, studying its biological characteristics, testing its prevention and treatment of postharvest dieases of fruit and vegetables. Some conclusions were drawn as follows:1. Eighty-five antagonistic yeasts were selected from the strawberry fruits, wounds, leaves and rhizosphere soil in Nanjing Maqun. A yeast isolate named CM2, from the strawberry fruits with in vitro and in vivo methods. It showed high ability of inhibiting the gray mould (B. cinerea) disease.2. This strain was preliminarily identified as Hanseniaspora uvarum based on the similarity analysis of its morphologiels, physiological-biochemical characteristics and26S rDNA D1/D2domain sequence.3. On growth curve test, CM2entered logarithmic phase after10hours and stable growth phase after18h, at28℃in the potato dextrose broth(PDB). The culture and conditions of the yeast strain CM2were optimized. Results showed that the optimum medium was PDB and the best carbon source was glucose. The optimal culture conditions were that:the inoculum lever was10%(v/v), the temperature was24℃, the initial pH7,25ml in250ml flasks, and the culture time was20h.4. Pretreatment with different concentrations of CM2could decrease the incidence of rot on postharvest grapes after inoculation with pathogenic fungi B. cinerea. The result showed that the higher concentration of CM2, the inhibition effect on the gray mould disease is better. The best inhibition concentration of CM2is1×108cfu-mL-1which could decrease the incidence of rot to37.6%, compared with rot only inoculating with pathogenic fungi.2mmol-L-1salicylic acid or2%sodium bicarbonate in combination with1×108cfu-mL-1CM2could decrease the incidence of rot to9%and10%on postharvest grapes after inoculation with pathogenic fungi B. cinerea, compared with rot only inoculating with CM2. The result showed that salicylic acid or sodium bicarbonate could improve the ability of CM2.5. Postharvest Kyoho treated with1×108cfu-mL-1CM2, CM2in combination with2mmol-L-1salicylic acid and2%sodium bicarbonate were stored at1℃(±1℃) with RH90～95%, the results showed that the best treatment was CM2in combination with2%sodium bicarbonate, next was in combination with2mmol-L-1salicylic acid. These treatments had little effect on soluble solids and vitamin C, but could significantly reduce the rotting rate, weightless and fell grain rate, maintain fruit luster, hardness, springiness cohesiveness, gumminess, chewiness resilience, the content of titratable acid, protein and reducing sugar, extend the storage life.These results laid a solid foundation to use the yeast CM2to control postharvest diseases of fruits and vegetables.