Food sciences |
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Classification and identification of yeast strain A822 and its inhibitory effect on Rhizopus stolonifer |
ZHOU Xiaohong#, YAN Dong#, LU Zhaoxin, L Fengxia, SHEN Chang, BIE Xiaomei* |
(College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, China
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Abstract In recent years, with the increase of peach cultivation area and yield, the techniques for the peach postharvest disease control need to be improved. Since the 1980s, due to a variety of advantages, such as safety, effectiveness and without causing antibiotics resistance, biological control has become more and more important for fruits and vegetables postharvest preservation. Although many kinds of biological control agents have been developed, antagonism yeasts still have wide application prospects because of their convenient use. This study aimed at systematic classification and identification of the yeast strain A822 and studied the antagonism effect on peach soft rot diseases Rhizopus stolonifer. To study the inhibitory effect of strain A822 on R. stolonifer, four different experiments were designed, including the antifungal test on plates, the mixed strains culture experiments, the antibacterial test using fermentation broth and inhibitory studies on peach fruit in vivo. Regarding to classification and identification of strain A822, we used general classification methods such as observation of the yeasts morphology, and characterization of physiology and biochemistry, supplemented with molecular biology methods to analyze 26S rDNA sequence. First of all, using four different antifungal experiments stepbystep demonstrated the obvious inhibitory effect of yeast A822 on R. stolonifer. The inhibitory test of yeast A822 on plates showed the notably antagonistic action on R. stolonifer; the mixed strains culture experiments indicated the inhibitory effect of yeast A822 on R. stolonifer growth and there is obviously positive correlation with concentration of yeast A822; the suppressive test of yeast A822 fermentation broth demonstrated that there was no antifungal substance secreted outside yeast A822 cell, and further investigation results showed that the inhibitory action was achieved through nutritional competition and spatial competition between strain A822 and R. stolonifer, rather than yeast A822 producing any antifungal substances to inhibit the growth of R. stolonifer; In vivo studies showed that the 1×108 cfu/mL concentration of yeast A822 has a significant inhibitory effect on peach fruits which were inoculated with the 1×105 spores/mL concentration of R. stolonifer. Secondly, through general classification methods including observation of the yeasts morphology, and characterization of physiology and biochemistry, it was found that the characteristics of the strain A822 was closest to Pichia sp. Furthermore, molecular methods was used to analyze the 26S rDNA sequence of strain A822, and by sequence comparison in GenBank, the antagonistic yeast A822 was ultimately determined as Pichia anomala. As safe and effective antagonistic fungi, yeasts have been highly concerned, researchers have been discovered many yeast species with biocontrol effect. However, at present there is no report that P. anomala had antagonistic effect on R. stolonifer. This study firstly identified that P. anomala A822 had an inhibitory effect on R. stolonifer, and its inhibitory mechanism was clarified. Based on the above results, we concluded that P. anomala A822 significantly inhibited R. stolonifer, therefore it has an important application potential in biological control and post harvest preservation of fruit and vegetable.
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Published: 20 January 2013
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酵母菌A82-2的分类鉴定及对桃软腐病菌的抑菌效果研究
对1株具有抗桃软腐病菌的酵母菌A82-2进行了系统分类鉴定。通过4种不同的抑菌实验研究该酵母菌对桃软腐病菌(Rhizopus stolonifer)的拮抗作用:平板抑菌实验表明菌株A82-2对R. stolonifer为拮抗阳性;菌株混合培养实验说明菌株A82-2对R. stolonifer抑菌效果明显,且与菌株A82-2菌悬液的含菌量呈正相关;发酵液抑菌实验表明菌株A82-2并没有向胞外分泌抑菌活性物质,说明菌株A82-2不是通过产生抑菌物质对R. stolonifer产生抑制作用,而是通过菌株之间的营养竞争和空间竞争产生拮抗作用;活体研究表明:1×108 cfu/mL菌株A822,对接种了1×105个孢子/mL桃软腐病菌的桃果实具有显著的抑制作用。采用形态特征观察和生理生化特性分析对该酵母进行了传统分类鉴定,进一步利用分子生物学方法对其26S rDNA序列进行分析,确定该拮抗酵母菌为异常毕赤酵母(Pichia anomala),该菌在果蔬病害的生物防治和防腐保鲜方面具有很高的应用潜力。
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