Epiphytic yeasts were isolated from different cultivars of apples and lemons and identified by a combination of PCR‐RFLP of 5.8S rRNA region and sequencing of D1/D2 domain of the 26S rRNA gene. Among 69 isolates, Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 strains showed the greatest antagonistic activity against two significant apple and lemon postharvest pathogens, Penicillium expansum DSM62841 (blue mold) and Penicillium digitatum DSM2750 (green mold), after preliminary screening. Yeasts were applied as single and mixed cultures with two different cell concentrations of 10⁶ and 10⁸ cells/ml in the present study. It was determined that antagonistic activity of two yeast strains studied emerged with a combination of several mechanisms of action including competition for space and nutrients, production of volatile organic compounds (VOCs), secretion of extracellular lytic enzymes and inhibition of fungal spore germination. The highest inhibition of mycelial growth on P. expansum DSM62841 and P. digitatum DSM2750 (83.4% and 74.7%, respectively) was achieved by utilization of single culture of A. pullulans GE17. Otherwise, the application of mixed culture at the ratio of 10⁸ cells/ml inhibited spore germination of both pathogens from 86% to 95%. Results of this study suggest that an increase in yeast cell concentrations positively affected their biocontrol activity against blue and green molds. According to the results, employing single culture of M. guilliermondii KL3 did not exhibit effective antagonistic activity against blue and green molds. However, utilization of A. pullulans GE17 alone and mixed culture showed succesfull controlling against both P. expansum DSM62841 and P. digitatum DSM2750.

中文翻译：

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Aureobasidium pullulans GE17和Meyerozyma guilliermondii KL3对指状青霉DSM2750和Penicillium expansum DSM62841引起的采后病害的生防能力和作用机制。

从苹果和柠檬的不同栽培品种中分离出附生酵母，并通过 5.8S rRNA 区域的 PCR-RFLP 和 26S rRNA 基因的 D1/D2 结构域的测序相结合进行鉴定。初步筛选后，在 69 株分离物中，Aureobasidium pullulans GE17 和Meyerozyma guilliermondii KL3 菌株对两种重要的苹果和柠檬采后病原体，Penicillium expansum DSM62841（蓝霉）和Penicillium digitatum DSM2750（绿霉）表现出最大的拮抗活性。酵母作为单一和混合培养物应用，具有两种不同的细胞浓度 10 ⁶和 10 ⁸本研究中的细胞/毫升。确定所研究的两种酵母菌株的拮抗活性是通过多种作用机制的组合出现的，包括空间和营养竞争、挥发性有机化合物 (VOC) 的产生、细胞外裂解酶的分泌和真菌孢子萌发的抑制。通过使用A. pullulans GE17的单一培养物实现了对P. expansum DSM62841 和P. digitatum DSM2750菌丝生长的最高抑制（分别为 83.4% 和 74.7%）。否则，按 10 ⁸的比例混合培养细胞/毫升抑制了两种病原体的孢子萌发，从 86% 到 95%。这项研究的结果表明，酵母细胞浓度的增加对其对蓝色和绿色霉菌的生物防治活性产生了积极影响。根据结果​​，采用单一培养物M. guilliermondii KL3 对蓝霉菌和绿霉菌没有表现出有效的拮抗活性。然而，单独使用A. pullulans GE17 和混合培养显示成功控制了P. expansum DSM62841 和P. digitatum DSM2750。