Cacao plantations from South America have been afflicted with the severe fungal disease known as Witches’ Broom Disease (WBD), caused by the basidiomycete Moniliophthora perniciosa. Yeasts are increasingly recognized as good fungal biocides, although their application is still mostly restricted to the postharvest control of plant and fruit decay. Their possible utilization in the field, in a preharvest phase, is nevertheless promising, particularly if the strains are locally adapted and evolved and if they belong to species considered safe for man and the environment. In this work, a group of yeast strains originating from sugarcane-based fermentative processes in Brazil, the cacao-producing country where the disease is most severe, were tested for their ability to antagonize M. perniciosa in vitro. Wickerhamomyces anomalus LBCM1105 and Saccharomyces cerevisiae strains LBCM1112 from spontaneous fermentations used to produce cachaça, and PE2 widely used in Brazil in the industrial production of bioethanol, efficiently antagonized six strains of M. perniciosa, originating from several South American countries. The two fastest growing fungal strains, both originating from Brazil, were further used to assess the mechanisms underlying the yeasts’ antagonism. Yeasts were able to inhibit fungal growth and kill the fungus at three different temperatures, under starvation, at different culture stages, or using an inoculum from old yeast cultures. Moreover, SEM analysis revealed that W. anomalus and S. cerevisiae PE2 cluster and adhere to the hyphae, push their surface, and fuse to them, ultimately draining the cells. This behavior concurs with that classified as necrotrophic parasitism/mycoparasitism. In particular, W. anomalus within the adhered clusters appear to be ligated to each other through roundish groups of fimbriae-like structures filled with bundles of microtubule-sized formations, which appear to close after cells detach, leaving a scar. SEM also revealed the formation of tube-like structures apparently connecting yeast to hypha. This evidence suggests W. anomalus cells form a network of yeast cells connecting with each other and with hyphae, supporting a possible cooperative collective killing and feeding strategy. The present results provide an initial step toward the formulation of a new eco-friendly and effective alternative for controlling cacao WBD using live yeast biocides.

来自南美洲的可可种植园遭受了严重的真菌病，称为 女巫的扫帚病 (WBD)，由担子菌引起 念珠菌. 酵母越来越多地被认为是良好的真菌杀虫剂，尽管它们的应用仍然主要限于植物和果实腐烂的收获后控制。然而，它们在收获前阶段在田间的可能利用是有希望的，特别是如果这些菌株在当地适应和进化，并且它们属于被认为对人类和环境安全的物种。在这项工作中，测试了一组源自巴西（该病最严重的可可生产国）以甘蔗为基础的发酵过程的酵母菌株的拮抗能力。M. perniciosa 体外. 异常柳条菌 LBCM1105 和 酿酒酵母 自发发酵菌株 LBCM1112 用于生产 卡查萨和PE2在巴西广泛用于生物乙醇的工业化生产，高效拮抗6株 鼠尾草，起源于几个南美国家。两种生长最快的真菌菌株均来自巴西，进一步用于评估酵母拮抗作用的潜在机制。酵母能够在三种不同的温度、饥饿、不同的培养阶段或使用来自旧酵母培养物的接种物来抑制真菌生长并杀死真菌。此外，SEM 分析表明，W. 异常 和 酿酒酵母PE2 聚集并粘附在菌丝上，推动它们的表面，并与它们融合，最终排出细胞。这种行为与归类为坏死性寄生/真菌寄生的行为一致。特别是，W. 异常在粘附的簇内，似乎通过圆形的伞状结构群相互连接起来，这些结构中充满了微管大小的结构束，这些结构在细胞分离后似乎闭合，留下了疤痕。SEM 还揭示了明显将酵母与菌丝连接起来的管状结构的形成。这个证据表明W. 异常细胞形成酵母细胞网络，相互连接并与菌丝连接，支持可能的合作集体杀戮和喂养策略。目前的结果为制定使用活酵母杀菌剂控制可可 WBD 的新型环保且有效的替代方案迈出了第一步。