Plants host a complex microbiota inside or outside their tissues, and phyllosphere microorganisms can be influenced by environmental, nutritional and agronomic factors. Rare sugars are defined as monosaccharides with limited availability in nature and they are metabolised by only few certain microbial taxa. Among rare sugars, tagatose (TAG) is a low-calories sweetener that stimulates and inhibits beneficial and pathogenic bacteria in the human gut microbiota, respectively. Based on this differential effect on human-associated microorganisms, we investigated the effect of TAG treatments on the grapevine phyllosphere microorganisms to evaluate whether it can engineer the microbiota and modify the ratio between beneficial and pathogenic plant-associated microorganisms. TAG treatments changed the structure of the leaf microbiota and they successfully reduced leaf infections of downy mildew (caused by Plasmopara viticola) and powdery mildew (caused by Erysiphe necator) under field conditions. TAG increased the relative abundance of indigenous beneficial microorganisms, such as some potential biocontrol agents, which could partially contribute to disease control. The taxonomic composition of fungal and bacterial leaf populations differed according to grapevine locations, therefore TAG effects on the microbial structure were influenced by the composition of the originally residing microbiota. TAG is a promising biopesticide that could shift the balance of pathogenic and beneficial plant-associated microorganisms, suggesting selective nutritional/anti-nutritional properties for some specific taxa. More specifically, TAG displayed possible plant prebiotic effects on the phyllosphere microbiota and this mechanism of action could represent a novel strategy that can be further developed for sustainable plant protection.

植物在其组织内部或外部具有复杂的微生物群，并且叶环微生物可能会受到环境，营养和农艺因素的影响。稀有糖被定义为自然界中可用性有限的单糖，它们仅由某些微生物分类群代谢。在稀有糖中，塔格糖（TAG）是一种低热量甜味剂，分别刺激和抑制人类肠道微生物群中的有益细菌和致病细菌。基于这种对人类相关微生物的不同影响，我们调查了TAG处理对葡萄叶圈微生物的影响，以评估其是否可以改造微生物菌群，并改变有益和致病植物相关微生物之间的比例。纤毛虫（Plasmopara viticola）和白粉病（由Erysiphe necator引起））在野外条件下。TAG增加了本地有益微生物（例如某些潜在的生物防治剂）的相对丰度，这可能部分有助于疾病控制。真菌和细菌叶片种群的分类学组成因葡萄的位置而异，因此，TAG对微生物结构的影响受原始微生物群落组成的影响。TAG是一种有前途的生物农药，可以改变病原性和有益于植物的微生物的平衡，为某些特定的生物分类提供了选择性的营养/抗营养特性。进一步来说，