Data_Sheet_1_Antifungal Mechanism of Dipicolinic Acid and Its Efficacy for the Biocontrol of Pear Valsa Canker.pdf

Valsa pyri is a fatal canker pathogen that causes significant reduction of crop yield in pear orchards. V. pyri invades the trunk phloem, and is difficult to control by chemical treatment. In this work, it was found for the first time that Bacillus subtilis-produced dipicolinic acid (DPA) exhibits antifungal activity against different canker pathogens, including Alteraria alternata, Botryosphaeria dothidea, Rhizoctonia solani, and V. pyri. Growth inhibition of V. pyri was observed at less than 5 mM concentration (pH = 5.6). DPA showed the highest antifungal activity at acidic pH values and in the presence of bivalent metals, such as zinc(II), cobalt(II), and copper(II). Measurement of mRNA expression levels and scanning electron microscope (SEM) observations revealed that DPA causes V. pyri apoptosis via inhibition of chitin biosynthesis and subsequent cell lysis. Interestingly, DPA showed high stability in the pear bark and was able to cross the pear tree bark into the phloem, protecting the internal phases of the pear trunk. In preventive applications, DPA reduced the canker symptoms of V. pyri on Cuigan pear trees by 90%. Taken together, an efficient strategy for the management of V. pyri-caused canker disease was developed using a novel antifungal agent, DPA, with strong antifungal activity and particular diffusion properties.

梨生壳囊孢（Valsa pyri）是一种致死性溃疡病病原菌，可显著降低梨园的作物产量。该病原菌可侵染梨树树干韧皮部，且难以通过化学药剂进行防控。本研究首次发现，枯草芽孢杆菌（Bacillus subtilis）产生的吡啶二羧酸（dipicolinic acid, DPA）对多种溃疡病病原菌具有抗真菌活性，包括交链格孢（Alternaria alternata）、葡萄座腔菌（Botryosphaeria dothidea）、立枯丝核菌（Rhizoctonia solani）以及梨生壳囊孢（V. pyri）。在浓度低于5 mM、pH为5.6的条件下，即可观察到梨生壳囊孢的生长受到抑制。吡啶二羧酸在酸性pH环境及锌(II)、钴(II)、铜(II)等二价金属离子存在时，抗真菌活性最高。通过mRNA表达水平检测及扫描电子显微镜（scanning electron microscope, SEM）观察发现，吡啶二羧酸可通过抑制几丁质生物合成及后续的细胞裂解，诱导梨生壳囊孢发生凋亡。值得注意的是，吡啶二羧酸在梨树皮中具有较高稳定性，且可穿透梨树皮抵达韧皮部，对梨树树干内部组织起到保护作用。在预防性施用场景中，吡啶二羧酸可使翠冠梨树上由梨生壳囊孢引发的溃疡病症状减轻90%。综上，本研究开发了一种基于新型抗真菌剂吡啶二羧酸的高效防控策略，该药剂具备优异的抗真菌活性与独特的扩散性能，可用于防控梨生壳囊孢引发的溃疡病。