Discovery of Tropolone Stipitaldehyde as a Potential Agent for Controlling Phytophthora Blight and Its Action Mechanism Research

Abstract

The fermentation of endophytic <i>Nigrospora chinensis</i> GGY-3 resulted in the isolation of tropolone stipitaldehyde (<b>1</b>), which exhibited broad-spectrum inhibition activity against fungi and bacteria, especially against <i>Phytophthora capsici</i>, with an EC₅₀ value of 0.83 μg/mL and <i>Xanthomonas oryzae</i> pv. <i>oryzicola</i>, with a minimum inhibitory concentration value of 4.0 μg/mL. The in vitro and in vivo assays demonstrated that <b>1</b> had a significant protective effect on <i>P. capsici</i>. Furthermore, <b>1</b> inhibited the spore germination of <i>P. capsici</i> and damaged the plasma membrane structure. As observed by SEM and TEM, after exposure to <b>1</b>, mycelia exhibited swelling, shrunken, branch-increasing phenomena, cell wall and membrane damage, and disordered content. Transcriptome analysis revealed that <b>1</b> might affect starch and sucrose metabolism and fatty acid biosynthesis by suppressing the expression of genes relevant to cell wall synthetases and cell membrane-associated genes. These findings indicate that <b>1</b> may be a potential agrochemical fungicide for controlling phytophthora blight.