Phenolic Compounds Accumulation and Cell Death Degree Induced by Fusaric Acid in Agroforestry Hosts Plants of Fusarium Species

The genus <i>Fusarium</i> comprises multiple species recognized as plant pathogens in both annual and perennial crops. Some phytopathogenic species of this genus can be transmitted by insect vectors, which introduce them into woody plant species of ecological and agroeconomic importance. Among these species, <i>Fusarium kuroshium</i> stands out, but studies are limited because it is a quarantine pathogen that requires special biosafety measures for its culture. This fungus produces fusaric acid (FA), a virulence factor that is widespread in <i>Fusarium</i> spp. To gain insight into the role of this phytotoxin in virulence, we exposed leaves of four woody host species (<i>Liquidambar styraciflua</i>, <i>Persea americana</i>, <i>Citrus sinensis</i>, and <i>Populus nigra</i>) of <i>F. kuroshium</i> to FA in vitro. The plant tissue exhibited varying degrees of cell death and physiological alterations, including a reduction in biomass, generation of reactive oxygen species (ROS), elevated electrolyte leakage, and loss of photosynthetic pigments. A chemical analysis demonstrated that the flavonoid and isoflavonoid pathways, in addition to linoleic and linolenic acid metabolism, were markedly affected by FA. Following the quantification of phenolic compounds in leaves, 11 metabolites were identified whose concentrations increased in response to FA stress. The findings of this study indicate that phenolic compounds play a significant role in the response to FA stress. Particularly, scopoletin has a protective effect on leaves of <i>Liquidambar styraciflua</i>.