In Vitro Antagonistic Activity of <i>Trichoderma harzianum</i> against <i>Fusarium sudanense</i> Causing Seedling Blight and Seed Rot on Wheat

Abstract

<i>Fusarium sudanense</i> is a novel fungus recently isolated from asymptomatic samples of wheat grains in Argentina. The fungus caused symptoms of seedling blight and seed rot on wheat after artificial inoculations. It is known that the production of mycotoxins by pathogens belonging to the <i>Fusarium genus</i> is harmful to human and animal health. Moreover, the warm and humid conditions that are favorable for growth and mycotoxin production of these species put the Argentinian wheat production area at a high risk of mycotoxin contamination with this novel pathogen. The aim of this work was to evaluate the antagonistic effect of <i>Trichoderma harzianum</i> against <i>F. sudanense</i> under in vitro tests at different environmental conditions. Fungi were screened in dual culture at different water activities (αw) (0.995, 0.98, 0.95, and 0.90) and temperatures (25 and 15 °C). The growth rate of the fungi, interaction types, and dominance index were evaluated. Also, the interaction between <i>T. harzianum</i> and <i>F. sudanense</i> was examined by light and cryo-scanning microscopy. <i>T. harzianum</i> suppressed the growth of <i>F. sudanense</i> at 0.995, 0.98, and 0.95 αw at 25 °C and 0.995 and 0.98 αw at 15 °C. Macroscopic study revealed different interaction types between <i>F. sudanense</i> and <i>T. harzianum</i> on dual culture. Dominance on contact where the colonies of <i>T. harzianum</i> overgrew the pathogen was the most common interaction type determined. The competitive capacity of <i>T. harzianum</i> was diminished by decreasing the temperature and αw. At 0.95 αw and 15 °C, both fungi grew slowly, and interaction type "A" was assigned. Microscopic analysis from the interaction zone of dual cultures revealed an attachment of <i>T. harzianum</i> to the <i>F. sudanense hyphae</i>, penetration with or without formation of appressorium-like structures, coiling, plasmolysis, and a veil formation. According to our results, <i>T. harzianum</i> demonstrated capability to antagonize <i>F. sudanense</i> and could be a promising biocontrol agent.