AUTHOR=Bandara Ananda Y. , Kang Seogchan 

TITLE=Trichoderma application methods differentially affect the tomato growth, rhizomicrobiome, and rhizosphere soil suppressiveness against Fusarium oxysporum

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1366690

DOI=10.3389/fmicb.2024.1366690

ISSN=1664-302X

ABSTRACT=<p><italic>Trichoderma</italic> spp. are widely used to enhance crop growth and suppress diverse diseases. However, inconsistent field efficacy remains a major barrier to their use as a reliable alternative to synthetic pesticides. Various strategies have been investigated to enhance the robustness of their application. Here, we evaluated how <italic>T. virens</italic> application methods (pre-, at-, and post-transplant) affect the growth of two tomato varieties and their rhizosphere fungal and bacterial communities. Although the greatest rhizosphere abundance of <italic>T. virens</italic> was observed in the post-transplant application, the at-transplant application promoted tomato growth the most, indicating that greater rhizosphere abundance does not necessarily result in better tomato growth. None of the application methods significantly altered the global rhizosphere fungal and bacterial communities of the tested varieties. Changes in specific microbial genera and guilds may underpin the enhanced tomato growth. We also investigated whether the resulting microbiome changes affect the mycelial growth and conidial germination of <italic>Fusarium oxysporum</italic> f. sp. <italic>lycopersici</italic> and <italic>F. oxysporum</italic> f. sp. <italic>radicis-lycopersici</italic>, soilborne fungal pathogens of tomato, upon exposure to volatile compounds emitted by culturable rhizosphere microbes and metabolites extracted from the rhizosphere soils after <italic>Trichoderma</italic> treatments. Volatile compounds produced by cultured rhizosphere microbes after the at-transplant application suppressed the mycelial growth of both pathogens better than those after the other treatments. Similarly, water-soluble metabolites extracted from the rhizosphere soil samples after the at-transplant application most effectively suppressed the germination rate of <italic>F. oxysporum</italic> spores. Overall, our results suggest that the at-transplant application is most advantageous for promoting the growth of the tested tomato varieties and building soil suppressiveness against the tested fusaria. However, further studies are needed before applying this method to support tomato production. We discuss critical future questions.</p>