Trichoderma asperellum empowers tomato plants and suppresses Fusarium oxysporum through priming responses

Abstract

Plant-associated microbes play crucial roles in plant health and promote growth under stress. Tomato (<i>Solanum lycopersicum</i>) is one of the strategic crops grown throughout Egypt and is a widely grown vegetable worldwide. However, plant disease severely affects tomato production. The post-harvest disease (<i>Fusarium</i> wilt disease) affects food security globally, especially in the tomato fields. Thus, an alternative effective and economical biological treatment to the disease was recently established using <i>Trichoderma asperellum</i>. However, the role of rhizosphere microbiota in the resistance of tomato plants against soil-borne <i>Fusarium</i> wilt disease (FWD) remains unclear. In the current study, a dual culture assay of <i>T. asperellum</i> against various phytopathogens (e.g., <i>Fusarium oxysporum</i>, <i>F. solani</i>, <i>Alternaria alternata</i>, <i>Rhizoctonia solani</i>, and <i>F. graminerarum</i>) was performed <i>in vitro</i>. Interestingly, <i>T. asperellum</i> exhibited the highest mycelial inhibition rate (53.24%) against <i>F. oxysporum</i>. In addition, 30% free cell filtrate of <i>T. asperellum</i> inhibited <i>F. oxysporum</i> by 59.39%. Various underlying mechanisms were studied to explore the antifungal activity against <i>F</i>. <i>oxysporum</i>, such as chitinase activity, analysis of bioactive compounds by gas chromatography-mass spectrometry (GC-MS), and assessment of fungal secondary metabolites against <i>F. oxysporum</i> mycotoxins in tomato fruits. Additionally, the plant growth-promoting traits of <i>T. asperellum</i> were studied (e.g., IAA production, Phosphate solubilization), and the impact on tomato seeds germination. Scanning electron microscopy, plant root sections, and confocal microscopy were used to show the mobility of the fungal endophyte activity to promote tomato root growth compared with untreated tomato root. <i>T. asperellum</i> enhanced the growth of tomato seeds and controlled the wilt disease caused by the phytopathogen <i>F. oxysporum</i> by enhancing the number of leaves as well as shoot and root length (cm) and fresh and dry weights (g). Furthermore, <i>Trichoderma</i> extract protects tomato fruits from post-harvest infection by <i>F. oxysporum</i>. Taking together, <i>T. asperellum</i> represents a safe and effective controlling agent against <i>Fusarium</i> infection of tomato plants.