Soil inoculation of Trichoderma asperellum M45a regulates rhizosphere microbes and triggers watermelon resistance to Fusarium wilt

Abstract

<jats:title>Abstract</jats:title> <jats:p>Fusarium wilt (FW) caused by <jats:italic>Fusarium oxysporum</jats:italic> f. sp. <jats:italic>niveum</jats:italic> (FON) is a soil-borne disease that seriously limits watermelon production. In the present study, the <jats:italic>Trichoderma asperellum</jats:italic> (<jats:italic>T. asperellum</jats:italic>) M45a was shown to be an effective biocontrol agent against Fusarium wilt (FW). In a pot experiment, the application of 10<jats:sup>5</jats:sup> cfu/g of <jats:italic>T. asperellum</jats:italic> M45a granules had better control effect on FW at the blooming period (up to 67.44%) from soils subjected to five years of continuous cropping with watermelon, while the average length of watermelon vine was also significantly improved(P &lt; 0.05). Additionally, the acid phosphatase (ACP), cellulase (CL), catalase (CAT) and sucrase (SC) activities in the M45a-inoculation group were significantly higher than in the control (CK) group, and the soil nutrients (total N, NO3-N, and available P) transformation was significantly increased. Moreover, <jats:italic>T. asperellum</jats:italic> M45a inoculation reduced fungal diversity and increased bacterial diversity, especially enhancing the relative abundance of PGPR (plant growth promoting rhizobacteria), such as <jats:italic>Trichoderma, Sphingomonas</jats:italic>, <jats:italic>Pseudomonas</jats:italic>, <jats:italic>Actinomadura</jats:italic> and <jats:italic>Rhodanobacter</jats:italic>. Through functional prediction, the relative abundance of Ectomycorrhizal, Endophyte, Animal pathotroph and saprotroph in fungal community was determined to be significantly lower than observed in the M45a-treated soil. Correlation analysis revealed that <jats:italic>Sphingomonas</jats:italic>, <jats:italic>Pseudomonas</jats:italic> and <jats:italic>Trichoderma</jats:italic> had the most differences in microorganisms abundance, positively correlated with ACP, CL, CAT and SC. These findings will provide ecological fungicide advice for microecological control of FW in continuous cropping watermelon.</jats:p>

Changes in the Density and Composition of Rhizosphere Pathogenic Fusarium and Beneficial Trichoderma Contributing to Reduced Root Rot of Intercropped Soybean

“…Since 1932, T. lignorum was rstly reported to have antagonistic effect on Rhizoctonia solani (Wending 1932), many Trichoderma species such as T. harzianum, T. viren, T. asperellum, T. hamatum, T. longibrachiatum and T. koningii, have successively been identi ed as antagonistic fungi against plant pathogens (Harman et al 2004;Izquierdo-García et al 2020), especially soil-borne pathogenic fungi (Anees et al 2010;Lynch et al 1991;Lahlali and Hijri 2010;Li et al 2018). For example, T. harzianum and T. asperellum are effective biological control agents against F. oxysporum causing watermelon wilt (Zhang et al 2020), and T. asperellum isolates signi cantly suppresses Fusarium tomato wilt (Cotxarrera et al 2002). Some Trichoderma strains can confer biocontrol either directly by interacting with pathogens via re-parasitism, or by competition for nutrients or root niches, while other strains establish robust and durable colonization of root surfaces and penetrate into the epidermal cells to indirectly induce host resistance mechanism and enhance root growth (Harman et al 2004;Hermosa et al 2012).…”