Abstract
This study evaluated the effects and underlying mechanisms of different combinations of plant symbiotic microbes, comprising arbuscular mycorrhizal fungi (AMF), plant growth-promoting rhizobacteria (PGPR), and Trichoderma spp., on tomato Fusarium crown and root rot (TFCRR) resistance. A total of 54 treatments were applied in a greenhouse pot experiment to tomato (Solanum lycopersicum) seedlings inoculated with or without Funneliformis mosseae (Fm), Rhizophagus intraradices (Ri), Trichoderma virens l40012 (Tv), Trichoderma harzianum l40015 (Th), Bacillus subtilis PS1-3 (Bs), Pseudomonas fluorescens PS2-6 (Pf), and Fusarium oxysporum f. sp. radicis-lycopersici (Fo). The symbioses on the tomato root system were well developed, and the composite symbiont generated by AMF + Trichoderma spp. was observed for the first time. Compared with other treatments, Ri + Bs + Tv and Fm + Pf + Tv stimulated the greatest improvements in tomato growth and yield. The combination Ri + Pf + Th + Fo resulted in the strongest biocontrol effects on TFCRR, followed by the treatments Th + Pf + Fo and Ri + Th + Fo. Compared with the Fo treatment, most inoculation treatments improved photosynthetic performance and significantly increased defense enzyme activity in tomato plants, of which the treatment Ri + Pf + Th + Fo showed the highest enzyme activity. Metabolome analysis detected changes in a total of 1,266 metabolites. The number of up-regulated metabolites in tomato plants inoculated with Ri + Pf + Th and Ri + Pf + Th + Fo exceeded that of the Fo treatment, whereas the number of down-regulated metabolites showed the opposite trend. It is concluded that AMF + Trichoderma + PGPR is the most effective combination to promote resistance to TFCRR in tomato. The up-regulation and down-regulation of metabolites regulated by symbiotic microbial genes may be an important mechanism by which root symbiotic microorganisms promote plant growth, increase yield, and improve disease resistance.
Highlights
With the increase in prevalence of multiple cropping regimes and aggravation of obstacles to continuous cropping, soil-borne diseases increasingly restrict tomato (Solanum lycopersicum) production, especially under protected cultivation
The objective of the present study was to evaluate the effect of inoculation with arbuscular mycorrhizal fungi (AMF), Trichoderma spp., and plant growthpromoting rhizobacteria (PGPR), either alone or in combinations, on resistance to tomato Fusarium crown and root rot (TFCRR) and to explore the possible mechanisms of the biocontrol effects
Root Symbionts Formed With the Symbiotic Microbes
Summary
With the increase in prevalence of multiple cropping regimes and aggravation of obstacles to continuous cropping, soil-borne diseases increasingly restrict tomato (Solanum lycopersicum) production, especially under protected cultivation. Among such diseases, tomato Fusarium crown and root rot (TFCRR) has become a highly destructive soil-borne disease (Kucharek et al, 2000; Hibar et al, 2006; Cao et al, 2018; Li et al, 2018). Selection of resistant cultivars and grafting onto diseaseresistant rootstock are effective means of prevention (Thorpe and Jarvis, 1981) These methods and approaches have certain limitations. It is necessary to develop more efficient and time-saving preventive and control technologies
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