To evaluate the potential of a bacterial strain as a fungal disease control agent and plant growth promoter, its inhibitory effects on phytopathogens such as Bipolaris sorokiniana, Botrytis cinerea, Colletotrichum capsici, Fusarium graminearum, F. oxysporum, Neocosmospora rubicola, Rhizoctonia solani, and Verticillium dahliae were investigated. The results showed that the inhibitory rates in dual-culture and sterile filtrate assays against these eight phytopathogens ranged from 57% to 83% and from 36% to 92%. The strain was identified as Bacillus velezensis based on morphological and physiological characterization as well as phylogenetic analyses of 16S rRNA and the gyrase subunit A protein (gyrA) regions. The results demonstrated that B. velezensis was able to produce fungal cell-wall-degrading enzymes, namely, protease, cellulase, and β-1,3-glucanase, and the growth-promotion substances indole-3-acetic acid (IAA) and siderophore. Furthermore, B. velezensis BV01 had significant control effects on wheat root rot and pepper Fusarium wilt in a greenhouse. Potted growth-promotion experiments displayed that BV01 significantly increased the height, stem diameter, and aboveground fresh and dry weights of wheat and pepper. The results imply that B. velezensis BV01, a broad-spectrum biocontrol bacterium, is worth further investigation regarding its practical applications in agriculture.

Tomato late blight caused by Phytophthora infestans is a devastating disease, and current control of the disease relies heavily on chemical fungicides. Certain Trichoderma strains used as biocontrol fungi have shown superb efficacy against P. infestans and some other oomycete phytopathogens. In this study, T. paratroviride strain 8942 appeared to be effective in control of tomato late blight disease, reducing the necrosis degree of plant tissues, promoting callose deposition in tomato leaves, and increasing defense enzyme activities. RT-qPCR analysis showed that strain 8942 inhibited metabolism of salicylic acid and promoted metabolism of jasmonic acid at the early stage of colonization. In addition, root colonization of the strain significantly promoted tomato growth. Observations of rhizosphere soil properties showed that 8942 significantly increased the activities of urease, catalase, and protease, and its cell-free filtrates at low concentrations induced the accumulation of auxin in root tips. Transcriptomic data suggested the existence of a balance between biotrophic adaptation and biocontrol readiness during 8942’s interaction with tomato roots. Trichoderma paratroviride strain 8942 is promising and has potential for biological control of tomato late blight and plant growth promotion, as determined by integrated investigations of hormonal regulation, rhizosphere modulation, transcriptional reprogramming, etc.