Abstract
Endophytic bacteria serve key roles in the maintenance of plant health and growth. Few studies to date, however, have explored the antagonistic and plant growth-promoting (PGP) properties of Prunus cerasifera endophytes. To that end, we isolated endophytic bacteria from P. cerasifera tissue samples and used a dual culture plate assay to screen these microbes for antagonistic activity against Verticillium dahliae, Botryosphaeria dothidea, Fusarium oxysporum, F. graminearum, and F. moniliforme. Of the 36 strains of isolated bacteria, four (strains P1, P10, P16, and P20) exhibited antagonistic effects against all five model pathogens, and the P10 strain exhibited the strongest antagonistic to five pathogens. This P10 strain was then characterized in-depth via phenotypic assessments, physiological analyses, and 16s rDNA sequencing, revealing it to be a strain of Bacillus subtilis. Application of a P10 cell suspension (1×108 CFU/mL) significantly enhanced the seed germination and seedling growth of tomato in a greenhouse setting. This P10 strain further significantly suppressed tomato Verticillium wilt with much lower disease incidence and disease index scores being observed following P10 treatment relative to untreated plants in pot-based experiments. Tomato plants that had been treated with strain P10 also enhanced defense-related enzymes, peroxidase, superoxide dismutase, and catalase activity upon V. dahliae challenge relative to plants that had not been treated with this endophytic bacterium. The results revealed that the P10 bacterial strain has potential value as a biocontrol agent for use in the prevention of tomato Verticillium wilt.
Highlights
IntroductionEndophytic bacteria and fungi are microbial species that asymptomatically colonize specific plants and that can regulate a range of host physiological responses
We isolated 36 strains of endophytic bacteria from P. cerasifera, with 11, 9, and 16 strains being isolated from the roots, stems, and leaves of these plants. The ability of these endophytes to antagonize the growth of five strains of pathogenic fungi (V. dahliae, B. dothidea, F. graminearum, F. oxysporum, and F. moniliforme) was assessed
Specific B. subtilis strains exhibiting a high degree of antagonistic activity towards phytopathogens represent ideal agents for the biocontrol of a range of fungal diseases (Chen et al, 2014; Shrestha et al, 2016; Sun et al, 2017), including fungal diseases such as wheat root rot caused by F. graminearum (Moussa et al, 2013), apple ring rot caused by B. dothidea (Fan et al, 2017), tomato gray mold and leaf mold caused by Botrytis cinerea and Cladosporium fulvum respectively (Wang et al, 2018), pea wilt disease caused by F. oxysporum (Khan et al, 2018), pepper seedling wilt disease and rice sheath blight caused by Rhizoctonia solani
Summary
Endophytic bacteria and fungi are microbial species that asymptomatically colonize specific plants and that can regulate a range of host physiological responses. These endophytes exhibit mutualistic relationships with their hosts such that plants provide these microbes with nutrients necessary for growth and survival, and these. The most commonly characterized endophytic bacteria are Bacillus species (Lilley et al, 1996; Viana et al, 2020), with B. subtilis being well known for its ability to promote plant growth (Poonguzhali et al, 2006) and to antagonize a range of plant pathogens, including Ceratocystis ulrni (Schreiber et al, 1988), Fusarium moniliforme (Hinton and Bacon, 1995), Xanthomonas oryzae (Lin et al, 2001), X. campestris pv. B. subtilis strains can be isolated from individual hosts and used to inoculate other plants in order to enhance their growth and pathogen resistance (Bacon and Hinton, 2002)
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