Plant growth-promoting endophytic bacteria versus pathogenic infections: an example ofBacillus amyloliquefaciensRWL-1 andFusarium oxysporumf. sp.lycopersiciin tomato

Abstract

Fungal pathogenic attacks are one of the major threats to the growth and productivity of crop plants. Currently, instead of synthetic fungicides, the use of plant growth-promoting bacterial endophytes has been considered intriguingly eco-friendly in nature. Here, we aimed to investigate the in vitro and in vivo antagonistic approach by using seed-borne endophytic Bacillus amyloliquefaciens RWL-1 against pathogenic Fusarium oxysporum f. sp. lycopersici. The results revealed significant suppression of pathogenic fungal growth by Bacillus amyloliquefaciens in vitro. Further to this, we inoculated tomato plants with RWL-1 and F. oxysporum f. sp. lycopersici in the root zone. The results showed that the growth attributes and biomass were significantly enhanced by endophytic-inoculation during disease incidence as compared to F. oxysporum f. sp. lycopersici infected plants. Under pathogenic infection, the RWL-1-applied plants showed increased amino acid metabolism of cell wall related (e.g., aspartic acid, glutamic acid, serine (Ser), and proline (Pro)) as compared to diseased plants. In case of endogenous phytohormones, significantly lower amount of jasmonic acid (JA) and higher amount of salicylic acid (SA) contents was recorded in RWL-1-treated diseased plants. The phytohormones regulation in disease incidences might be correlated with the ability of RWL-1 to produce organic acids (e.g., succinic acid, acetic acid, propionic acid, and citric acid) during the inoculation and infection of tomato plants. The current findings suggest that RWL-1 inoculation promoted and rescued plant growth by modulating defense hormones and regulating amino acids. This suggests that bacterial endophytes could be used for possible control of F. oxysporum f. sp. lycopersici in an eco-friendly way.

Antifungal Activity of Bacillus Species Against Fusarium and Analysis of the Potential Mechanisms Used in Biocontrol

“…B. simplex 11 is an endophyte based on its isolation from dead root material (Kaplan et al, 2013), and other B. simplex strains are known to be endophytes in maize (Xia et al, 2015). In addition, endophytic bacteria have been shown to control Fusarium -induced plant diseases (Shahzad et al, 2017). …”

Co‐inoculation ofBacillussp. andPseudomonas putidaat different development stages acts as a biostimulant to promote growth, yield and nutrient uptake of tomato

“…Some species of Pseudomonas facilitate P solubilization for plants but also promote plant growth using different mechanisms (Vessey 2003;Otieno et al 2015). Bacillus amyloliquefaciens was reported as bio-control that improves soil health and disease resistance in plant and fruiting stages (Raza et al 2017;Shahzad et al 2017).…”

Role of salicylic acid from Pseudomonas aeruginosa PF23EPS+ in growth promotion of sunflower in saline soils infested with phytopathogen Macrophomina phaseolina

“…Earlier studies have reported that SA is involved in protecting plants under abiotic and biotic stresses including salinity (Amira and Qados 2015;Wang et al 2007;Horvath et al 2007;Dempsey and Klessig 2017). SA a metabolite reported commonly to be produced by pseudomonads (Mehran et al 2013) and has a role in induce systemic resistance (Ran et al 2005;Schuhegger et al 2006;Shahzad et al 2017). The positive role of bacterial EPS, as an elicitor, for the induction of systemic resistance against various phytopathogens of different crop species has been reported by Prashar et al (2013), Thenmozhi and Dinakar (2014).…”

“…Regulation of exo genes involved in EPS synthesis and carbon metabolism by SA has been reported earlier in diverse bacterial strains (Kunkel and Brooks 2002;Lamothe et al 2012;Yan et al 2014). Several workers also reported the role of EPS and SA as signal molecules (Zipfel 2009;Tewari and Arora 2013;Arora and Mishra 2016;Shahzad et al 2017). AHL synthase gene swrI produces quorum sensing molecule, C 6 HSL (N-hexanoyl l-homo-serine lactone), that induces SA production in Serratia liquefaciens (Sakhabutdinova et al 2003).…”