Rhizospheric bacteria as potential biocontrol agents against Fusarium wilt and crown and root rot diseases in tomato

Abstract

The discovery of novel biocontrol agents requires the continuous scrutiny of native microorganisms to ensure that they will be useful on a regional scale. The goal of the present work was to discover novel antagonistic bacteria against Fusarium oxysporum ff. spp. lycopersici race 3 ( Fol R3) and radicis-lycopersici ( Forl ) causing Fusarium wilt disease and Fusarium crown and root rot of tomatoes, respectively. High-throughput liquid antagonism screening of 1,875 rhizospheric bacterial strains followed by dual confrontation assays in 96-well plates was used to select bacteria exhibiting > 50% fungal growth inhibition. In a second dual confrontation assay in 10-cm Petri dishes, bacteria showing > 20% Fol R3 or Forl growth inhibition were further screened using a blood hemolysis test. After discarding β-hemolytic bacteria, a seedling antagonistic assay was performed to select five potential antagonists. A phylogenetic analysis of 16S rRNA identified one strain as Acinetobacter calcoaceticus ( Ac DB3) and four strains as members of the genus Bacillus ( B. amyloliquefaciens Ba MA26, Bacillus siamensis Bsi DA2, B. subtilis Bs TA16 and B. thuringiensis Bt MB9). Greenhouse assays demonstrated that Bs TA16 and Ac DB3 were the most promising antagonists against Fol R3 and Forl , respectively. Pathogen biocontrol and growth promotion mechanisms used by these bacteria include the production of siderophores, biofilm, proteases, endoglucanases and indole acetic acid, and phosphate solubilization. These five bacteria exerted differential responses on pathogen control depending on the tomato hybrid, and on the growth stage of tomatoes. We report for the first time the use of an Acinetobacter calcoaceticus isolate ( Ac DB3) to control Forl in tomato under greenhouse conditions.

Quorum Quenching Strains Isolated from the Microbiota of Sea Anemones and Holothurians Attenuate Vibriocorallilyticus Virulence Factors and Reduce Mortality in Artemiasalina

“…Other strains of those genera with QQ activity have shown potential as biocontrol tools. For example, A. calcoaceticus reduced Fusarium oxysporum infection in tomato [ 91 ], and Acinetobacter sp. XN-10 reduced the pathogenicity of P. carotovorum subsp.…”

Biocontrol Effect of Bacillus subtilis YPS-32 on Potato Common Scab and Its Complete Genome Sequence Analysis

“…subtilis YPS-7 against S. scabies were determined by the plate confrontation test as previously described, with some modifications . This test was conducted on Petri plates (9 cm in diameter) containing YME medium.…”

“…The inhibition rates of different concentrations of B. subtilis YPS-32 and B. subtilis YPS-7 against S. scabies were determined by the plate confrontation test as previously described, with some modifications. 13 This test was conducted on Petri plates (9 cm in diameter) containing YME medium. A S. scabies mycelial plug (6 mm in diameter) was placed at the center of each Petri plate, and 50 μL of B. subtilis YPS-32 or B. subtilis YPS-7 suspension at different concentrations was applied at the edge, 2 cm from the center.…”

“…The plates were incubated at 28 °C for 24 h, and the inhibition rates of B. subtilis YPS-32 and B. subtilis YPS-7 were calculated as previously described. 13 ARTP Mutagenesis. About 10 μL of 10 5 −10 6 cfu/mL B. subtilis YPS-7 suspension grown to the logarithmic phase was spread on a sterilized steel plate and placed in a sterilized ARTP chamber for mutagenesis.…”

Isolation and identification of a new biocontrol bacteria against Salvia miltiorrhiza root rot and optimization of culture conditions for antifungal substance production using response surface methodology

“…According to the method reported by Khalil et al [19], the endophytic antagonistic bacteria isolated from S. miltiorrhiza were screened for their antagonistic activity against the target pathogen F. oxysporum using the dual plate confrontation assay method. A 5-mm puncher was used to punch holes on F. oxysporum plates cultured for 7 days.…”