Isolation and characterization of rhizosphere bacteria for the biocontrol of the damping-off disease of tomatoes in Tunisia

Abstract

Fluorescent Pseudomonas spp., isolated from tomato and pepper plants rhizosphere soil, was evaluated in vitro as a potential antagonist of fungal pathogens. Pseudomonas strains were tested against the causal agents of tomatoes damping-off (Sclerotinia sclerotiorum), root rot (Fusarium solani), and causal agents of stem canker and leaf blight (Alternaria alternata). For this purpose, dual culture antagonism assays were carried out on 25% tryptic soy agar, King B medium and potato dextrose agar to determine the effect of the strains on mycelial growth of the pathogens. In addition, strains were screened for their ability to produce exoenzymes and siderophores. All the strains significantly inhibited Alternaria alternata, particularly in 25% TSA medium. Antagonistic effect on Sclerotinia sclerotiorum and Fusarium solani was greater on King B medium. Protease was produced by 30% of the strains, but no strain produced cellulase or chitinase. Finally, the selected Pseudomonas strain, Psf5, was evaluated on tomato seedling development and as a potential candidate for controlling tomato damping-off caused by Sclerotinia sclerotiorum, under growth chamber conditions. In vivo studies resulted in significant increases in plant stand as well as in root dry weight. Psf5 was able to establish and survive in tomato plants rhizosphere after 40 days following the planting of bacterized seeds.

Biocontrol of tomato plant diseases caused by Fusarium solani using a new isolated Aspergillus tubingensis CTM 507 glucose oxidase

“…The pH was adjusted to 5.0 and the medium was supplemented with chloramphenicol (0.1 g/L) to inhibit bacterial growth; the solid screening medium used for the preliminary selection of GOD producing strains, contains 10 g/L of glucose, 6 g/L of NaNO 3 , 0.5 g/L of KCl, 0.5 g/L of MgSO 4 Á7H 2 O, 1.5 g/L of KH 2 PO 4 with traces of CuSO 4 , ZnSO 4 , MnCl 2 and FeSO 4 , 20 g of agar and 2.5 mM o-dianisidine [21]; the liquid medium used for GOD production contains 10 g/L of glucose, 1 g/L of peptone from casein, 5 g/L of yeast extract, 6 g/L of NaNO 3 , 0.5 g/L of KCl, 0.5 g/L of MgSO 4 Á7H 2 O, 1.5 g/L of KH 2 PO 4 with traces of CuSO 4 , ZnSO 4 , MnCl 2 and FeSO 4 [21]; Potato Dextrose Agar (PDA, Oxoid, Johannesburg) was used for pre-growing the new isolated fungi GOD production and the pathogen F. solani [24]; the tryptone salt medium utilized for the storage of the pathogen F. solani contains 1 g/L of tryptone, 8.5 g/L of NaCl, 1% of Tween 20, and 15% of glycerol [24].…”

“…The pathogen F. solani was isolated and then identified by the Olive Tree Institute of Sfax, as described by Hammami et al [24] and kindly provided by Dr. Mohamed Ali Triki. The fungus was isolated from tomato plants exhibiting symptoms of tomato damping-off.…”

Assessment of plant growth promoting activities and abiotic stress tolerance of Azotobacter chroococcum strains for a potential use in sustainable agriculture

“…Antimicrobial antagonism was evaluated using the dual culture method described by Hammami et al (2013) were cultivated in malt extract agar (Oxoid, Milan, Italy) at 28 °C. Conidia were harvested from the surface of plates by flooding the 10-day-old cultures with 9 ml of sterilized distilled water and gently scraping with a sterilized glass rod.…”

Isolation, Identification and Characterization of <i>Bacillus subtilis</i> CF-3, a Bacterium from Fermented Bean Curd for Controlling Postharvest Diseases of Peach Fruit

“…Biocontrol bacteria isolated from food, plant roots, soil, etc are much safer than from other sources (Hammami et al, 2013 andMitter et al, 2013). Fermented bean curd, the most typical traditional Chinese fermented soy food, is made by microbial fermentation beginning with soybean as raw material and is favored by many people for its unique taste and nutritional value (Juan et al, 2014).…”