title: 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 40days following the planting of bacterized seeds.
authors.affiliation: Unité de recherche protection des plantes cultivées et environnement, Institut de l'olivier, BP 1087, Sfax, Tunisia.
authors.forename: Inés
authors.initials: I
authors.lastname: Hammami
authors.forename: Anis
authors.initials: A
authors.lastname: Ben Hsouna
authors.forename: Naceur
authors.initials: N
authors.lastname: Hamdi
authors.forename: Radhouane
authors.initials: R
authors.lastname: Gdoura
authors.forename: Mohamed Ali
authors.initials: MA
authors.lastname: Triki
mesh_terms: D000528:Alternaria / Q000502:physiology; D001203:Ascomycota / Q000502:physiology; D061046:Biological Control Agents; D002688:Chitinases / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics; D005670:Fusarium; D007210:Indoleacetic Acids / Q000378:metabolism; D018551:Solanum lycopersicum / Q000382:microbiology*; D025282:Mycelium / Q000254:growth & development; D010572:Pest Control, Biological / Q000379:methods*; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000254:growth & development / Q000382:microbiology; D011549:Pseudomonas / Q000502:physiology; D058441:Rhizosphere; D012639:Seeds / Q000382:microbiology; D017262:Siderophores / Q000378:metabolism; D014416:Tunisia
chemical_list: D061046:Biological Control Agents; D004271:DNA, Fungal; D007210:Indoleacetic Acids; D017262:Siderophores; C030737:indoleacetic acid; D002688:Chitinases
keywords: Antagonistic bacteria; BCAs; Biological control agent; Damping-off; Fluorescent Pseudomonas spp.; IAA; Indole-3-acetic acid; KB; King B medium; PDA; PGPR; Phytopathogenic fungi; Plant growth-promoting rhizobacteria; Potato dextrose agar; TSA; Tomato; Tryptic soy agar