Efficacy of olive mill waste water and its derivatives in the suppression of crown gall disease of bitter almond

Abstract

Olive mill waste water (OMW) and some of its indigenous bacterial strains were tested in vitro and in planta for their efficacy against crown gall disease caused by Agrobacterium tumefaciens. OMW and polyphenols displayed a high level of antibacterial activity, however the volatile fraction was less efficient as only a bacteriostatic effect was observed. In pot experiments, the percentage of bitter almond rootstock showing symptoms of crown gall was significantly reduced with the dosage rate of OMW 1% as compared to the control (highly natural infected soil treated with water). Five indigenous bacterial strains isolated from OMW exhibited an antagonistic effect against the bacterium. Based on the gene 16S rRNA sequence analysis, one isolate showed 99.2% similarity to known sequences of Bacillus subtilis, one isolate demonstrated high percentage similarities (99.3%) to the genera Bacillus pumilis, and two isolates were associated with Stenotrophomonas maltophilia and Pseudomonas putida 100% and 99.6% similarities respectively. Among these bacteria, the strain B1 proved efficient against the soil borne pathogen in vitro and pot experiments. Our study in controlled conditions suggested that the addition of OMW to soil exerts significant disease suppressiveness against A. tumefaciens.

The Microbiology of Olive Mill Wastes

“…Bacterial strains related to the genus Bacillus and the species Burkholderia caryophylli and Pseudomonas fluorescens induced in planta disease suppressiveness against Fusarium and/or Rhizoctonia damping-off of tomato [130]. Moreover, bacterial strains, which were isolated from OMW and related to the species Bacillus subtilis , B. pumilis , Pseudomonas putida, and Stenotrophomonas maltophilia , exerted in planta antimicrobial activity against Agrobacterium tumefaciens [135]. Serratia marcescens strain BR2.1 is a biocontrol agent with in planta antimicrobial activity against Fusarium oxysporum f.sp.…”

Bacillus amyloliquefaciens strain 32a as a source of lipopeptides for biocontrol of Agrobacterium tumefaciens strains

“…; Yangui et al . ). To limit its spread, the Tunisian Ministry of Agriculture authorizes trade of nursery productions only if they bear <1% visible galls (Rhouma et al .…”

Efficacy ofEucalyptus cinereaas a Source of Bioactive Compounds for Curative Biocontrol of Crown Gall Caused byAgrobacterium tumefaciensStrain B6

“…Furthermore, infected plants are more likely to suffer from secondary infections and environmental stresses [ 3 ]. Prophylactic measures are the most used prevention approach [ 4 ]. Despite the precautions taken, the crown gall control is still very difficult because of its easy spread to other hosts.…”