Management of Asiatic Citrus Canker Under Field Conditions in Saudi Arabia Using Bacteriophages and Acibenzolar-S-Methyl

Abstract

Applications of formulated bacteriophages with skim milk and sucrose or nonformulated bacteriophages combined with acibenzolar-S-methyl (ASM) were compared with copper bactericides applications for suppressing Asiatic citrus canker (ACC) caused by Xanthomonas citri subsp. citri (Xcc) on leaves under greenhouse and field conditions in Saudi Arabia. Bacteriophages were applied one day prior to inoculation of Mexican lime (Citrus aurantifolia) plants with Xcc, then twice a week until the end of the trials. Copper hydroxide was applied once prior to inoculation and then every seven days afterward, whereas ASM was applied one week prior to inoculation and then every 21 days afterward. Under greenhouse conditions, the incidence of ACC on leaves was reduced significantly from 75.2 to 12.8% or 18.3% for plants treated with copper hydroxide or bacteriophages in combination with ASM, respectively. Applications of formulated phages in combination with ASM as soil drench under field conditions significantly decreased disease incidence by 14.8% (Trial 1) and 16.8% (Trial 2) compared with untreated control plants. Overall, the Xcc-inoculated plants treated with bacteriophages + ASM combination showed significant ACC reduction under greenhouse and field conditions. The bacteriophages + ASM combination tested in these trials can be an effective tool in the integrated management programs of Asiatic citrus canker disease.

Bacterial Citrus Diseases: Major Threats and Recent Progress

“…Hence, there is an urgent need to find alternative control strategies. Significant reductions in the percentage of infected leaves and disease intensity were obtained by application of phages isolated from infected leaves or their combination with acibenzolar-S-methyl (ASM) onto Mexican lime (C. aurantifolia) plants previously inoculated with Xcc under greenhouse and field conditions [109]. Similar results had previously been reported [110].…”

Preparing for the KIL: Receptor Analysis of Pseudomonas syringae pv. porri Phages and Their Impact on Bacterial Virulence

“…One of the limitations of phages is their applicability in field conditions, as the viruses are subjected to abiotic (and biotic) stresses (i.e., rain, wind, UV light, temperature) [2,33,34]. In some pathosystems, researchers try to overcome the limited stability of phages in these conditions by adding additives like skimmed milk and sugars which allow the phages to remain present on the aerial parts of the plants and increase their efficacy [33,35]. In the case of leek plants, the outbreak of the disease occurs through infected seeds or at plant nurseries [10,36].…”

Framing the Future with Bacteriophages in Agriculture

“…Efficacy of both options should be evaluated as part of a biocontrol development program. Aerial phage applications require formulations that will ensure the survival of the phage in the environment [ 60 , 61 , 76 , 86 ]. The alternative application methodology is to utilize a living bacterial cell delivery system that ensures survival and continued replication of the phages prior to the arrival of the pathogen [ 16 , 65 ].…”

“…Similar results were seen for CBS, where phage control was significantly different from the control in Valencia oranges but not in grapefruit under low disease pressures [ 60 ]. Ibrahim et al [ 61 ] obtained successful control of Asiatic citrus canker in greenhouse and field trials, by combing a compound which induced the plants systemic acquired resistance and phage mixtures formulated in skim milk and sugar.…”