Crown Gall Disease in Moroccan Almond Trees: Tumorigenic Bacteria and Sustainable Management through Biological Control

Abstract

Crown gall is a globally recognized bacterial disease caused by Agrobacterium tumefaciens. This bacterium is characterized by its potential to infect a wide range of plants, specifically fruit trees. In Morocco, almond trees (Prunus amygdalus) are among the most heavily affected species by this disease. In our study, all tested bacteria were isolated in the laboratory from infected almond samples exhibiting tumors at the crown and root of the sampled trees collected from northwestern of Morocco. Biochemical, pathogenicity and molecular identification were performed to identify the causal agent of almond crown gall. Molecular identification was done using a duplex PCR (A/C9 and A/E9) targeting virD2gene located in the pTi plasmid, which is the oncogenic element of the bacterium. The results showed that 12 from 20 isolates were identified as tumorigenic A. tumefaciens with the presence of pTi. Moreover, these isolates were found to exhibit tumorigenic properties both in vitro and in vivo when tested on indicator plants, specifically tomato and carrot discs. The efficacy of agrocin synthesized by Agrobacterium radiobacter strain K1026, a biopesticide known as NoGall, was tested in vitro and in planta against tumorigenic strains of A. tumefaciens. Our results revealed a significant inhibitory effect in vitro, with inhibition percentages ranging from 29.5% to 38.9%. Additionally, we observed a complete reduction in tumor growth at the inoculation sites on indicator plants, with a 100% reduction percentage.

Keywords

• amandier
• galle du collet
• agrobacterium tumefaciens
• agrobacterium radiobacter
• k1026
• agrocin
• lutte biologique