Evaluating the effectiveness of rhizobacteria producing 1-aminocyclopropane-1-carboxylic acid deaminase in inhibiting tumor formation by Agrobacterium tumefaciens

Abstract

AbstractCrown gall is one of the most dangerous bacterial diseases affecting the production of fruit tree nurseries in Egypt and many countries of the world. In the present study, ten isolates of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing rhizobacteria were isolated from the rhizosphere of apricot (Prunus armeniaca L.) and plum (Prunus domestica L.) trees to evaluate their ability to decrease tumor formation by Agrobacterium tumefaciens (synonym Rhizobium radiobacter). The ten isolates were identified as Pseudomonas strains based on 16S rRNA gene sequence analysis and deduced protein sequences obtained from a partial ACC deaminase structural gene (acdS) sequence. Co-inoculating castor bean (Ricinus communis L.) and kalanchoe (Kalanchoe sp.) plants with A. tumefaciens and four ACC deaminase-producing Pseudomonas isolates decreased tumor formation. However, six ACC deaminase-producing Pseudomonas isolates produced varying results in these two plant species. The results showed that isolates of Pseudomonas vancouverensis reduced tumor formation when co-inoculated with A. tumefaciens in castor bean and kalanchoe plants. However, the isolate P. putida inhibited tumor formation in castor bean plants but did not achieve the same effect in kalanchoe plants. Additionally, isolates of P. frederiksbergensis and P. kilonensis decreased tumor formation in kalanchoe plants while increasing tumor formation in castor bean plants. The results showed that ACC deaminase-producing P. vancouverensis is a promising biocontrol agent against A. tumefaciens.