We are going to know the main characteristics of Agrobacterium tumefaciens. We will explain the symptoms of this disease, the affected hosts and a description of the bacteria. You should know that there is a way to control this bacterium through biological control. Let’s get to know it!

DESCRIPTION OF  AGROBACTERIUM TUMEFACIENS

Within the genus Agrobacterium we find two species: A. radiobacter , is a non-pathogenic bacterium that usually inhabits the soil, A. tumefaciens,  which is the one that produces the disease,  A. rizhogenes, which  causes root diseases,  A. rubi,  that causes tumors,

Agrobacterium tumefaciens  is a Gram-negative, rod-shaped bacterium with motility and peritrichous flagella (projecting in all directions). It is a non-sporulated bacteria and is chemo-organoheterotrophic, that is, it uses a wide range of carbon sources. The strains that cause neck or gall tumors in dicotyledons have a conjugative plasmid called   Ti , directly related to tumor induction.

 GUESTS OF AGROBACTERIUM TUMEFACIENS

In the case of Agrobacterium tumefaciens  the hosts are very broad. 643 species of 331 genera have been designated as hosts of the bacteria. They cover the following crops identified in Spain:

Apricot, almond, hazel, persimmon, cherry, plum, poplar, chrysanthemum, raspberry, apple, peach, quince, wicker, walnut, olive, pear, pepper, rose, willow and vine.

The main host of   Agrobacterium vitis Ophel and Kerr  is the vine or grapevine for the case of but it attacks any herbaceous and woody.

SYMPTOMS OF INFECTION

Tumors in the neck and gills are caused by an overproduction of auxins and cytokinins that cause abnormal cell growth, hypertrophy, and hyperplasia. These tumors can appear in the root, neck and aerial part, due to the fact that Agrobacterium travels systemically. The tumors that form in the neck of the plant tend to be the largest, appearing in clusters, forming chains of small tumors.

GEOGRAPHICAL DISTRIBUTION OF AGROBACTERIUM

This bacterium is currently widespread throughout all countries and continents. In Spain, it has been identified with special incidence in fruit and rose nurseries

The Agrobacterium vitis Ophel and Kerr bacteria  are distributed in the following geographical areas: Europe, America and Oceania. In the specific case of Spain, it can be found in any wine-growing area or even in nurseries.

BACTERIA TRANSMISSION

Transmission of the bacteria is simple. It can happen by the use of contaminated tools, transmission in the soil or by substrate or by water.

TUMORS OR GILLS

The disease initially manifests itself in the form of small swellings or excessive growths in any part of the plant, with a higher incidence near the soil surface (union between roots and graft). Aerial tumors are quite common in crops such as vine or grapevine. During the vegetative period, swellings appear on the plant, globular, whitish and soft in color, which over time lignify and continue to grow (up to 30 cm).

BIOLOGICAL CONTROL AGAINST AGROBACTERIUM TUMEFACIENS

It is a method highly developed by farmers from different countries. It consists of using an avirulent strain (strain 84) that produces a nucleotide bacteriocin that inhibits the vast majority of pathogenic agrobacteria. The material susceptible to infection by the virulent bacteria is immersed in a broth containing a cell suspension of the non-virulent bacteria.