crown gall tumours
Crown gall tumors, also known as Agrobacterium tumefaciens-induced tumors, are plant diseases caused by the bacteria Agrobacterium tumefaciens. The tumors usually appear as abnormal growths or swellings on the stems, roots, or upper parts of multiple plant species, including fruit trees, ornamental plants, and crops.
The bacteria enter the plant through wounds or natural openings and transfer a segment of their DNA called a T-DNA into the plant cells. The T-DNA then integrates into the plant's genome, causing it to produce large amounts of plant hormones called auxins and cytokinins. The increased production of these hormones leads to uncontrolled cell division and the formation of tumors.
Crown gall tumors can vary in size, shape, and appearance, depending on the plant host and the location of the infection. They can range from small, bumpy growths to large, irregular masses. In some cases, the tumors can cause stunted growth, reduced yield, or even death of the plant if they extensively disrupt the plant's vascular system.
Control and management of crown gall tumors involve several approaches, including preventing wounds on plants, using pathogen-free planting material, and applying biological control agents. Chemical treatments, such as antibiotics and disinfecting agents, can be used in severe cases.
Overall, crown gall tumors can have significant economic and aesthetic impacts on agricultural and horticultural industries due to reduced crop quality and value. Efforts to prevent and control this disease are important in maintaining plant health and productivity.
Crown gall tumors are abnormal growths that develop on the stems, branches, and roots of plants. They occur due to infection by a bacterium called Agrobacterium tumefaciens. Here are the step-by-step explanations of crown gall tumors:
1. Infection: The Agrobacterium tumefaciens bacterium enters the plant's tissues through wounds, such as pruning cuts or insect feeding sites. Once inside, it can transfer a piece of its DNA called a Ti (tumor-inducing) plasmid into the plant cells.
2. Transfer of DNA: The Ti plasmid contains specific genes called oncogenes that can manipulate the plant's normal cellular processes, causing uncontrolled cell division and tumor formation. The bacterium transfers a portion of its Ti plasmid DNA into the plant cells, causing the plant's cells to divide uncontrollably.
3. Tumor formation: As the plant cells divide rapidly, a lump or tumor-like growth called a crown gall appears on the plant. The tumor can vary in size and can be smooth or rough in texture. It is typically localized around the site of infection.
4. Tumor characteristics: The crown gall tumor is often firm, rough, and can be atypical in appearance compared to the normal plant tissue. It may vary in color, usually ranging from whitish to light brown or reddish.
5. Plant response: The presence of the crown gall tumor can stimulate the plant's defense mechanisms, leading to the development of corky tissue around the tumor. This corky tissue acts as a barrier, isolating the infected area from the healthy plant tissue.
6. Impact on plants: Crown gall tumors can adversely affect the affected plants. The tumors can disrupt normal nutrient flow within the plant, leading to stunted growth, reduced vigor, and sometimes death if the infection is severe and widespread.
7. Management: Strategies for managing crown gall tumors include preventive measures such as avoiding plant injuries, using healthy planting material, and maintaining good overall plant health. Additionally, removing and destroying infected plant parts can help reduce the spread of the disease within a garden or orchard.
It's worth noting that crown gall tumors can affect a wide range of plant species, including fruit trees, roses, and other ornamental plants. Understanding the biology and management of crown gall tumors can help gardeners and farmers effectively control and minimize their impact on plants.