Hairy root
Agrobacterium rhizogenes
what is Hairy root (Agrobacterium rhizogenes)?
Agrobacterium rhizogenes is a bacterium responsible for causing hairy root disease in plants. It has a wide distribution and can infect several broadleaved plants like blueberries, cranberries, fruit and nut trees, and roses. Infected plants exhibit the formation of dense clusters of small, abnormal roots, which give them an unhealthy appearance. The impaired root system hampers nutrient and water uptake, leading to symptoms such as foliage yellowing, stunted growth, and premature death.
How does Hairy root (Agrobacterium rhizogenes) occur?
Agrobacterium rhizogenes reproduces and spreads through the transfer of its genetic material into plant cells. When the bacterium encounters a wounded plant tissue, it uses a specialized mechanism to transfer a segment of its DNA, known as the Ri (root-inducing) plasmid, into the plant cells. This transferred DNA integrates into the plant's genome, causing abnormal growth and the formation of hairy roots. The bacterium can persist in the soil and spread to other plants through water or via wounds, facilitating the infection and reproduction cycle.
Symptoms
1 - Effects on Plants
• Agrobacterium rhizogenes cause abnormal root growth, forming dense clusters of small, abnormal roots (hairy roots). • This impairs plant growth and can lead to stunted growth, nutrient deficiencies, and premature death.
2 - Effects on Soil
Agrobacterium rhizogenes can persist in soil, increasing the risk of future infections. It may disrupt the natural balance of soil microorganisms, impacting nutrient cycling and soil health.
3 - Effects on Environment
• The bacterium can spread through water, contaminating water sources and potentially infecting other susceptible plants. • It poses a risk to plant diversity, affecting horticultural and ornamental plants and potentially disrupting ecosystems.
Solutions
1 - Prevention
• Source high-quality nursery stock from reputable suppliers to reduce the risk of introducing infected plants. • Avoid injuring plants during transplanting, as wounds provide entry points for the bacterium. • Practice good sanitation, including cleaning and disinfecting tools and equipment, to minimize the spread of the bacterium.
2 - Treatment
• Remove and destroy infected plants to prevent further spread. • Employ soil solarization during the hot dry season before planting to reduce the abundance of the bacterium in the topsoil. • Utilize biological control agents or beneficial microorganisms that can compete with Agrobacterium rhizogenes and suppress its growth. • In severe cases, chemical treatments may be used following the recommendations provided by local agricultural extension services or professionals.
