Symptoms
Hairy root disease is characterized by an overabundant growth of adventitious roots at the site of infection (usually on the stems of plants near and immediately below the soil surface). Symptoms of hairy root disease may also include wrinkled leaves. Hairy root disease symptoms have been divided into 2 categories, ‘simple or fibrous hairy-root’ and ‘woolly-knot form of hairy root.’ Simple hairy root disease is identified as stated above where as the woolly-knot form is characterized by the initial formation of a smooth tumor on the plant stem followed by an outgrowth of adventitious roots from the tumor surface. The high variability of the plasmids in R. rhizogenes strains is the reason that many strains are capable of inducing excessive root growth as well as tumor growth (1).