Induction of hairy roots through the mediation of four strains of <i>Agrobacterium rhizogenes</i> on five host plants

122-128 Induction of hairy roots by four strains of Agrobacterium rhizogenes- ATCC 15834, A4, WC and WR were studied in five plants, Ipomoea batatas, Solenostemon rotundifolius, Vigna vexillata, Pachyrrhizus erosus and Canavalia species. Among the five plants selected for transformation and induction of hairy roots, P. erosus was found resistant to all the four bacterial strains. Similarly, one strain, WR also failed to induce hairy roots in all the plants. However, all the strains exhibited good growth dominated by 15834 grown in YEB medium. Hairy roots were induced from the cotyledons, hypocotyls, stem cuttings and in vitro plants of I. batatas through the transformation of 15834 and A4 strains. S. rotundifolius and V. vexillata were susceptible to the strains of A4, 15834 and WC. Canavalia sp. was resistant to WR and WC strains, but was susceptible to A4 and 15834. It was for the first time that hairy roots were initiated from S. rotundifolius, V. vexillata and Canavalia sp. The variation observed in the time of induction of hairy roots (incubation period) by a single strain (15834) in different plant species, suggests that the plant has also a definite role in determining the incubation period. Among the four strains of A. rhizogenes, 15834 was found to be the most efficient in transformation and initiation of hairy roots, with the shortest minimum incubation period and dominant growth in YEB medium. A. rhizogenes is a well known plant pathogen, which produces “hairy root disease” in susceptible plants. On modified MS medium, cotyledon explants were superior to hypocotyls. The hairy roots transformed by A. rhizogenes strain 15834 on I. batatas, V. vexillata and Canavalia sp. were also morphologically different.