Establishment of hairy root lines of several economic plant species by inoculation with agrobacterium rhizogenes

Seedlings of 5 crop species ; Lactuca sativa L., Capsicum annuum L., Cucumis sativus L., Lycopersicon esculentum Mill. and Sesamum indicum L. were inoculated with 6 wild strains of Agrobacterium rhizogenes, A4, A13, C8, M123, 1724 and 15834. Hairy roots were induced from almost all the combinations, though the plant species showed marked differences in the per cent hairy root formation. The root cultures derived from the initial hairy root tips displayed the typical hairy root phenotypes such as vigorous growth, diminished geotropism and abundant lateral roots. Hairy roots of cucumber, tomato and lettuce kept growing vigorously in subcultures, while the growth of those of hot pepper and sesame suspended in a few rounds of subcultures. Addition of GA₃ to the culture medium effectively accelerated the growth of hot pepper hairy roots. The formation of green and compact calli from the hairy roots cultured on the media containing NAA and zeatin indicated that plant regeneration would be readily induced by modification of culture medium or environmental parameters.