Colonization of arbuscular-mycorrhizal fungi on Ri T-DNA transformed roots in synthetic medium.

Hairy root culture of tomato (Lycopersicon esculantum L.) was induced with three strains of Agrobacterium rhizogenes namely A4, ATCC 15834 and LBA 9402. The best response in terms of growth of hairy root was observed with A. rhizogenes strain A4 and LBA 9402 followed by ATCC 15834. Hairy roots were maintained on Murashige and Skoog (MS) medium but it could also grow on minimal (M) medium. Spores of Gigaspora margarita were isolated by wet sieving and decanting method and further recovered by sucrose density gradient method. A new method for surface sterilization of spores has been described which is simpler than the methods described earlier. Surface sterilized spores of G. margarita were used for inoculation of transformed roots grown on M medium as it was found more favourable for germination and growth of spores. During co-cultivation, mycorrhizal spore germination and its penetration into root cortex were observed. Inter and intracellular mycelial spread and formation of arbuscules were also observed in the cortical region of transformed roots of this plant.