Study of Agrobacterium-mediated co-transformation of tea for blister blight disease resistance

Blister blight is the most prevalent leaf disease of tea, an economical perennial crop. The disease is caused by a biotrophic fungus, Exobasidium vexans. The objective was set to study whether the combine over-expression of Solanum tuberosum class I chitinase gene and Vigna radiata defensin genes in transgenic tea would give more disease resistance compared to transgene over-expressed singly. Taking two constructs containing S. tuberosum class I chitinase (AF153195) and mung bean defensin (AY437639) gene respectively, three Agrobacterium-mediated transformation events were conducted with two individual constructs and combination of both the constructs. This is a first report about the preparation of transgenic tea by co-transformation for blister resistance. Transformation was successful in all three events. Comparative analysis showed a very interesting result. Minimum overall transformation efficiency was noticed in transformation of tea with pCAMBIA 1301-Chi (2.20%) followed by pBI121-Def (2.39%) and co-transformation with pCAMBIA 1301-Chi and pBI121-Def (3.41%). The fungal bioassay with E. vexans for the transformation event with pCAMBIA 1301-Chi gave the best disease resistance having minimum diameter (7.05 mm) of hypersensitivity zone followed by 15.05 mm in pBI121-Def and 18.14 mm in combination of pCAMBIA 1301-Chi and pBI121-Def.