Development of transgenic strawberry (Fragaria x ananassa Duch.) plants tolerant to salt stress

Transgenic technology provides currently the best hope for improvement in plants where traditional breeding is not feasible. Strawberry is one such plant where polyploidy complicates breeding efforts. Introduction of genes directly into strawberry has been successfully achieved. The study presented here is the first report where transgenic plants of strawberry tolerant to salt stress were produced. Leaf discs of in vitro grown plantlets of strawberry (cv. Chandler) were used as explants and Agrobacterium tumefaciens strain GV2260 harbouring osmotin gene under the control of CaMV 35S promoter in a binary vector system (pBinAR) was used in co-cultivation experiments. Transgene integration and copy number were assessed by PCR and Southern hybridization confirming single copy as well as multiple copies of transgene integration in 10 different lines of transgenic strawberry. Expression of osmotin gene was confirmed in transgenic lines TL3, TL5, TL9 using northern hybridization, while biochemical analyses of these transgenic plants revealed enhanced levels of proline, total soluble protein and chlorophyll content as compared to the wild plants. Leaf disc senescence assay showed that these transgenic lines were tolerant to salt stress. The growth pattern of transgenic plants overexpressing osmotin did not show any abnormality, except their growth rate being slower than other plants.