Osmotin: A PR gene impart tolerance to excess salt in Indica Rice

Abstract

Agrobacterium-mediated genetic transformation (strain: GV2260 harbouring osmotin gene in a binary vector pGV2260 under the transcription control of CaMV 35S promoter and Nos terminator) was restored to develop productive salt tolerant transgenic rice varieties in a well adaptive high yielding indica rice background of var. Ananda. Out of 705 calli transformed, 426 survived (60.44%) on kanamycin (50 mg/l) supplemented MS medium, which could regenerate 78 plantlets of which 56 survived from 29 independent transformation events. Molecular analyses showed 23 PCR positive, 9 Southern positive and 6 plants positive to both PCR and Southern hybridization. Southern hybridization with radio-labeled osmotin probe showed transgene integration in 2-6 loci in 6 representative transgenic plants. Seed germination test involving seeds at T1 generation on MS medium containing 50mg/l kanamycin showed 3:1 ratio for majority of the lines albeit with a few exception, might be due to small sample size or epistatic interactions. Tolerance test to excess salt was conducted invivoon artificially stimulated NaCl stress under hydroponics involving Hoagland solution showed progenies of T46-1 were most tolerant to excess NaCl followed by the progenies of T2-6, which were planted on soil in cement pots in the Transgenic Rearing Facility (Category II, DBT approved) till maturity and harvested seeds were kept plant wise for subsequent generation advancement of most productive lines with desirable salt tolerance for cultivation enmasseunder saline soil for enhanced productivity under constrained soil at sustainable-scale in Andaman Islands and elsewhere.