A RAPID SCREENING TECHNIQUE FOR SALT TOLERANCE IN RICE (ORYZA-SATIVA L)

An effecient, reproducible and simple mass screening technique for the selection of salt tolerant rice lines has been developed. Fourteen-day old seedlings raised in silica gravel culture were transplanted to foam-plugged holes in polystyrene (thermopal) sheets floated over 100 dm3 of nutrient solution in painted galvanised-iron growth tanks lined with plastic (120 x 90 x 30 cm). Three days after transplanting, NaCl was added to salinize the medium in increments, at the rate of 25 mol m-3 per 24 hours, up to the desired salinity levels which ranged from 50-200 mol m-3 NaCl. Six plants of each line were transplanted and allowed to grow for 15 days after the maximum desired stress level was achieved in each case. Absolute shoot fresh and dry weights, as well as percent mortality, were used as criteria for assessing relative salt tolerance. Related studies were also conducted to standardize the technique. The validity of this technique was tested by conducting experiments in salinised soil (pot culture) and in salt-affected field where 9 rice lines were grown up to maturity and absolute paddy yield was considered as the criterion for salt tolerance. Salt tolerance behaviour of cultivars based on different selection criteria was compared. Good reproducibility of results among the three solution culture experiments and their close association with the results of pot culture and of salt-affected field study, authenticated the validity of this technique for practical purposes.