Physiological characterisation of salt-resistant rice (Oryza sativa) somaclones

The progenies of 90 R-0 plants regenerated from mature embryo-derived rice (Oryza sativa L.) calli obtained from two cultivars (I Kong Pao, salt-sensitive and Aiwu, moderately resistant) exposed to NaCl stress at various steps of in vitro culture, were screened for their salinity resistance in nutritive solution. Sixteen R-1 families presented a higher survival rate in stress conditions than their corresponding initial cultivar and several of them exhibited an improvement in the mean number of spikelets per panicle and total grain weight produced per stressed plant. In four cases, the better behaviour of the somaclonal family could be related to physiological modifications such as a higher K+:Na+ discrimination, preferential Na+ accumulation in the oldest leaves, lower decrease in cell membrane stability or higher tissue tolerance to internal Na+ accumulation. In some cases, these physiological properties were transmitted to R-2 progenies. Heritabilities of yield-related parameters were quantified in control and stress conditions. The relationships between these parameters and the physiological behaviour of stressed material are discussed in relation to the effectiveness of in vitro culture techniques for the selection of salt-resistant plants in rice compared with a simple mass selection.