Characterisation of rice (Oryza sativa) F3 populations selected for saltresistance. 2. Relationships between yield-related parameters andphysiological properties

Abstract

One somaclonal family (1-23) regenerated from a salt-resistant callus, its initial cultivar I Kong Pao (IKP, salt-sensitive), the breeding line IR31785 (extremely salt-sensitive), the moderately salt-resistant cultivar Aiwu and F3 populations derived from several crosses were exposed until maturity to a low sub-lethal (30�mmol�NaCl/L) dose of salt. The agronomic performance of this material was compared with its physiological behaviour, as recorded during the vegetative growth phase. Although grain yield of 1-23 was similar to the yield of its initial cultivar IKP in both control and salt-stress conditions, a strong increase in salt resistance in terms of grain yield per plant was observed in their F3 population derived from IR31785 × 1-23, which performed better than the corresponding parents and better even than the cultivar Aiwu in the presence of 30 mmol/L NaCl. Such improvement was due to a high number of spikelets per plant and a high spikelet fertility. An improved salt resistance in terms of grain yield was also observed in the F3 population derived from IR31785 × IKP. Among physiological parameters, only K : Na ratios quantified in stress conditions are useful as a predictive criteria for yield potential, and salt resistance to low NaCl does not involve any adaptation to the osmotic component of salt stress. No physiological parameters quantified in the absence of stress were correlated with yield in the presence of NaCl. Results are discussed in relation to the usefulness of somaclonal variation for plant breeding.