Characterization of rice (Oryza sativa L.) F3 populations selected for salt resistance. I. Physiological behaviour during vegetative growth

Plants belonging to a somaclonal family (R₃-1-23, obtained from a salt-resistant callus of the salt-sensitive cultivar I Kong Pao (IKP, salt-sensitive)) were crossed with this intital cultivar IKP or with plants of the elite breeding line IR31785 (IR31, extremely salt-sensitive). Two other crosses were also performed: IR31 × IKP and IKP × Aiwu, where Aiwu is a moderatly salt-resistant cultivar. The physiological behaviour of F₃ populations was analysed after 21 and 42 days of exposure to 0 or 30 mM NaCl and compared to the behaviour of plants selected within parental populations. A clear improvement in terms of survival percentages was demonstrated for plants issued from IR31 × 1-23 and IR31 × IKP. These F₃ populations exhibited lower Na accumulation in shoots, higher Ca accumulation in roots, higher ratios of shoot P/root P than the parents after 42 days of salt exposure. Salt stress induced a decrease of shoot K, an increase of shoot Cl and proline and a decrease of osmotic potential in all populations. Correlation analysis indicated that no physiological parameter recorded in the absence of salt stress may be used as a reliable selection marker to predict the plant behaviour in salt stress conditions. K/Na ratio recorded in the stressed plants was significantly correlated with surviving percentages recorded after 90 days of salt stress, suggesting that this physiological parameter in stress conditions appears to be the most reliable selection criterion for salt resistance in rice. This revised version was published online in August 2006 with corrections to the Cover Date.