Crosses between cultivars and tissue culture-selected plants for salt resistance improvement in rice, Oryza sativa

Several R-2 somaclonal families were derived from plants regenerated from a salt-resistant callus of the salt-sensitive rice cultivar 'I Kong Pao' (IK P). The family R-2-1-23, in the presence of NaCl exhibited higher yield per formances than the initial cultivar. This improvement in salinity resistanc e, however, was not transmitted to following generations, despite a higher number of spikelets per plant, family R-3-1-23 did not perform better than the initial cultivar because of a very low seed set. This somaclonal family , its initial being the cultivar IKP, the breeding line lR31785 (extremely salt-sensitive) and the cultivar 'Aiwu' (moderately salt-resistant), were u sed as parents for production of hybrids. Four crosses, IKP x R-3-1-23, IR3 1785 x R-3-1-23, IR31785 x IKP and IKP x 'Aiwu', were performed. Most of th e F-1 hybrids cultivated in the absence of salt exhibited increased perform ances compared with the mid-parent. suggesting an heterosis effect for yiel d-related parameters. F-2 populations were screened for salinity resistance and a clear improvement for yield in stress conditions was recorded for po pulations derived from IKP x R-3-1-23, IR31785 x R-3-1-23 and IR31785 x IKP , although the mean level of increase over the mid-parent (RIMP) varied dep ending on the population, the presence or absence of stress, and the quanti fied parameters. The results are discussed in relation to the usefulness of in vitro selection for obtaining interesting somaclonal variants useful to be integrated in classical breeding programmes for salinity resistance in rice.