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' (IKP). The family R-2-1-23, in the presence of NaCl exhibited higher yield performances than the initial cultivar. This improvement in salinity resistance, 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 used as parents for production of hybrids. Four crosses, IKP x R-3-1-23, IR31785 x R-3-1-23, IR31785 x IKP and IKP x 'Aiwu', were performed. Most of the F-1 hybrids cultivated in the absence of salt exhibited increased performances compared with the mid-parent. suggesting an heterosis effect for yield-related parameters. F-2 populations were screened for salinity resistance and a clear improvement for yield in stress conditions was recorded for populations 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 depending on the population, the presence or absence of stress, and the quantified 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