Evaluation on Drought Tolerance of Rice Lines with Indica Genetic Background Carrying Chromosome Segment Substitution from Wild Rice (Oryza rufipogon) or Japonica

Abstract

     Twenty chromosome segment substitution lines (CSSLs) developed from IR24 background (5 lines of Ruf Ils (IR24 × O. rufipogon), 15 lines of IAS (IR24 × Assominori - a Japonica cultivated rice) and IR24 were evaluated for drought tolerance at tillering stage. The 3-leaf seedlings were grown in Kimura B + 20% PEG6000 solution (drought treatment) or in Kimura B solution (non-drought treatment). The results showed that, the drought resistance index (DRI) correlated with the dry matter under drought and non-drought conditions with r = 0,614 and r = 0,604, respectively. The number of leaves, leaf area, root surface area, number of roots and root hairs in both CSSLs and IR24 were reduced in drought condition. But, there was no reduction in root numbers and root hairs numbers in CSSLs, which had higher DRI. The results also showed that, drought tolerance mechanism of IAS lines might involve the increase of root growth, water uptake and root-to-shoot water transport. However, the mechanism in Ruf ILs lines might involve the reduction of leaf number, leaf area and in company with increase of root growth and water uptake. These finding suggested that wild rice O. rufipogon and Asominori would be ideal materials for rice breeding for drought tolerance.