Gene Regulation and Biotechnology of Drought Tolerance in Rice

Drought is one of the main factors affecting rice productivity. Aromatic Rice varieties differ in their ability to withstand drought while keeping characteristic fragrance. Considering that 70% of the water used by humankind is directed to irrigate crops, tolerance to water scarcity is also a key issue for agricultural sustainability. The understanding on the mechanisms underlying drought tolerance observed in some varieties will be valuable for the agronomical improvement of rice. We have addressed the problem of drought tolerance in aromatic rice using a multidisciplinary approach, integrating plant physiology, transcriptomics, microtranscriptomics, proteomics and biotechnology. Rice plants from three drought tolerant and three drought sensitive varieties were cultivated in the field. Plants were watered or not and leaf and first internode samples were taken three, seven and eleven months after planting (MAP). Several parameters were also evaluated, such as gas exchange, proline content, leaf area, internode diameter and productivity. Plant responses to drought included reduction of the leaf area, lower stomata conductance and lower leaf osmotic potential, as well as dynamic photoinhibition and induction of leaf proline content. No differences could be seen between the two groups (tolerant and sensitive) at three MAP. Photosynthesis was higher in drought tolerant plants at seven MAP and this difference was also noted at eleven MAP, although not at the same level as observed at seven MAP. Proline content had no correlation with drought tolerance in any of the three time points evaluated. As expected, plant productivity in the drought tolerant plants under drought conditions was higher than drought sensitive plants. R.S.Sengar et al 548