Screening lowland transgenic rice for drought tolerance: from the lab to the rice field

In light of the challenges ahead to guarantee food security of the world's poorest, several institutions are investing in transgenic technology for complex genetic traits such as drought tolerance. Rice is an ideal candidate because of its potential or high impact in developing countries. First, it is most important staple food crop for the developing world, where up to 40% of the rainfed production area is subjected to unpredictable drought. Additionally, rice is well suited for high-throughput genetic transformation, and significant genomic and functional gene studies are available to target candidate genes. Although the number of publications claiming increased drought tolerance in transgenic genotypes had increased exponentially over the last decade, progress has not reached farmers' fields. One reason is that, unlike conventional breeding, transgenic studies seldom report grain yield in various field environments. The collaborative effort presented here is setting a precedent by moving transgenic evaluation from the laboratories to the fields using breeding approaches with large-scale screenings for yield stability under drought . The authors intent to address the opportunities and challenges and share learning from the screening of nearly 500 transgenic events pertaining to 19 gene constructs in confined screenhouses and field trials. Transgenic plant performance is rarely consistent under different drought scenarios, highlighting the diversity of mechanisms necessary to cope with water shortage and the challenges in finding robust tolerant plants. The authors have identified 25 promising events showing improved yield and/or water uptake under drought compared with wild types. Those events are being tested to pinpoint the drought tolerance mechanisms involved. The next step will be to test promising lines in various drought-prone Asian regions in various varietal backgrounds adapted to different types of drought. IRRI's experience with Asian research partners who have established biosafety frameworks and approved transgenic nutritionally improved rice will be an important asset.