Stress responses and adaptation in crops involve complex mechanisms since the plants must respond to variable stress occurrence parameters and interacting environmental factors. However, experiments describing the enhancement of stress resistance by a transgenic approach are usually restricted to the modulation of the plant response to one stress factor. In this note, we review examples from the recent literature and focus, in more detail, on the methodology and the results of seven published studies that describe the enhancement of drought resistance in rice using various strategies (transcription factors, cell metabolism, water fluxes, and reactive oxygen species scavenging). Although the transformation methodology is somehow similar, the protocols for plant evaluation and the parameters used to assess plant resistance are diverse and difficult to compare. The low number of independent transgenic lines and the poor assessment of a gene effect versus an overall effect due to gene insertion and somaclonal variation could be major drawbacks. The relevance of some screening methods for drought is questionable from a breeding perspective and only a few studies provide actual data about enhanced drought resistance under field conditions. In addition, it is noteworthy to observe that most of the experiments are based on the overexpression of a single gene. If the use of transgenic crops could potentially enhance drought responses of plants by promoting changes in the genome, there is clearly an important need to define or redefine the major steps and criteria to obtain better crop performance in the field. We summarize in this paper some of the major steps and key criteria to identify better rice cultivars with enhanced drought resistance using GM technology.
In: Drought frontiers in rice – Crop improvement for increased rainfed production (Serraj R, Bennett J and Hardy B, eds). World Scientific Publishing Co., Singapore, pp 333–350 (DOI: 10.1142/9789814280013_0019). ISBN: 978-981-4280-00-6.