Quantitative trait loci and crop performance under abiotic stress: Where do we stand?
Résumé
The improvement of crop yield has been possible through the indirect manipulation of quantitative trait loci (QTLs) that control heritable variability of the traits and physiological mechanisms that determine biomass production and its partitioning. This article surveys how QTL-based approaches contribute to a better understanding of the genetic basis of crop performance under environmentally constrained conditions and critically analyzes how this knowledge can assist breeders accelerate the release of cultivars better able to cope with abiotic constraints. Crop performance is the end result of the action of thousands of genes and their interactions with environmental conditions and cultural practices. During the past century, conventional breeding has been very successful in constantly raising the yield potential of crops (Campos et al., 2004Go; Borlaug and Dowswell, 2005Go; Duvick, 2005Go). This was mainly achieved with little or no knowledge of the factors governing the genetic variability exploited by breeders for crop improvement (Blum, 1988Go; Borlaug, 2007Go). However, this approach may now be insufficient, because the pressure to provide improvements at a rapid pace will mount if global climate change increases the frequency and severity of abiotic constraints. Heat stress, drought, water-logging, and salinity will probably become more prevalent in certain areas, while there will be an increased demand for agricultural products and reduced availability of agricultural land and natural resources such as water and fertilizers. Consequently, the genetic dissection of the quantitative traits controlling the adaptive response of crops to abiotic stress is a prerequisite to allow cost-effective applications of genomics-based approaches to breeding programs aimed at improving the sustainability and stability of yield under adverse conditions.