Breeding for Yield Potential and Stress Adaptation in Cereals

Abstract The need to accelerate breeding for increased yield potential and better adaptation to drought and other abiotic stresses is an issue of increasing urgency. As the population continues to grow rapidly, the pressure on resources (mainly untouched land and water) is also increasing, and potential climate change poses further challenges. We discuss ways to improve the efficiency of crop breeding through a better physiological understanding by both conventional and molecular methods. Thus the review highlights the physiological basis of crop yield and its response to stresses, with special emphasis on drought. This is not just because physiology forms the basis of proper phenotyping, one of the pillars of breeding, but because a full understanding of physiology is also needed, for example, to design the traits targeted by molecular breeding approaches such as marker-assisted selection (MAS) or plant transformation or the way these traits are evaluated. Most of the information in this review deals with cereals, since they include the world's main crops, however, examples from other crops are also included. Topics covered by the review include the conceptual framework for identifying secondary traits associated with yield potential and stress adaptation, and how to measure these secondary traits in practice. The second part of the review deals with the real role of molecular breeding for complex traits from a physiological perspective. This part examines current developments in MAS and quantitative trait loci (QTL) detection as well as plant transformation. Emphasis is placed on the current limitations of these molecular approaches to improving stress adaptation and yield potential. The essay ends by presenting some ideas regarding future avenues for crop breeding given the current and possible future challenges, and on a multidisciplinary approach where physiological knowledge and proper phenotyping play a major role. Keywords: breedingcerealsdroughtyield potential ACKNOWLEDGMENTS We are very grateful to Prof. Martin AJ Parry, Head of Plant Science Centre for Crop Genetic Improvement, Rothamsted Research (Email: martin.parry@bbsrc.ac.uk) and Prof. Roberto Tuberora, head of the Biotechnology Applied to Plant Breeding Group, Department of Agroenvironmental Sciences and Technology, University of Bologna, (roberto.tuberosa@unibo.it) for their very valuable comments and corrections. This study was supported in part by the European research project OPTIWHEAT (INCO-STRIP 015460) and by the Spanish Ministry of Science and Technology projects, AGL-2006-13541-C02-1 (for J.L. Araus and M.D. Serret), AGL 2006-07814/AGR (for G.A. Slafer) and AGL-2006-09226-C02-01 (for C. Royo). Referee: Richard Richards, Program Leader, 'High Performance Crops for Australia', CSIRO Plant Industry, POB 1600 Canberra 2601 Notes a Additive effect for grain yield (q ha− 1) computed as half of the difference between the mean phenotypic values of the RILs homozygous for the Svevo and Kofa alleles [(Svevo – Kofa) / 2]. † QTLs influencing more than one trait in a range of environments.