Molecular tools for enhancing salinity tolerance in plants

Abstract

Salinity is nowadays considered one of the main factors that limit crop productivity and a threat to world's food production. Hence, to breed salt tolerant varieties of crops and horticultural species is necessary to increase or at least maintain food production in order to feed the growing world's population. Plant tolerance to salinity is a complex phenomenon at both cellular and plant level. Since salt causes several types of stresses, plants face salinity using different strategies, whose relative importance depends on the species and the growing conditions. Here we present an overview of the salt tolerance mechanisms to counteract osmotic, ionic and oxidative stress, as well as an update of the knowledge on the processes involved in salt tolerance gained in part through the new genomic approaches. To breed new cultivars able to grow and maintain crop productivity on saline conditions requires variability for some of the traits related to salinity tolerance, the discovery of quantitative trait loci (QTL) regulating those traits, a deep understanding of QTL interaction with other QTL and with the environment, and the transfer of QTL from donors to elite lines using phenotypic and marker assisted selection. We have summarised part of the information related to these four issues and some guidance is given to maximize the efficiency of the selection processes. Genetic transformation has become a powerful tool in plant breeding programs since it allows the introduction of gene(s) controlling traits without affecting the rest of the characteristics of an elite genotype. In this chapter we have reviewed the available information on several topics such as: salt tolerance improvement aided by genetic transformation, functional analysis of genes related salt-tolerance, the complexity of the trait and its evaluation method, the number of genes to be introduced, and the sources of genetic variability. Finally, the use of genomic tools like transcriptomic analysis, post-transcriptional gene silencing, insertional mutagenesis and gene traps, to perform the genetic dissection of this complex trait is discussed. © 2009 Springer Science+Business Media B.V.