ABSTRACT
Abstract. Soil salinity is a foremost abiotic stress for agriculture, sturdily influencing plant productivity worldwide. The reduction of productivity in saline soils can be overcome by soil reclamation or by improving salt tolerance in target plants. Plant salt tolerance is a complex trait affected by numerous genetic and nongenetic factors, and its improvement via conventional breeding is less noteworthy. Recent advancements in biotechnology have led to the development of more efficient selection paraphernalia to substitute phenotypebased selection. Gene(s) or quantitative trait loci (QTLs) that affect important traits and association with molecular markers have been identified, which could be used as indirect selection criteria to improve breeding effectiveness by means of marker-assisted selection (MAS). While the use of MAS for manipulating simple traits has been rationalized in many plant breeding programs, MAS for improving complex traits seems to be at the beginning stage. In the last decade, a rapid progress has been made toward the development of molecular marker technologies and their application in constructing linkage maps, molecular dissection of the complex agronomical traits, and marker-assisted breeding (MAB). The basis of MAB approach is to transfer a specific
allele at the target locus from a donor line or variety to a recipient line/variety while selecting against donor introgressions across the rest of the genomes. Molecular marker and its use permit the genetic dissection of the progeny at each generation and increase the speed of the selection process, thus increasing genetic gain per unit time. The main advantages of MAB are (1) efficient foreground selection for the target locus, (2) efficient background selection for the recurrent parent genome, (3) linkage drag minimization surrounding the locus being introgressed, and (4) rapid breeding of new genotypes with favorable traits. The effectiveness of MAB depends on the availability of closely linked markers and/or flanking markers for the target locus, the size of the population, the number of backcrosses, and the position and number of markers for background selection. Numerous QTLs have been reported for ST in different crop species; however, few commercial cultivars or breeding lines with improved ST have been developed by the use of MAS. Strategies and current status of MAS, MAB, QTL mapping, genetic engineering, and application of RNAi are discussed in this chapter, which are important to learn for the development of salt-tolerant plants.
