Molecular Markers and Their Role in Producing Salt-Tolerant Crop Plants

Abstract

Besides drought and temperature, soil salinity is a severe abiotic environmental constraint to world agriculture, widely affecting yield and quality of crops. Increasing world population and simultaneous depletion of agricultural land created an alarming situation to meet the global food requirement. To meet this demand, it is imperative to utilize salt-affected land for agricultural produce. Researchers are actively engaged in developing salt-tolerant crop varieties using both conventional and molecular breeding technologies. Identification of salt-tolerant crop varieties using physiological and biochemical indices has become a routine technique in many laboratories. However, screening for salinity tolerance based on these indices relative to unstressed controls is labor-intensive and time-consuming. Moreover, results produced using these screening techniques are subjected to fluctuation in environmental conditions. In recent years, DNA-based molecular marker technique has been developed for screening salinity tolerance in crops. Molecular markers such as RFLP (restriction fragment length polymorphism), RAPD (random amplified polymorphic DNA), AFLP (amplified fragment length polymorphism), SSRs (simple sequence repeats), SRAP (sequence-related amplified polymorphism), ILPs (intron length polymorphism), and EST-SSRs (expressed sequence tags and simple sequence repeats) have been proven useful for rapid and sensitive screening of germplasm for salinity tolerance. However, raid advances in high-throughput sequencing technology make single-nucleotide polymorphism (SNP) become the marker of choice for salinity tolerance studies. Identification of genomic regions associated with salinity stress tolerance is of great significance which offers new avenues in marker-assisted selection breeding program. Molecular marker-assisted breeding may help in advancing fundamental understanding of salinity tolerance in crops. This book chapter provides a comprehensive review on the role of molecular markers as selection criteria for salinity stress tolerance in plants.