Genomic Approaches to Understand Varietal Differences in Rice Species and Genotypes with Respect to Stress Response and Quality Traits

Abstract

Rice is one of the major food crops feeding more than 3.5 million people worldwide, especially in developing countries. The emerging population demands increased production of rice with improved quality and traits which is a challenge for sustainable rice cultivation. Although the rice production over the past decade is increasing annually, yet it is not sufficient to meet the need. Elevated demands for rice need increased production for which abundant arable land is unavailable, especially in Asian countries where more than 90% of rice is produced and consumed. Under a variable range of agroclimatic conditions, rice is produced across the world, so it is highly prone to a wide range of abiotic stress conditions including extreme temperature changes, heavy metal toxicity, salinity, and drought stress. Conjunction of various abiotic stresses is more common in field conditions, and abiotic stresses seldom occur singly. Different rice genotypes respond differentially to abiotic stress, and variance of intraspecific responses can be noted within indica and japonica varieties. Responses to abiotic stress tolerance is a complex trait, although many genes related to abiotic stress response have been identified, yet there remain gaps which are needed to be bridged for complete understanding of the differential varietal traits. Functional genomics has revealed more than 2000 genes which have been cloned and partially characterized; genome-wide expression profiling of rice varieties, mutants, and transgenics have also aided the development as well. Molecular regulatory networks involved in several agronomic traits have been investigated. Newer fields of proteomics, metabolomics, phenomics, and epigenomics have also aided the functional genomics research in the recent times. We briefly review here the recent developments in rice functional genomics research that are of paramount significance in understanding the responses and quality traits of rice varieties to abiotic stress.