Physiological evaluation of wheat (Triticum aestivum L) genotypes for drought resistance

Abstract

Thirty seven percent of the area in the developing countries consists of semi-arid environments in which available moisture constitute a primary constraint on wheat production. Climatic variability in these marginal environments causes large annual fluctuations in yield. Several strategies have been devised to overcome the problem of drought stress. In this connection, a few of the numerous drought screening tests have been identified for their use in breeding programme [1]. Assessment of water loss from excised leaves (ELWL) has shown promise for characterising drought resistance in wheat genotypes [2]. Relative water content (RWC) has also been reported as an important indicator of water stress in leaves, it closely reflect the balance between water supply to the leaf and transpiration rate [3]. This influences the ability of the plant to recover from stress and consequently affects yield and yield stability. Canopy temperature measured under drought stress has also been developed into a rapid field screening method for the maintenance of plant water status under drought stress. Relatively lower canopy temperatures under stress indicate a relatively better plant water status and canopy temperatures were generally found to be negatively correlated with yield under stress. Cell-membrane stability (CMS) is considered to be one of the major selection indices of drought tolerance in cereals [4] it is estimated in leaves subjected to advanced stress, typical to RWC of around 60-70%. The first case of such a study is in rice where OTLs for CMS under drought stress were identified [5]. Genetic variation for yield as well as drought resistance index is limited. However, it can be further exploited by identifications of single or multiple physiological traits for drought resistance. The aim of this study was to establish the extent of genetic variation and to assess the drought tolerance among the wheat genotypes on the basis of drought resistance index and water relation parameters.