GENE ACTION ARRAY RELATED TO MORPHO-PHYSIOLOGICAL TRAITS USING POPULATION GENETICS IN Triticum aestivum L.

Wheat, a rich source of energy, is most important cereal crop in world which provides more than 50% calories of daily intake to the world population (FAO, 2015). Wheat is sensitive to abiotic stresses. Under water limited conditions plants cannot perform normal physiological activities thus resulting in loss of yield (Said, 2014). Availability of useable irrigation water is decreasing in inverse proportion to an everincreasing human population (Vorosmarty et al., 2000). To keep up with increasing population, wheat should be tailored against water scarce environments. Plant response to drought is a complex phenomenon (Reddy et al., 2004). Drought affects plant osmotic potential and ionic equilibrium resulting in complete or partial blockage of vital physiological processes such as photosynthesis. Photosynthetic rate is primary physiological process which indicates the amount of CO2 consumed and glucose produced by the plant. In the absence of glucose plant cannot produce energy resulting in death of plant cells (Reddy et al., 2004). Water stress also affects plant at different levels of structural organization. Limited water supply causes certain morphological changes in plants like wilting and shrinking of leaves, elongation of roots but reduction in root thickness, reduction in stomata counting, thickening of cell wall of leaves, deposition of epicuticular wax causing reflection of sunlight, development of conductive system, large vessels increased, early maturity, senescence and tube leaves formation in cereals. To maintain plant’s internal water supply, roots elongate in the soil causing increase in root to shoot ratio due to increase in the production of abscisic acid (ABA) in the roots (Chandrasekar et al., 2000). So, keeping in view the scarcity of water, it is need of time to develop plants which can perform better under water scarce conditions (Novoselovic et al., 2004). To develop drought tolerant cultivar, knowledge about genes which are controlling the principle parameters and are vital for production under drought conditions is important (Tonk et al., 2011). Genetic analysis related to certain traits in wheat has already been reported for stomatal conductance (Rebetzke et al., 2003b; Farshadfar et al., 2013a), photosynthetic rate (Simon, 1994; Rebetzke et al., 2006b), excised leaf water loss (Farshadfar et al., 2001b), Relative water content (Farshadfar et al., 2001b; Golparvar et al., 2006b; Farshadfar et al., 2013b) and grain yield per plant (Khan et al., 2000; Akhtar and Chowdhry, 2006; Ullah et al., 2010; Rashid et al., 2012). Selection efficiency in segregating populations can be estimated using heritability and genetic advance. Yield improvement can be done by improving selection efficiency. Simon (1994) showed high heritability estimates for number of grains per spike and grain yield per plant. Rebetzke et al. (2006b) revealed high genetic advance for relative water contents. Visscher et al. (2008) showed low heritability and Pak. J. Agri. Sci., Vol. 55(3), 513-519; 2018 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/18.5149 http://www.pakjas. com.pk