Original paper 64 ~ M 14 Open Access Maydica electronic publication - 2019 Maydica Introduction Climate anomalies such as biotic and abiotic stresses due to global warming adversely affects the yield and growth of agricultural crops (Atkinson et al., 2013; Suzuki et al., 2014; Pandey et al., 2015). Different abiotic stress conditions such as heat, cold, salinity and drought indirectly affect the crop plants by favoring the spread of insects, pathogens and weeds (McDonald et al., 2009; Peters et al., 2014). These stresses also directly affect the crop plants by decreasing photosynthesis and whole plant growth, stomatal closure and wilting (Sanchez et al., 2002). Additionally, abiotic stresses such as drought boost the weeds competition with crops as numerous weedy plants show enhanced water use efficiency than crop plants (Valerio et al., 2013). Among these abiotic stresses, drought stress is one of the most damaging factors that causes significant loss of crop yield (Amelework et al., 2015; Boyer and Westgate, 2004). Drought is the most edaphic stress that damages cellular homeostasis and hinders the plant growth (Dai 2011; Pandey and Shukla, 2015). Water demand for irrigation is continuously increasing while there was a drastic reduction in the availability of water, this condition is more critical in semi-arid and arid conditions (Rostamza et al., 2011). Drought is the state of water shortage due to abnormal rainfall for a prolonged period of time. Agriculture drought is the lack of sufficient moisture essential for normal crop growth and development to complete life cycle. In general, drought stress at any growth stage showed detrimental and negative effects on development and growth of crop, depending upon the crop growth stage and severity of drought stress. Drought affects the biochemical, morphological and physiological processes in crop plants. Significant consequences of drought on crop include a reduction in cell expansion and division rate, impaired germination, reduction in leaf size, disturbed stomata oscillation, decreased chlorophyll contents. The Earth is a water-scarce planet; feeding more people by using less water is the major goal (Foley et al., 2011). To cop this drought challenge, crops having high adaptability in drier regions should be used. Among these, sorghum is one of the best choices grown for feed, food, fuel and fiber (Paterson et al., 2009; Qadir et al., 2015). Sorghum (Sorghum bicolor L.), also known as sorgo, chari or jawar, is an important summer forage crop of Physio-biochemical responses and defning selection criteria for drought tolerance in Sorghum bicolor Masood Qadir 1 , Amir Bibi 1 , Hafeez Ahmad Sadaqat 1 , Faisal Saeed Awan 2 1 Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Punjab, Pakistan. 38000 2 Centre of Agricultural Biochemistry and Biotechnology, University of Agriculture, Faisalabad, Punjab, Pakistan. 38000 * Corresponding author: Masood Qadir Department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, Punjab, Pakistan. 38000 Cell # 00923017935415, E-mail: masoodpbg@yahoo.com KeyWords Cytoplasmic male sterile, traits, variability, multivariate, water potential and association Abstract Forty cytoplasmic male sterile (CMS) sorghum lines were evaluated for different physiological and biochemical traits under drought stress. Considerable genetic variability was found among all physio-biochemical traits i.e. water potential (Ψ w), stomatal conductance (g s ), photosynthetic efficiency, acid detergent fiber (ADF), neutral detergent fiber (NDF), ash and sugar contents. Results indicated that ash contents were found to be most adver- sely affected by drought stress followed by sugar contents and stomatal conductance respectively. However, the values of crude protein, acid detergent fiber (ADF) and neutral detergent fiber (NDF) were observed to be incre- ase under stress condition. Principal component analysis (PCA) was applied to recognize drought tolerant lines. Selection criteria was based upon findings of correlation analysis among all studied traits. The positive association of water potential, stomatal conductance and photosynthetic efficiency with desirable traits viz. ash and sugar contents; and NDF association with undesirable traits viz. ADF and NDF revealed a way forward to design future breeding programs of sorghum crop under the prevailing scenario of climate change.