“…The ratio of variable fluorescence (F v ) to maximum fluorescence (F m ) is used to estimate the potential quantum efficiency of photosystem (PS) II maximum efficiency under abiotic stress conditions (Sayed, 2003;Rachmilevitch, 2006). This technique has been used as one of the stress-tolerance screening tools in different crop species including wheat (Yang et al, 2007;Kumar et al, 2012;Maulana et al, 2018), sorghum (Sayyad-Amin et al, 2016;Sukumaran et al, 2016), rice (Oryza sativa L.) (Lone et al, 2019), barley (Hordeum vulgare L.) (Li et al, 2006), and maize (Zea mays L.) (Song et al, 2018). Generally, a low F v /F m value indicates low photosynthetic efficiency, whereas greater F v /F m values under stress conditions show better tolerance to stress (Kumar et al, 2012).…”