SCREENING OF MAIZE (ZEA MAYS L.) GENOTYPES FOR DROUGHT TOLERANCE USING PHOTOSYNTHETIC PIGMENTS AND ANTI-OXIDATIVE ENZYMES AS SELECTION CRITERIA

The present study was conducted to screen the drought tolerance in some promising maize genotypes viz. FH-1285, FH-949, FH-1292, FH-985, FH-1046, FH-1257, FH-922, FH-988, FH-1137 obtained from Ayub Agricultural Research Institute (AARI), and, Yousafwala hybrid, 3025w/6129, SWL-539516, YSC-15, P1543/2567600 developed by Maize Research Institute, Yousafwala, Sahiwal, Pakistan. The experiment was laid out in a Completely Randomized Design (CRD) with three replicates. Drought was applied at three leaf stage by maintaining three levels of irrigation i.e.100% field capacity (full watering), 70% field capacity (mild drought stress) and 40% field capacity (severe drought stress). After 50 days of maintaining drought, plant sample was collected to record the growth and physio-biochemical parameters i.e. concentration of photosynthetic pigments, (Chl. a, Chl. b, total chl. and carotenoid content), anti-oxidative enzymes (SOD, POD, and CAT) and total soluble proteins. Drought stress severely hampered growth attributes that was clearly linked to a concurrent decrease in concentration of photosynthetic pigments at both mild and in particular at severe drought stress. Genotypes Yousafwala hybrid, P3164w/2403481 and FH-1137 showed less decrease in all growth parameters at both mild and severe drought levels indicating their resistant nature, whereas, genotypes FH-922, FH-985, FH-949 and FH-1257 were drought sensitive as they showed more than 50% growth reduction under severe drought stress. Genotypes P1543/2567600, YSC-15, FH-949 and FH-949 were considered moderately tolerant as they showed less decrease in growth parameters under mild drought conditions (70% field capacity), but under severe drought conditions (40% field capacity) a greater decrease in growth was recorded in the same genotypes. Antioxidant enzymes i.e. SOD, POD and CAT activity increased at both drought levels (70% and 40% field capacity) as compared to control plants (100% field capacity) accompanied by a concurrent increase in total soluble proteins in the genotypes Yousafwala hybrid, FH-1257, 3025w/6129, SWL-539516 and P3164w/2403481. Cluster analysis grouped the genotypes in distinct clusters indicating similarities among the various genotypes regarding their resistance to drought stress. The drought tolerant genotypes Yousafwala hybrid, P3164w/2403481 and FH-1137 are recommended for cultivation and improved crop yield in water deficit areas.