Stay green character at grain filling ensures resistance against terminal drought in wheat

Water shortage is the main constraint limiting crop productivity across the globe especially when it occurs at reproductive and grain filling stages. This study was conducted to monitor the mechanisms of drought resistance, during reproductive stages (booting, heading anthesis and post-anthesis stages) by monitoring the stay green character, water use efficiency, grain filling rate, grain filling duration, grain yield and harvest index. Seeds of wheat cultivars C-591, Chakwal-50, Dharabi-2011, BARS-2009, Uqab-2000, Sehr-2006, Shafaq-2006, Faisalabad-2008, Lasani-2008 and Mairaj-2008 were sown in 10 kg soil filled pots on November 25, 2011. The drought stress was applied at the respective reproductive stage, which continued till maturity. Controlled plants were well-watered throughout the crop ontogeny. Pots were maintained at 70% water holding capacity (WHC; well watered) till booting stage and then managed drought stress was induced as per treatment maintaining 35% WHC (drought stress). Drought stress at all the stages significantly influenced the crop performance in all the tested cultivars. Severity of drought was more when it was imposed at booting and heading stages while was less devastating when imposed at anthesis and grain filling stages. Cultivars Chakwal-50 and Mairaj-2008 showed more stay gray character and took longer duration for grain filling, which resulted in the maintenance of higher grain weight and grain number per spike, grain yield and water use efficiency under stress conditions. In drought sensitive cultivars (BARS-2009, Uqab-2000), the drought increased the grain filling rate, while grain filling duration was substantially decreased. To conclude, stay green character, grain filling rate and duration under drought stress may be used as selection criteria for developing and/or screening wheat cultivars for drought resistance at reproductive stages.