Emir. J. Food Agric. 2015. 27 (2): 178-185 doi: 10.9755/ejfa.v27i2.19277 http://www.ejfa.info/ 178 REGULAR ARTICLE Physiological responses to drought in four developed Triticum aestivum groups P. Scotti-Campos 1* , J. N. Semedo 1 , I. P. Pais 1 , M. Oliveira 1 , J. Passarinho 1 , M. Santos 1 , A. S. Almeida 2 , A. R. Costa 2 , N. Pinheiro 2 , C. Bagorro 2 , J. Coco 2 , A. Costa 2 , J. Coutinho 2 and B. Maçãs 2 Unidade de Investigação em Biotecnologia e Recursos Genéticos, Inst. Nac. Inv. Agrária e Veterinária, I.P., 1 Qta Marquês, 2784-505 Oeiras / 2 Apartado 6, 7350-591 Elvas, Portugal Abstract Restricted water availability and yield reductions derived from climate changes have become a strong concern as regards fundamental crops, such as wheat. There is an increasing need to characterize germplasm diversity in order to highlight drought tolerant genotypes and to assist Portuguese wheat breeding programs. Bread wheat (Triticum aestivum) varieties were selected from four different evolutive and/or breeding groups: ancient landraces, traditional varieties, modern currently used and advanced lines. The aim of this work was to identify physiological traits that contribute to drought tolerance during grain filling period. Plants were cultivated in pots, under semi-controlled greenhouse conditions. Drought was imposed by withholding irrigation after anthesis. Well irrigated and water stressed plants were compared as regards leaf gas exchanges (net photosynthetic rate, Pn; leaf stomatal conductance, gs; transpiration, E), instantaneous water use efficiency (iWUE), membrane electrolyte leakage, osmotic potential and leaf pigments. Subsequently, plants were maintained under a controlled irrigation (droughted plants: 50% of the water given to fully irrigated controls) until harvest, to quantify yield. Pn and gs were significantly reduced by drought in all varieties. As regards membrane integrity ancient and traditional varieties presented lower membrane injury, what may reflect a higher protoplasmic tolerance to drought. More evolved varieties (modern and advanced) showed higher spike weight per plant and number of grains per spike, disregard the water regime. Under water deficit 1000 kernel weight was reduced in all varieties except in traditional Pirana, which also showed an increase in the number of spikes per plant. Higher membrane stability, increased pigments and lower osmotic potential under drought may underly such improved response to drought, pointing this variety as an interesting genetic resource for breeding purposes. Key words: Membrane integrity, Photosynthetic activity, Triticum aestivum, Water deficit, Yield Introduction In South Mediterranean regions drought periods associated to high temperatures, have become more frequent and strongly affect plants productivity. The lack of information and unpredictability of target environments, especially in the context of climate changes, is still the greatest obstacle to the improvement of wheat yield productivity (Reynolds et al., 2012). Bread wheat (Triticum aestivum) is a major crop in South Portugal, where it is exposed to low rainfall and heat stress at the end of the growing season (Maçãs, 1996; Almeida, 2007). Local rustic genotypes, generally more adapted to extreme environmental conditions, have been replaced by more productive varieties. There is a continuous need to characterize germplasm tolerance to drought to assist Portuguese wheat breeding programs in Alentejo (Coutinho et al., 2013). This important portuguese wheat producing region is also highly prone to desertification and water shortage (Santos et al., 2001). Drought induces stomatal closure, resulting in photosynthesis reductions (Campos et al., 1999; Chaves and Oliveira, 2004). Water shortage causes oxidative stress to the cells through reactive oxygen species formation, which result in damaged cellular structures (Blum and Ebercon, 1981), leading to cell decompartmentation and death. Membrane injury can be evaluated through increased electrolyte leakage (Campos and Pham Thi, 1997; Matos et al., 2002; Campos et al., 2003; Received 1 June 2014; Revised 15 July 2014; Accepted 26 July 2014; Published Online 1 February 2015 *Corresponding Author P. Scotti-Campos Unidade de Investigação em Biotecnologia e Recursos Genéticos, Inst. Nac. Inv. Agrária e Veterinária, I.P., Qta Marquês, 2784-505 Oeiras, Portugal Email: paula.scotti@iniav.pt