http://agrobiol.sggw.waw.pl/cbcs Communications in Biometry and Crop Science Vol. 2, No. 1, 2007, pp. 8–16 International Journal of the Faculty of Agriculture and Biology, Warsaw University of Life Sciences, Poland REGULAR ARTICLE Sunflower (Helianthus annuus L.) germplasm evaluation for drought tolerance Saeed Rauf*, Hafeez A. Sadaqat Oilseeds Research Laboratory, Department of Plant Breeding & Genetics, University of Agriculture, Faisalabad-Pakistan. * Corresponding author: Saeed Rauf, E-mail: Saeedbreeder@hotmail.com CITATION: Rauf, S., Sadaqat, H.A. (2007). Sunflower (Helianthus annuus L.) germplasm evaluation for drought tolerance. Commun. Biometry Crop Sci. 2 (1), 8–16. Received: 26 September 2006, Accepted: 15 January 2007, Published online: 22 February 2007 © CBCS 2007 ABSTRACT Future climate changes are expected to increase risks of drought, which already represent the most common stress factor for sunflower (Helianthus annuus L.) production throughout the world. It is important, therefore, to evaluate genotypes for this stress. Our objective was to study yield and yield-related traits under irrigated and drought conditions in 56 sunflower genotypes of different origin and growth habit. A wide range of intraspecific genetic variability was present in sunflower, which could be used to develop new genotypes, more adapted to drought conditions. The highest level of tolerance was present in local genotypes. Among restorers, the highest level of tolerance was present in RL-57 (Pakistan), whereas an exotic restorer F-Yu-82 (Spain) showed the highest yield, along with high drought susceptibility index. Inbred line ORI-9/B (Pakistan) was identified as the most tolerant line combined with low yield potential, whereas AMES-10107 and AMES-10103 (China) were found to be moderately drought-tolerant lines with highest yield. Selection among segregating progeny from hybridization among lines with good drought tolerance with lines of good yield potential may lead to the development of superior inbred lines. Key Words: sunflower; drought; yield; drought susceptibility index. INTRODUCTION Drought stress is a worldwide production constraint of sunflower (Drgovic and Maksimovic, 1995). According to a report by USDA Agriculture Weather Facility (2005), oilseed production in 2005 was down 2% from 2004 due to drier than normal growing season. In Spain in particular, the sunflower crop suffered substantially from drought, decreasing production by 41%. Similarly in the Americas, drought was a key factor responsible for yield losses of up to 20% (Reddy et al., 2004). In Pakistan, sunflower acreage