Received: 20 th Jan-2014 Revised: 24 th Feb-2014 Accepted: 28 th Feb-2014 Research article EVALUATION OF YIELD AND SOME MORPHOLOGICAL TRAITS OF WHEAT VARIETIES UNDER DROUGHT STRESS Peyman Aligholizadeh Moghadam * , Yousef Alaei and Elena Khabiri Young Researchers and Elite Club, Ardabil Branch, Islamic Azad University, Ardabil, Iran * Corresponding Author: Email: Peyman_moghadam67@yahoo.com ABSTRACT: Since the drought is known as one of the most essential factor limiting growth and crop production, an experiment was carried out to evaluate the yield components of 15 bread wheat genotypes in a randomized complete block design with three replications in Islamic Azad University Research Farm of Ardabil in 2011-12. In this study, traits such as yield per ha, plant height, spike length, number of grains per spike and seed weight were studied. Analysis of variance indicated a significant difference among genotypes for all traits were evaluated. The overall mean yield in genotypes was 2427.1 kg ha in this study. Genotype 12 with 3125 kg ha produced the higher grain yield and genotype 9 had the lowest (1650 kg ha) than other genotypes. Key words: wheat, drought stress, yield and yield components INTRODUCTION The cereals are the most important crop and supply the food of 70 percent of the people of Earth. They form the main base of nutrition and human survival. Wheat and rice provide nearly 60 percent of the energy needed to the man. And in general, more than 3.4 power and 1.2 protein needed human comes from grain [1]. As regards Iran is located in an arid and semiarid region in terms of weather, therefore, the risk of drought is threatening wheat. Hence, to achieve a sustainable self-sufficiency; drought resistant varieties should be used with high performance. In this regard, the identification and production of high yielding and resistant varieties has a special place in the country research. Drought is including the physical stress which is as the most important factor limiting growth and crop production and it is well known in many parts of the world and Iran [2]. Blum has stated that drought is multidimensional stresses that influence the plants at different levels of the organization [3]. Response to drought is complex in plants level, because it is a reflection from the combination of stress effects and relevant responses are at all low levels of organization in space and time. Siddique et al reported that drought is as the most important factors controlling the performance of products, almost "affect on all processes of plant growth [4]. Grain yield and related traits has a complex genetic control and multiple loci are related to quantitative traits responsible for it [5]. So that, Mohammadi et al (2008) for grain weight of barley, fifteen and for grain yield identified seven cases [6]. Grain yield and its sustainability in several areas where there are environmental stresses have been always used as an important criterion in the selection and presentation of data [7]. On the other hand, grain yield is a quantitative trait and is controlled by many genes. Also the heritability of this trait is low due to environmental effects and genotype-environment interaction; thus selection based on the yield may not be very effective to improve it [8]. Morphological characteristics were measured easily and with high precision and they have relatively high heritability, then selection based on this trait may be sure and rapid way for sieve plant communities and improve performance [9]. Emam et al (2007) from their studies concluded that, despite the favorable conditions until more than flowering, drought stress from flowering to grain filling has a significant effect on grain yield and can cause yield loss [10]. Therefore, in areas where there is risk of drought at the end of the growing season, using drought resistant varieties and adapted to the region which have high yield potential and little sensitivity to drought stress is advisable. Abhari et al (2006) found in their research that the grain yield sees the greatest damage in moisture stress condition [11]. And the reason is also reduction in the number of spikes per square meter, the number of grains per spike and grain weight. Grain weight is one of the key components of grain yield and it is determined by the rate and duration of grain filling. International Journal of Plant, Animal and Environmental Sciences Page: 121 Available online at www.ijpaes.com