Journal of Food, Agriculture & Environment, Vol.7 (2), April 2009 339 Effects of water limitation on grain and oil yields of sesame cultivars Hamdollah Eskandari 1 , Saeid Zehtab-Salmasi 1 *, Kazem Ghassemi-Golezani 1 * and Mohammad Hussein Gharineh 2 1 Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Tabriz, Tabriz, Iran. 2 Department of Agronomy and Plant Breeding, Agricultural and Natural Resources University of Ramin, Mollasani, Iran. *e-mail: szehtabi@yahoo.com, golezani@gmail.com Received 13 January 2009, accepted 17 April 2009. Abstract Two field experiments were carried out in 2007 and 2008, in order to investigate the effects of water supply (I 1 , I 2 , I 3 and I 4 : irrigation after 150, 200, 250 and 300 mm evaporation from Class-A pan) on grain and oil yields of five sesame cultivars (Yellow Witte, TN 238 , TS 3 , Safiabadi and local cultivar of Ramhormoz). Experiments were arranged as split-plot based on randomized complete block design in four replications, with the irrigation levels in main plots and sesame cultivars in subplots. The results indicated that all traits except grain weight were significantly affected by irrigation regimes. Grains per plant, biological and grain yields, oil percentage and yield and protein yield decreased, while protein percentage increased with increasing water availability. Severe water stress (I 4 ) reduced the oil and protein yields by 38.18 and 10.77%, respectively. The extent of these reductions was related with the variations in grain yield and oil and protein percentages of sesame under different irrigation treatments. TS 3 was a superior cultivar under all irrigation treatments. Key words: Oil, protein, sesame, water supply, yield. www.world-food.net Journal of Food, Agriculture & Environment Vol.7 (2) : 339-342. 2009 WFL Publisher Science and Technology Meri-Rastilantie 3 B, FI-00980 Helsinki, Finland e-mail: info@world-food.net Introduction Plants are exposed to a multitude of natural biotic and abiotic stresses. Drought is a major abiotic stress that severely affects food production worldwide. In some locations, naturally available water supplies do not allow the production of maximum yield from irrigable lands. In other regions, water resources are limited, leading to insufficient irrigation. These examples highlight the need for deficit irrigation management for different crops 13 . In scheduling irrigation programs, methods based on pan evaporation have widespread usage due to their simple and easy application and low cost 15 . Studies have shown that there is a close relationship between plant water consumption and evaporation pan that can be used in irrigation scheduling for farmers 10 . Moreover, Class-A pan is commonly used in agriculture due to the fact that it is the most suitable system for determining relationships among plant, water and climate 12 . Sesame (Sesamum indicum L.) which is usually planted in arid and semi-arid regions of the world is very responsive to environmental conditions such as soil moisture which can affect its yield 12 . This important annual oilseed crop has been cultivated for centuries, particularly in the developing countries of Asia and Africa, for its high content of both excellent quality edible oil (42-54%) and protein (22- 25%) 6 . The irrigation regimes affect yield, oil and protein contents of sesame grains. Mensah et al. 14 reported that drought stress resulted in stunted growth and reduced seed yield of sesame. Hong et al. 9 indicated that drought stress during vegetative growth reduced grain yield of sesame and that the main factor in yield reduction was plant height. According to Kassab et al. 11 , grain yield of sesame was reduced by 28% due to water stress. El-Wakil and Gaafar 7 indicated that applying six irrigations to sesame crop without skipping anyone gave the highest values of yield, while application of five irrigations resulted in the significant yield reduction. Sesame grains typically have a greater yield of oil, compared with many other oil seeds. The composition of sesame grain is markedly influenced by genetic, climatic and agronomic factors and varies considerably within variety. Al-Kahtany 1 concluded that dark-colored grains generally have higher oil and lower protein content. Al-Palsan et al. 2 revealed that limited water supply increased protein and reduced oil percentage of sesame crop. The large part of the land area in Iran is either arid or semi-arid. Sesame is grown in these lands, where rainfall is not adequate and so limited irrigation is necessary for economic crop production. The response of sesame cultivars to water limitation is not properly investigated. Thus, this research was aimed to evaluate oil, protein and grain production of five sesame cultivars under different watering conditions. Materials and Methods Two field experiments were carried out during the two successive seasons of 2007 and 2008 in Ramhormoz, Iran (46º36´N, 31º16´E, altitude 150 m a.s.l). The soil texture of experimental site was silt