[01] Biabani Abbas, Department of Plant Production, Faculty of Agriculture, Gonbad Kavous University, Gonbad - e - Kavous, Iran. [02] Golesorkhy Mohammad, Department of Plant Production, Faculty of Agriculture, Gonbad Kavous University, Gonbad - e - Kavous, Iran. [03] Sabouri Hosein, Department of Plant Production, Faculty of Agriculture, Gonbad Kavous University, Gonbad - e - Kavous, Iran. [04] Azarnia Mohsen, Department of Plant Production, Faculty of Agriculture, Gonbad Kavous University, Gonbad - e - Kavous, Iran.

Drought is a wide-spread problem seriously effects on rice (Oryza sativa L.) production and quality, also it is becoming an increasingly problem in many regions of the world. The objective of this study was to evaluate the ability of several selection indices to identify drought resistant cultivars (Shiroudi, Domsiah (local variety), Koral, IR70358-84-1-1, IR70358-84-1-2, WAB56-125, and IR80357-B-B12-3) under a variety of environmental conditions. Seven rice cultivars differing in yield performance were grown in separate experiments under rain-fed (non-irrigated) and irrigated conditions at the Research Farm of Gonbad Kavous University in 2010. A split-plot design was used with three replications. In flooding condition irrigation was conducted until maturity while in the drought condition, irrigation was watered to 40 days after transplantation then irrigation was discontinued. For rice plants survival and continued growth in drought conditions, irrigation was conducted a 14-day interval. Sowing was done in April and seedling density was 200 seeds per square meter. Six selection indices including stress susceptibility index (SSI), stress tolerance index (STI), tolerance (TOL), mean productivity (MP), geometric mean productivity (GMP), and harmonic mean (HM) were calculated based on yield and yield component under drought-stressed and irrigated conditions. The results showed that MP, GMP, STI and HM indices for yield and yield components were more effective in both drought-stressed and irrigated conditions. Selection of superior cultivar based on indices can be different for yield component. It is concluded that grain yield and filled grain number traits can be used to select superior cultivar under non stress and stress conditions.

Drought, Grain Yield, Resistance Indices, Rice, Yield Component

[01] Atlin GN. 2001. Breeding for Suboptimal Environments. In: Shu, F., Jaya, B. (Eds.), Increased Lowland Rice Production in the Mekong Region. Proceedings of the International Workshop, Vientiane, Laos, 30 October–2 November 2000. Aciar, Canberra, pp. 245–251. [02] Bansal KC, Sinha SK. 1991. Assessment of drought resistance in 20 accessions of Triticum aestivum and related species. Part I: total dry matter and grain yield stability. Euphytica. 56, 7–14. [03] Betran FJ, Beck D, Banziger M, Edmeades GO. 2003. Genetic analysis of inbred and hybrid grain yield under stress and nonstress environments in tropical maize. Crop Sci. 43, 807–817. [04] Bouslama M, Schapaugh WT. 1984. Stress tolerance in soybean. Part 1: evaluation of three screening techniques for heat and drought tolerance. Crop Sci. 24, 933–937. [05] Bruckner PL, Frohberg R. 1987. Stress tolerance and adaptation in spring wheat. Crop Sci. 27, 31–36. [06] Ceccarelli S. 1989. Wide adaptation. How wide? Euphytica 36, 265–273. [07] Ceccarelli, S., Grando, S., 1991. Selection environment and environmental sensitivity in barley. Euphytica. 57, 157–167. [08] Clarke JM, De Pauw RM, Townley-Smith TM. 1992. Evaluation of methods for quantification of drought tolerance in wheat. Crop Sci. 32, 728–732. [09] Clarke JM, Towenley-Smith TM, McCaig TN, Green DG. 1984. Growth analysis of spring wheat cultivars of varying drought resistance. Crop Sci. 24, 537–541. [10] Fernandez GCJ. 1992. Effective selection criteria for assessing stress tolerance. In: Kuo, C. G. (Ed.), Proceedings of the International Symposium on Adaptation of Vegetables and Other Food Crops in Temperature and Water Stress, Publication, Tainan, Taiwan. [11] Fischer RA, Maurer R. 1978. Drought resistance in spring wheat cultivars. Part 1: grain yield response. Aust. J. Agric. Res. 29, 897–912. [12] Garrity DP, O’Toole JC. 1994. Screening rice for drought resistance at the reproductive phase. Field Crops Res. 39, 99—110. [13] Guo PG, Baum M, Li, R. H., Grando S, Varshney RK, Valkoun J, Ceccarelli S, and Graner A. 2007. Differentially expressed genes between two barely cultivars contrasting in drought tolerance. Mol. Plant Breed. 5(2):181-183. [14] Henderson S A, Kamboonruang V, and Cooper M. 1995. Evaluation of a Glasshouse screening method to select for drought resistance in rain-fed lowland rice. In: Proceedings of the 1995 International Rice Research Institute, IRRI, Los Banos, Philippines. [15] Hohls T. 2001. Conditions under which selection for mean productivity, tolerance to environmental stress, or stability should be used to improve yield across a range of contrasting environments. Euphytica 120, 235–245. [16] Hossain ABS, Sears AG, Cox TS, Paulsen GM. 1990. Desiccation tolerance and its relationship to assimilate partitioning in winter wheat. Crop Sci. 30, 622–627. [17] Huang B. 2000. Role of root morphological and physiological character- istics in drought resistance of plants. In: Wilkinson, R. E. (Ed.), and Plant– Environment Interactions. Marcel Dekker Inc., New York, pp. 39–64. [18] Huke RE, Huke EH. 1997. Rice area by type of culture: South, Southeast, and East Asia. IRRI, Los Ban˜os, Philippines. [19] Kirigwi FM, van Ginkel M, Trethowan R, Sears RG, Rajaram S, Paulsen GM. 2004. Evaluation of selection strategies for wheat adaptation across water regimes. Euphytica 135, 361–371. [20] McCaig TN, Clarke JM. 1982. Seasonal changes in nonstructural carbohydrate levels of wheat and oats grown in semiarid environment. Crop Sci. 22, 963–970. [21] O’Toole J. C., Chang TT. 1979. Drought resistance in cereals-rice: a case study. In: Mussell H, Staples R, eds. Stress physiology in crop plants. John Wiley & Sons, Inc, 373-405. [22] Panthuwan G, Fokai S, Cooper M, Rajatasereekul S, O’Toole JC. 2002. Yield response of rice genotypes to different types of drought under rainfed lowlands. Part 1: grain yield and yield components. Field Crop Res. 41, 45–54. [23] Pantuwan G, Fukai S, Cooper M, Rajatasereekul S, O-Toole JC, and Basnayake J. 2004. Yield response of rice (Oryza sativa L.) genotypes to drought under rainfed lowland 4. Vegetative stage screening in the dry season. Field Crops Res. 89:281-297. [24] Pirdashti H, Sarvestani ZT, Nematzadch G, and Ismail A. 2004. Study of water stress effects in different growth stages on yield and yield components of different rice (Oryza sativa L.) cultivars. 4th Int. Crop Sci. Congress. [25] Rajaram S, Van Ginkle M. 2001. Mexico, 50 years of international wheat breeding. In: Bonjean AP, Angus WJ. (Eds.). The World Wheat Book: A History of Wheat Breeding. Lavoisier Publishing, Paris, France, pp. 579–604. [26] Rathjen AJ. 1994. The biological basis of genotype x environment interaction: its definition and management. In: Proceedings of the Seventh Assembly of the Wheat Breeding Society of Australia, Ade- laide, Australia. [27] Richards RA. 1996. Defining selection criteria to improve yield under drought. Plant Growth Regul. 20, 157–166. [28] Rosielle AA, Hamblin J. 1981. Theoretical aspects of selection for yield in stress and non-stress environment. Crop Sci. 21, 943–946. [29] Sio-Se Mardeh A, Ahmadi A, Poustini K, and Mohammadi V. 2006. Evaluation of drought resistance indices under various environmental conditions. Field Crop Res. 98: 222-229. [30] Van Ginkel M, Calhoun DS, Gebeyehu G, Miranda A, Tian-you C, Pargas Lara R, Trethowan RM, Sayre K, Crossa L, Rajaram S. 1998. Plant traits related to yield of wheat in early, late, or continuous drought conditions. Euphytica 100, 109–121.