Water deficit is the most important abiotic stress factor in crop production. Evaluation of the response of different potato cultivars to water deficit stress is necessary to release cultivars for regions with water deficit. A split-plot experiment with three replications was carried out during 2005 and 2006. The main factor consisted of three levels of irrigation (irrigation after 25%, 35% and 50% discharge of the available water, i.e. normal conditions, mild stress and severe stress, respectively), and the split factor included seven potato cultivars (Agria, Savalan, Satina, Caesar, Kennebec, Marfona and Santé). Cultivars Savalan, Caesar and Kennebec had higher total and marketable tuber yield, water use efficiency, and values for stress tolerance indices than the other cultivars, both under mild and severe stress conditions. Cultivars Caesar and Kennebec were selected as tolerant cultivars; cultivars Savalan and Satina were identified as moderately tolerant cultivars whereas cultivars Agria, Marfona and Santé proved to be susceptible to water deficit.

This experiment performed according to the factorial design and on the base of completely randomized design in three replications in 2007. Factor A included four levels of osmotic pressure (0, -1, -2 and -3 bar) and factor B included seven advanced potato cultivars (Agria, Savalan (397007-9), Satina, Caesar, Kennebec, Marfona and Sante). The PEG 6000 was used for exerting the water deficiency stress on the plantlets. The attributes such as germinating ability and root producing was measured. In this stage the cultivar that produced the roots, had moved to the greenhouse. The plantlets were planted in soil bed with mixed of Punce and Biolan with 1:1 v/v. The applied experimental design was factorial on the base of completely randomized design in three replications. Factor A has four levels of osmotic pressure and factor B included seven advanced potato cultivars. After two months, was harvested the mini-tubers and the attributes was measured such as mini-tuber average size, mini-tubers weight and number per plant. The variance analysis results showed that significant difference between osmotic pressure levels, cultivars and their interaction as attributes mini-tubers number and weight per plant and mini-tubers average size in 1% probability. The Caesar and Savalan cultivars had the most number and weight of mini-tuber per plant in -1 bar and Caesar and Kennebec cultivars in -2 bar osmotic pressures. The MP, GMP, STI and MSTI selected Caesar as better cultivar in normal and stress conditions. Results of cluster analysis showed that cultivars grouped in three clusters. The first cluster included Agria, Sante and Marfona (susceptible cultivars), the second cluster Satina, Savalan and Kennebec (moderately tolerance cultivars) and the third cluster Caesar (tolerance cultivar).

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This experiment was done on the three potato cultivars [Agria (susceptible), Satina (semi-tolerant) and Ceaser (tolerant to water deficit)] and three irrigation treatments (after 30 mm evaporation from basin class A, after 60 mm evaporation + spraying by Potassium Humate, and after 60 mm evaporation from basin class A) for two locations in 2007. Experimental design was Split Plot with three replications. Potassium Humate spraying (250 mL ha(-1)) were done in three stages of emergence, before tuberization and during tuberization period. Combined analysis of variance showed that there were significant differences between locations, cultivars, irrigation treatments and location x cultivars interaction as effect on tuber yield. Comparison of means for irrigation treatments showed that spraying by Potassium Humate in stress condition induced increasing of tuber yield. Spraying by Potassium Humate in water deficit condition increased tuber yield up to 11.01 ton ha(-1). Ceaser had the highest tuber yield. It had higher tolerance to water deficit as well. Ceaser had a high potential in control and severe stress. Decrease in yield of Ceaser after 60 mm evaporation + spraying by Potassium Humate and after 60 mm evaporation from basin class A, relative to control (after 30 mm evaporation from basin class A) was 1.03 and 13.08 ton ha(-1) but for Satina was 7.83 and 16.61 ton ha(-1), respectively. Satina had the lowest Environmental Variance, Environmental Variance Coefficient, Finlay and Wilkinson's and Eberhart and Russell's model and was the most stable cultivar. Lin and Binns parameter showed that Ceaser and Satina were the most stable cultivars. Results of GMP, STI and MSTI were very considerable and Ceaser and Satina had a high yield in water stress and control conditions.

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The present research characterized yield and yield components of 42 wheat genotypes after terminal drought stress. The experiment was in twice replicated simple rectangular lattice design, conducted at irrigated and terminal stress conditions during 2006-2007. These study genotypes had significant differences for grain yield at level of 1%. Genotypes 4057, Viking/5/Gds/4.., Sabalan and 5041 respectively with 6.313, 6.159, 5.793 and 5.774 t ha(-1) had the highest yield and Gascogen has the lowest yield with 2.561 t ha(-1). Mean of total grain yield for under study genotypes was 5.628 t ha(-1) in non-stress and 3.305 t ha(-1) in drought stress conditions. Drought stress decreased amount of grain yield 2.323 t ha(-1) that was noticeable. Interaction of Genotype x environmental conditions was significant at probability level of 1% for grain yield. Yield of all genotypes in drought condition was lower than non-stress condition. Genotypes Viking/5/Gds/4/Anza/3/Pi.., Sabalan, 4061,4057 and 4041 had more yield in non-stress condition and MV17/Zrn, Sabalan, Saysonz and 4032 in stress condition. Stress intensity pay attention to total grain yield was 42%. Genotypes Viking/5/Gds/4/.. and Sabalan had high grain yield and was better than other genotypes and controls (Toos and Crosse Shahi), according to GMP, STI and MSTI. And had the most amount of stress tolerance index as compared with other genotypes confirms this subject. Correlation of yield with other traits was not significant in non-stress condition. In drought condition, correlation of grain yield with 1000 grain weight and total number of tillers per plant was positively significant. ANOVA showed significant differences between osmotic pressures for coleoptile length, between genotypes for mean and maximum coleoptile length and between interactions of genotypes x osmotic pressures for mean and maximum coleoptile length. Mean comparisons showed the highest total, mean and maximum coleoptile length in -7 bar PEG+I ml L(-1) potassium humate treatments. Genotypes Sardari and Sabalan had the highest amounts of total, mean and maximum coleoptile length. With due attention to interaction genotype x osmotic pressures, genotypes Sardari, Sabalan and 4057 in -7 bar PEG+1 ml L(-1) potassium humate had the most amounts of noted characters than others. In conditions of this experiment, potassium humate caused increase in tolerance rate of genotypes against drought stress.

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