Evalution of drought resistance in bread wheat (Triticum aestium L.,) and durum (Triticum turgidum Var durum) cultivars under Darab Agro. Clima.e. Condition.

Due to limitation of precipitation and lack of its favorable distribution in Warm and dry southern areas of Iran, droughtness as an important abiotic stress causes a resistance genotyps is an effective way to prevent the droughtness undesirable impacts in area which water limitation is a main problem for wheat production. In order to evaluate some wheat genotypes drought resistance appearance, the present experiment was conducted at Darab Agricultural Research Station in three years, from 19998 to 2001. The treatment design was a factorial combination of amount of irrigation water as main plots and wheat genotyps as subplots in a split plot design. The main plots were arranged as a randomized completely blocks design with three replications. Ten CIMMYIT DERIVED Genotyps were considered as subplots including 1) 95ESWYT (97-98), 2) 65 ESWYT (97-98), 30 11 ESWYT (96-97), 4) 62 ESWYT (96-97), 5) 12 ESWYT (97-98), 6- 92 ESWYT (96-97), 7- MAYAN/NAC ( DARAB-2), 8- CHAMRAN (ATILLA-50-Y), 9- SHUWA/MALD, 10- CAUZ/OPATA/CAUZ and three moisture regimes applied as subplots including a) full irrigation based on water requirement of wheat in Darab region as non- stressed treatment, b) 75% of full irrigation as moderately stressed treatment and c) 50% of full irrigation as severely stressed treatment. Drought resistance was evaluated by following four drought indices: 1) Si= (1-ydi/ypi)/Di, 2) Tol=ypi-ydi, 3)Gmp=(ypiأydi)0.5, 4) Ym= (ypi+ydi)/2 Where ypi is the grain yield of each genotype in non- stressed moisture, ydi is the grain yield of each genotype in stressed moisture regime (moderate or severely stressed moisture regimes) and drought intensity or Di= 1- (yd/yp), where yd is the average of grain yield of all genotype in stressed moisture regims and yp is the average of grain yield of all genotype in non- stressed moisture regime. Results of the experiment showed that when 75% of full irrigation water (moderately water steress) applied, kernel weight, kernel spiklet-1, spiklet spike-1, spike m-2, grain yield, harvest index, biomass and plant height were decreased 8.4, 9.9, 6.7, 21.8, 6.7, 16.4 and 3.3 percent respectively in comparision with full irrigation meanwhile when 50% of full irrigation applied these parameters decreased 16.3, 22.1, 13.8, 40.7, 12.89, 32.2 and 8.1 respectively. CHAMRAN, 92 ESWYT (96-97), DARAB-2 and 65SWYT (97-98) significantly outyielded over other genotypes respectively. CHAMRAN grain yield was more than other genotypes in stressed moisture condition as well as non stressed moisture condition probably due to caring 1B/1R translocation from VERRY. High grain yield of CHAMRAN resulted from some high yield components, kernel spiklet-1 meanwhile the role of kernel weight was neglible. Besides having some superior yield components, producing more biomass and allocation of more drymatter to grain/ more HI was the specific characters of CHAMRAN for producing more grain yield. Although 65 ESWYT (97-98) was a superior genotype in full irrigation moisture regime, but low yielding one in stressed moisture conditions showing that its yield was unstable in deferent environment. In contrast with CHAMRAN, 11ESWYT (96-97) had low grian yield in both non-stressed and stressed moistures. Because high yielding genotypes such as CHAMRAN and 92ESWYT (96-97) were in the early maturity group and the low yielding genotypes such as 11ESWYT (96-97) was in the late maturity group, it seems that earliness was an efficient mechanism to allow the stressed plants escape from late season droughtness and high temperatures during grioain filling period in arid and semiaried areas. On the basis of all drought indices used in the present research, CHAMRAN was the most drought resistant genotype in moderately and severely drought stressed environments, and afterthan 92ESWYT (96-97) and 95ESWYT (97-98) were the high droughr resistant genotypes. Apparrently using of several drought indices (for example Si, GMP, YM and TOL used in the present investigation) are more valid rather than use of only one drought index to assessment of resistance/ sensitivity of different wheat genotype resistance. Generally it is concluded that there is enough genetic diversity in CIMMYT derived germplasms for selecting the drought resistant genotypes especially those early maturing genotypes caring 1B/1R translocation. Key words: drought stress, drought resistance, water irrigation, bread and durum wheat genotypes.