Study and investigation on physiological indices related to drought tolerance in advanced durum wheat lines

This study was conducted with 18 advanced durum genotypes and two check cultivars, Zardak ( durum check) and Sardari ( Bread wheat check), under raifed and supplemental irrigation in field and also under stress ( polyethylene glycol) and non-stress ( water distilled ) conditions in laboratory in Sararood station in growing seasons 2004-5 and 2005-06. Some physiologic traits such as relative water content (RWC), relative water loss( RWL), chlorophyll fluorescence (CHF), percentage of relative injury (RI%), leaf water potential (LWP) and agronomic traits including plant height (PLH), days to heading (DHE) and maturity (DM), thousand kernel weight (TKW), flag length (FL), spike length (SL), peduncle length (Ped. L), ratio peduncle to PLH (Ped.L/PLH), grain yield, stress tolerance index (STI) and tolerance index (TOL) were measured. In laboratory, coleoptile&rsquos length (Col.L), rootlet length (Root. L), number of root (Root No.), promptness index under stress (PIS) and non-stress (PIN) and germination stress index (GSI) were studied. The genotypes were significantly varied based on analysis of variance and comparison mean for the studied agro-physiologic traits. In the both growing seasons, the genotypes No. 9, 15 and 19 had the highest grain yield under rainfed condition and the genotypes No. 13 and 16 for 2004-05 and the genotypes No. 8, 12 and 19 for 2005-06 had the highest yield performance under supplemental irrigation. The genotype No. 16 with the highest yield across environments had the highest STI and TOL whereas the genotype No. 8 with the lowest yield had the lowest TOL and relatively low STI. The results of path-coefficient analysis for grain yield under rain-fed condition showed that the traits of DHE, DM, FL, Ped.L/PLH, PLH, RWC, SL had positive direct effect on yield and the remining traits had negative direct effect. The genotype No. 19 had the highest cleoptile and rootlet length and for these two traits genotypes No. 6 and 17 were in lowest. The genotype No. 19 had the highest PIS and PIN and genotype No. 3 had the lowest. The genotypes No. 3, 9, 11, 14 and 20 had the higher GSI under stress than non-stress conditions. The STI as a field criterion had significan positive correlation with the traits of Root.L. and Root. No., which indicating selection based on Root. L. and Root.No. in laboratory condition may be useful and recommended for screening in field condition.