evaluation of physiological indices, yield and its components as screening techniques for water deficit tolerance in oilseed rape cultivars

water deficit is an important factor limiting crop production worldwide. drought stress can be managed by improving the availability of soil moisture conserved and selecting drought tolerant genotypes. several physiological indices including stomatal conductance (kl), relative water content (rwc), leaf temperature (tl) and crop temperature stability (cts) along with yield, its components and seed glucosinolate content were measured in five oilseed rape genotypes of brassica napus l. (talayeh, fornax, okapi, regent cobra and slm046) under non-stress and water deficit conditions imposed from late flowering (80% flowering) to maturity in a loam soil at the research center for agriculture and natural resources of east azarbaijan, iran (462e, 3758n) over two successive years (2001-2003). according to the significant decrease of kl and rwc and significant increase of tl caused by water deficit in both years, it seems that, these indices could reflect the drought effects occurring from late flowering in oilseed rape crops. kl and tl values also differed significantly among genotypes and therefore these indices could be used to screen oilseed rape genotypes for tolerance against late season drought. water deficit significantly decreased the number of pods per plant and seed yield in talayeh and fornax. significant positive correlation was observed between these traits during both years (r=0.88 and 0.89, respectively). it seems that when water deficit occurs from late flowering, decreased seed yield mainly via decreasing number of pods per plant is observed in oilseed rape. okapi and slm046 showed lower tl value (30.6 and 29.7c, respectively), a higher kl value (0.350 and 0.355 cm s-1 respectively) and seed yield (5,241 and 5,245 kg ha-1, respectively) under the water deficit condition. okapi and slm046 are therefore more suitable for cultivating in areas with late season water deficit stress.