To study the relationship of phenology and physiological traits of rainfed wheat yield and yield components, 13 bread wheat (Triticum aestivum 1.) cultivars namely Atila, Atrak, Alborz, Inia, Bakonara, Pastoor, PRI, Tajan, Zagros, Falat, Khazar, Golestan and Vinak were evaluated under rainfed conditions during 1998 growing season. The experimental design was a randomized complete block one with four replicates. The results of the experiment revealed that improvements in grain yield were associated with increases in biological yield, harvest index, allocation efficiency, grain filling rate, grain number per unit area and grain number per spike. Days to physiological maturity and grain filling duration exhibited a negative correlation with grain yield. Traits such as days to anthesis, total biomass in anthesis and grain weight were not significantly related to grain yield.
)