When crops are seeded under contrasting environmental conditions, difference in temperatures may leave a major effect on photosynthesis and other metabolic process, leading to an impact on both biological and economic yield. In order to evaluate the influence of genotype and environment on phenology, yield components, seed quality and quantity and filling rate of safflower genotypes two field experiments were conducted in 2005 at Lavark Research Farm of the Isfahan University of Technology. Each experiment consisted of a 4-replicate RCBD and six safflower genotypes, Nebraska10, Arak 2811, Kouseh, S149,C111 and K12.While one experiment was seeded on March 18th (spring) and the other on June 21th (summer) 2005, data were subjected to a combined analysis of variances. Both number of days and GDD from seeding to seedling emergence, stem elongation, button formation and flowering were increased with summer seeding. Nebraska10 and Arak 2811 were later maturing compared to the rest of genotypes. The Leaf Area Index (LAI) and biological yield at button formation decreased with spring compared to summer seeding.The LAI and biological yield for Kouseh, S149, C111 and K12 were smaller than other genotypes. Seed filling rate was affected by seeding season; summer seeding due, apparently, to lower temperatures experienced during seed filling led to lower rates. While head/plant was not affected by planting season, the rest of yield components were decreased with summer seeding. The genotypes did not differ in seed filling rate, but differed in terms of head/plant, 100-seed weight, grain yield, oil percent and yield and protein percent and yield. Since Nebraska10 and Arak 2811 performed better in spring seeding and Kouseh in summer seeding, it could be concluded that the above genotypes may be recommended for safflower production under spring and summer seeding conditions of Isfahan , respectively.
