Abstract

The objective of this study was to investigate effects of natural variation in temperature and precipitation during grain filling on quantity and quality of three wheat cultivars (Pishtaz, Parsi and Sivand). The experiments were arranged as randomized complete block design with three replications in three field trials located in three provinces (Tehran, Isfahan and Fars) during the years 2011–15. Grain and biological yields for each cultivar were measured. Harvest index was calculated and 2 kg of grain from each wheat cultivar were used for quality traits (Protein content, wet gluten content and hectoliter weight). According to the results, a statistically significant correlation existed between grain and biological yields in four years of experiments. Biological yield is a significant factor affecting wheat yield. Increasing wheat yields were observed as coinciding with increasing biomass yields. There is no significant correlation between grain yield and total rainfall during the growing season, but there was a positive and significant correlation between grain yield and rainfall during grain filling. Another positive correlation was observed between hectoliter weights and rainfall during grain filling. Higher protein contents were observed in years with low yield levels. The wet gluten contents were parallel to the protein contents and as with the protein contents, increased in the years with low yield levels. Protein contents had a positive and significant correlation with mean temperature during grain filling. This indicates that with the increase in the average temperature during grain filling, the protein and gluten contents of the cultivars were increased.