Trends in main agronomic traits and grain yield in wheat landraces and cultivars during the last decades in Iran

It is of great importance in breeding strategies to know the relationship between grain yield and main agronomic traits and understand the trend of changes in traits during breeding history. To meet these objectives, 313 Iranian wheat genotypes including 203 Iranian landraces and 110 Iranian cultivars were planted in an augmented design along with three check cultivars repeated in seven blocks in 2014 on the research field of Agronomy and Plant Breeding, University of Tehran. In order to increase accuracy and decrease environmental variation, the experiment has been replicated in three different location. Linear regression analysis between investigated characteristics and year of cultivar release and year of collection of landraces showed that the grain yield and thousand grain weight were significantly increased in both cultivars and landraces while spike weight was only significantly increased in the cultivars. Plant height and spike length were significantly decreased only in the cultivars during 74 years of breeding programs. No significant changes, however, was observed in the landraces. Although the number of grain/spike was known as the most important and effective traits on grain yield based on the results of correlation and path analyses, there was no any significant change for this trait during breeding programs. Since there were high phenotypic and genetic coefficient of variation for this trait, it could be one the most important traits in future breeding programs.