Temporal variation in phonological and agronomic traits of some irrigated facultative/winter bread wheat (Triticum aestivum L.) cultivars released between 1943 and 2011 in Iran

A field experiment was conducted at the Seed and Plant Improvement Institute Research Field Station in Karaj, Iran, during the 2009-10 and 2010-11 growing seasons to estimate genetic progress and the variation in penological and agronomic characteristics in 13 irrigated facultative/winter bread wheat (Triticum aestivum L.) cultivars released in Iran between 1943 and 2011. Trends of temporal variation of the traits measured revealed that grain yield and some related phonological and agronomic traits have increased in the more recently released cultivars. Thousand grain weight decreased slightly compared to older cultivars. Number of days to heading and anthesis decreased in new cultivars, butgrain-filling period and days to physiological maturity did not change. Spike length also increased but plant height decreased in more recently released cultivars. These changes may explain the increase in grain yield of newly released facultative/winter bread wheat cultivars.