Genetic changes in agronomic and phenologic traits of Iranian wheat cultivars grown in different environmental conditions

Information on genetic gains in different traits of wheat is important in breeding cultivars with improved grain yield. Changes in agronomic and phenologic traits resulting from breeding in Iranian wheat cultivars were studied. Eighty one wheat cultivars released from 1930 to 2006 were examined under well watered (WW) and terminal drought stress (DS) conditions at Karaj during 2007–2008 and 2008–2009, and under WW conditions in the Moghan region during 2010–2011. Improvements in grain yield were 31 and 20 kg ha−1 y−1 in Karaj (under WW and DS conditions) and at Moghan, respectively. In response to DS, grain yield loss was less in modern than in old wheat cultivars, suggesting that, in line with grain yield improvement, breeding has increased the resistance of wheat to terminal DS. Significant genetic changes over time were found for HI, grain number per square meter and spike dry weight at anthesis in all conditions tested. No changes were observed for above–ground dry matter and 1,000 grain weight. Dates of booting and anthesis decreased significantly from old to modern cultivars, and the amount of decrease was more evident at Karaj. Karaj experiments showed that length of the grain filling period, the anthesis—maturity phase, was increased significantly by breeding. However, this trend was not found in the Moghan experiment. These findings indicate that there was an interaction between genetic gains in different traits and environmental conditions in which the genetic gains were studied.