Changes in stem and spike related traits resulting from breeding in Iranian wheat cultivars: associations with grain yield

Joudi M., Ahmadi A., Mohammadi V. (2017): Changes in stem and spike related traits resulting from breeding in Iranian wheat cultivars: associations with grain yield. Czech J. Genet. Plant Breed., 53: 107−113. This study investigated changes in stem and spike characteristics resulting from breeding in Iranian wheat cultivars, and their relationship with grain yield. Eighty-one wheat cultivars released between 1930 and 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 at Parsabad in the Moghan region during 2010–2011. Genetic improvement over time in specific stem weight (SSW) along with significant positive correlations between this trait and grain yield were observed at Karaj under DS conditions and at Parsabad, suggesting that SSW could be used as an indirect selection criterion for yield in these environments. Time-dependent changes in spike dry weight showed that the accumulation of photoassimilates in the spike from anthesis to 16 days after anthesis (16 DAA) was not changed by breeding. However, during the 16 DAA ‒ maturity phase, modern cultivars had more photoassimilates allocated to the spike than the old ones. This suggests that the sink is more limited during early grain growth than during the end of grain filling.