Analysis of yield components, physiological and agronomic characters of different cultivars of winter wheat bred during different ages

A study was conducted to compare the performance of typical winter wheat cultivars certificated from the 1970s and latter, and now widely grown in the Hebei plain. The results show that, when all the cultivars from different ages are grown under the same conditions with adequate water and fertilizer supply, the new cultivars produce higher yield than the old ones. The unit area kernel numbers have a significant positive relationship with yield improvement. Kernel numbers per spike and 1000-grain weight do not change much between the old and new cultivars, and no significant relations exit between the two and yield increase. Harvest index is positively related to yield increase. It is observed that modern cultivars have higher harvest index and lower plant height than those of the old cultivars. Above-ground biomass of the cultivars developed after the 1990s dose not decrease with shortening plant height. Not much differences in wax content, SPAD value, and leaf water potential exist, but differences in specific leaf weight and ash contents are significant between the old and modern cultivars, and leaf ash content correlates with grain yield.