Genetic Yield Improvement in Soft Red Winter Wheat in the Eastern United States from 1919 to 2009

Periodic evaluation of breeding progress is necessary to assess genetic gains over time, and underlying traits responsible for yield gains can direct future breeding. This study was conducted to determine the rate and magnitude of yield progress in eastern soft red winter (SRW) wheat (Triticum aestivum L.) cultivars released from 1950 to 2009 relative to a historical cultivar Red May (1919). The effects of agronomic, morphological, and yield component traits on grain yield were studied in 50 widely grown historic and current cultivars in replicated yield trials at Warsaw, VA, in 2010 and 2011 and at Holland and Blacksburg, VA, in 2011. Genotype x environment interactions were significant (p < 0.01) for most traits. Linear regression models for yield were constructed for each environment, with r(2) values ranging from 0.62 to 0.76 among environments. The traits flag leaf angle, kernel weight, spikes per square meter, lodging, flowering date, harvest index, normalized difference vegetative index (NDVI), and green leaf retention, respectively, explained the most yield variation in multiple environments. The rate of genetic yield improvement ranged from 0.56% yr(-1) at Holland in 2011 to 1.4% yr(-1) at Blacksburg in 2011. Traits that consistently increased in magnitude over time were spikes per square meter, erect flag leaf angle, harvest index, seeds per spike, seeds per spikelet, and yield. Traits that decreased over the time period studied were flowering date and plant height.