Historical Components of Soft Red Winter Wheat Grain Yield.

Forty-nine cultivars released between 1950 and 2009, and one from 1830, were grown in the 2009-2010 cropping season at Warsaw, VA, in 4.2 m² yield test plots.  The test was treated with growth regulator (trinexepac-ethyl). Two of four replications were treated with seed fungicide and insecticide (Baytan-Captan-Gaucho) as well as foliar fungicide (Tilt, Prosaro).

Data were collected on each cultivar for powdery mildew (Blumeria graminis f.sp. tritici) and leaf rust (Puccinia triticina) severity, seedling emergence, jointing date, tillers at Zadoks GS25, anthesis date, green area retention in the flag leaf, flag leaf length, width and area, ripening date, plant height, lodging, awn type, head length, peduncle length, tiller counts at maturity, grain yield, test weight, and 1000 kernel weight.  Harvest index, number of seeds per spikelet, spikelets per head, seeds per head, and floret fertility were assessed using 0.305 m whole plant samples harvested from three center rows within each plot. Genotypic analysis is underway for a genome wide association analysis.

Results from linear regression of the treated and untreated replications identified an eight variable model with an r² of 0.84. Positive effectors of yield included mature plant height, harvest index, seeds/spike, seeds/spikelet, flag leaf angle, and tillers with harvestable heads. Negative factors in the model were powdery mildew at heading, and leaf rust during grain-fill. The treated replications are of particular interest to identify genetic components of yield, and additional factors identified in a separate analysis were peduncle length and green flag leaf retention during grain-fill.  Three additional environments are being analyzed for the 2010-2011 cropping season.