Relationships Among Yield, Canopy Temperature, and Root Architecture in Hard Winter Wheat.

Drought is among the most important environmental challenges that farmers face worldwide. This research aimed to explore the relationship between yield and morpho-physiological traits that can help breeders make selection decisions, as well as understand drought tolerance mechanisms in winter wheat. We used 30 hard winter wheat cultivars and advanced lines adapted to the Great Plains. Evaluation for grain yield was conducted at Greeley, CO in 2011-12 and in Fort Collins, CO in 2012-13 under two soil moisture levels (moisture stressed and fully irrigated). Canopy temperature was measured using an infrared thermometer during the grain filling stage. In 2011-12, roots were separated from 1-m deep soil cores, digitally scanned, and analyzed. In addition, a greenhouse experiment was conducted to study root architecture under water stress conditions in 1 m x 10 cm tubes. Genotypes differed for yield under both moisture treatments in both years. Canopy temperature also differed among genotypes. In the greenhouse study, genotypes differed significantly (P<0.05) for biomass, diameter, and length of the bottom root section, as well as total root biomass, diameter, and length. A significant correlation (r=0.757, P<0.05) was observed between average root diameter and water use efficiency (WUE). A significant negative correlation was observed between WUE and canopy temperature (r=-0.415, P<0.05). Genotypes varied significantly (P<0.05) for root length of top and middle sections and diameter of the bottom section from soil cores collected from the field. The Colorado cultivar ‘Byrd’ had the highest total root length in both the greenhouse and the field. Our results demonstrate variability for drought tolerance and root traits among Great Plains genotypes, but additional study is needed to determine the relationship between root traits, canopy temperature and dryland yield performance.