Cultivar-Irrigation Interactions in Shoot/Root Traits of 15 Wheat Varieties in Wintergarden Region.

In recent years, the acreage of winter wheat has increased significantly in the Wintergarden regions of southwest Texas, coinciding with the sustained drought and lack of irrigation water in the Edwards aquifer region. In addition to water shortage, leaf rust is also an important factor influencing photosynthesis, especially during the critical stages of flowering and early grain filling in April, when high temperature and high humidity conditions prevail. The aim of this study was to provide a better understanding of the linkages of shoot and root traits with grain yield in southwest Texas. The experiment started 2014 and repeated in 2015. Fifteen winter wheat varieties were planted in a conventionally tilled silty clay soil under three levels of irrigation management: Full irrigation (100% evapotranspiration replenishment), 70% and 50% of full irrigation. Sustained rainfall in 2015 prevented grain harvest; so only yield components will be available in 2015. In both 2014 and 2015, peak leaf area index and root length density and thickness at harvest (in 0-80 cm soil depth) were measured and related to grain yield (or yield components). In 2015, the severity of leaf rust infection on the flag leaves was also surveyed in early April. Results of 2014 indicate that within the 0-120 cm soil profile, roots were most thin (highest length density) at the 40-60 cm depth interval. Canopy architecture measurements indicated that leaves tended more vertical under wet conditions (100% and 75% ETc) compared with dry condition (50% Etc). Correlation analysis showed that, under dry condition, grain yield was limited by root length density, while under wet condition it was limited by leaf area index. The varieties that performed best under dry and wet conditions were identified. Data analysis is underway to quantify the rust infection rate through image analysis and relate it to yield performance.