In Situ Imaging of Root System Architecture to Improve Drought Tolerance and Yield in Wheat.

Drought is one of the principal abiotic stresses limiting crop productivity. Breeding for improved root traits is an untapped source of crop improvement as certain root traits help to enhance crop productivity in resource-limited environments. However, the study of the root system has been mostly overlooked due to difficulties in root phenotyping, limited understanding of root system architecture (RSA) in relevant crops, and laborious field-based studies. Our studies sought to assay spatiotemporal root growth and development of spring and winter wheat using the CI-600 in situ root imager. First, we hypothesized that three drought tolerant spring wheat lines would show differing root traits from moderately drought tolerant elite wheat lines. We quantified root traits in six parental lines as well as a Hollis x Drysdale recombinant inbred line (RIL) in both greenhouse and dryland field studies. We can detect quantifiable differences in root traits amongst cultivars with negligible root growth after heading and anthesis. These results suggest root systems primarily develop during vegetative stages of growth, but slow or cease growth during reproductive phases such as grain filling. This study provides insight on the correlation of specific root traits with increased grain yield under drought conditions in spring wheat. Second, we hypothesized that near isogenic lines of winter wheat harboring Rht1 and Rht2 semi-dwarfing alleles would have altered RSA compared to standard lines. Limited studies of root growth in winter wheat has created a gap in understanding of root growth over the winter season. We observed little to no root growth in winter wheat cultivars from December to February, but found root growth resumed prior to above ground growth. We are currently quantifying root traits in two genetic backgrounds of winter wheat segregating for Rht1 and Rht2. These studies will help to provide precise information on RSA in field grown wheat cultivars throughout the growing season to identify specific, desirable traits for developing sustainable and drought-tolerant wheat varieties.