Great Plains Winter Wheat Varies for Root Length and Diameter under Drought Stress

Development of a deep, extensive root system is a drought adaptation mechanism that is beneficial for maintaining productivity under water scarcity in dryland cropping systems. To determine variation for root biomass, depth, length, and diameter and related physiological traits in winter wheat (Triticum aestivum L.), we conducted two greenhouse studies under drought stress. Study I evaluated 30 entries (cultivars and advanced lines) primarily from Colorado, and Study II included 30 entries from seven U.S. Great Plains states. Evaluations were conducted on pre-flowering plants in 1 m by 10 cm plastic tubes under greenhouse conditions. Tubes were weighed daily, and aboveground biomass (ABM) and root sections were collected aft er a 3-wk dry-down treatment. Roots were washed, scanned, and digitally analyzed. The Colorado entries differed significantly (P < 0.05) for estimated transpiration, ABM, average root diameter, total root length, and root length in most diameter classes. Great Plains entries differed significantly (P < 0.05) for ABM, stomatal conductance, water use efficiency, total root length, and root length for several diameter classes. Total root length correlated positively (P < 0.05) with leaf elongation rate and relative water content in Study I and negatively with average root diameter in Study II. There was no significant effect of the Rht-B1b or Rht-D1b alleles on root system growth of the Great Plains winter wheat germplasm. Variation in root traits can be exploited in breeding programs to develop plants with the best adapted root systems to withstand drought stress.