Assessing root traits associated with root rot resistance in common bean

Detecting differences in root architecture and growth patterns among common bean (Phaseolus vulgaris L.) genotypes may provide unique selection criteria for genetic resistance to Fusarium root rot. Genetic variation in root system architecture was quantified for 10 contrasting bean genotypes that represent four common bean classes (kidney, cranberry, black, and snap bean) under greenhouse conditions and under root rot disease pressure in the field. Genetic variation existed in root architecture among common bean classes and was highly significant under field conditions. Variation in root traits was minimal under environmentally controlled, greenhouse conditions. Results from the field evaluation suggest that a greater number of adventitious roots can contribute to root rot resistance, where the three most resistant genotypes accumulated large amounts of biomass in adventitious roots. In the field environment, total root system dry weight was correlated to fine (r = 0.74, P < 0.001) and intermediate (r = 0.66, P < 0.01) root classes. Plasticity of root system response was high, indicating the value of screening in the field environment. (C) 2003 Elsevier B.V. All rights reserved.