GROWTH AND ARCHITECTURE OF SEEDLING ROOTS OF COMMON BEAN GENOTYPES

Common bean (Phaseolus vulgaris L.) is an important food crop in the tropics, where its productivity is often limited by edaphic stress. Root growth and architecture may be associated with genetic adaptation to edaphic stresses. Our objective was to evaluate the effect of genotype, time, and root type on various root growth and architectural parameters in bean seedlings. Seeds of four bean genotypes representing distinct growth habits (erect determinate, erect indeterminate, prostrate indeterminate, and climbing) were grown in containers of Oxisol soil in Cali, Colombia. Plants were harvested at 3-d intervals and roots divided into basal roots, taproot, and taproot laterals. Length, dry weight, and architecture (topological indices and fractal dimension) of each root class was determined until 14 d after planting. Significant genetic differences were observed in final root length, final root mass, number of basal roots, root growth rate, root elongation rate, number of root meristems, root topology, and root fractal di mension. Some association of shoot habit and root architecture was observed, with the climbing genotype HAB 229 having a more taproot dominated root system, and the prostrate genotype Carioca having a large number of root meristems. The nutrient efficient genotype Tostado had a vigorous, highly branched root system with numerous basal roots, while the nutrient-inefficient genotype Porrillo Sintetico had a smaller, less branched root system. Root type (basal, tap, taproot lateral) and plant age had significant effects on architectural parameters, which may compromise the utility of these parameters as selection criteria.