Root Characteristics of Black Beans. II. Morphological Differences Among Genotypes1

Abstract

Total root biomass of two black bean (Phaseolus vulgaris L.) cultivars, ‘Black Turtle Soup’ (BTS) and ‘Strain 39,’ and four black‐seeded lines (70001, 70002, 70003, and 70004) was partitioned into adventitious, basal, and taproot components at several growth stages under both greenhouse and field conditions. Basal root weights were significantly higher for the four lines in the field and for 70001 and 70002 in the greenhouse than for BTS and Strain 39. Genotypes did not differ for adventitious root weights in both environments. Taproot weights were higher for all the lines compared with BTS; and for 70001, 70003, and 70004 compared with Strain 39 in the field. Genotypes did not differ for taproot weights in the greenhouse.Stem, hypocotyl, and taproot diameters were significantly higher for all the lines than for the two cultivars in the field. Hypocotyl and stem diameters of all lines were higher than for the two cultivars, except for stem diameter of 70002 when compared with BTS in the greenhouse. Taproot diameters of 70001, 70002, and 70004 were significantly higher than for Strain 39 under greenhouse conditions. Basal root diameters (sum of individual basal root diameters) of the four lines were significantly higher than for BTS or Strain 39 in both experiments. Genotypes did^ot differ in the number of basal roots under field conditions.In the field, most root parameters increased up to the seed initiation stage, followed by a significant decrease or no further increase at the pod fill stage. Significant stage ✕ genotype interactions occurred for basal root diameter and hypocotyl diameter in the field and for taproot weight, stem, hypocotyl, and basal root diameters in the greenhouse. The erect plant type of the lines may be attributable to larger basal roots.