Procedures to screen root whorls

  1. Germinate the seeds. Six to eight seeds of each genotype are sterilized in 0.5% NaOCl for 1 minute to remove fungicide and other infections from the seed coat. Then seeds are wrapped in paper rolls, placed in a beaker containing 500 ml of 0.5 mM CaSO4 solution. Then, the beaker is placed in a germination chamber (incubator) at 28 ° Celsius for three days in the dark.
  2. On the third day, seeds are evaluated for root whorls. The number of root whorls is determined by counting basal root 'rings' coming from the tissue located between shoot and root tissues in the seedling.
  3. The number of 'rings' in the seedling is the number of root whorls. Then, total number of basal roots is determined, by counting the basal roots coming from each root whorls. Usually, total number of basal roots in plants is directly proportional to the number of root whorls. In common beans, the number of root whorls varies from 1 to 5, depending on the genotype.
Figure 1. Common bean genotype with 2 root whorls
Figure 2. Common bean genotype with 3 root whorls
Figure 3. Common bean genotype with 4 whorls, 14 basal roots