Evaluation of common bean for root traits in relation to drought tolerance

Drought stress is a worldwide production constraint of common bean. The present study was undertaken to assess the response of common bean under drought in respect of root traits and biomass allocation in fifteen common bean genotypes at Regional Research station. Basal root growth angle was lowest in WB 216 (36.33) while as it was highest in Shalimar French Bean 1 (51.983). Tap root length was highest in WB 216 (14.333) while as it was lowest in SR1 (9.667). Similarly the basal root number was highest in WB 216 (13.667) and lowest in case of WB 83 (8.33). The total root length was highest in WB216 (71.467) and lowest in SR1 (20.00). The lateral root number was highest in WB 185 and lowest in SR 1 (12.333). The analysis of variance for the root traits revealed significant difference among all genotypes for all the traits except tap root length. There was a gradual decrease in both radical length and biomass under different concentrations of PEG treatment. However, most of the reduction took place at 20% PEG. Rooting depth was highest in WB 185 and lowest in Shalimar French Bean-1 under irrigated condition while as under drought condition it was highest in WB 216 and lowest in Shalimar French Bean 1. Similarly root biomass was highest under drought for WB 185 and lowest for WB 341 while as under irrigated condition, it was highest in Shalimar French Bean 1 and lowest for WB 83. Shoot biomass was highest in WB 83 under both irrigated and drought conditions while as it was lowest in Shalimar French Bean 1. Highest value for root to total biomass was recorded for Shalimar French Bean-1 under drought and WB 185 under irrigated conditions while as lowest was recorded for WB 83 under both conditions. Shoot to total biomass was highest in WB 83 under both conditions while as it was lowest for WB 216 in drought and Shalimar French Bean-1 under irrigated conditions. The highest proportion of roots at top under drought was for WB 83 while as lowest for WB 216 while as root biomass in bottom portion was highest under drought for WB 216 and lowest in WB 83. The root, leaf and stem dry weight was highest in WB 216 while as it was lowest in case of WB 341 for root and leaf dry weight and Shalimar French Bean 1 for stem dry weight. The pod dry weight was highest in case of WB 185 and lowest in case of WB 83. The relative proportion of root, leaf and shoot biomass to the total biomass was highest in case of WB 83, while as lowest value recorded for WB 185 for root and Shalimar French Bean 1 for leaf and shoot. The relative contribution of pods to total biomass was highest in case of Shalimar French Bean 1 (68.695%) followed by WB 185 (68.49%) and lowest in case of WB 83 (45.400%) and SR-1 (50.773%). Deep rooting trait helps plant explore greater soil volume and access more water, but greater biomass allocation to roots can be at the expense of grain production therefore it is imperative to breed plants for deep roots without additional biomass implications.