Evaluation of flooding tolerance in cuttings of Populus clones used for forestation at the Paraná River Delta, Argentina

We analysed the responses to flooding of 14 poplar clones used for forestation at the Paraná River Delta, Argentina. Some are commercial clones planted in the area, and others belong to a poplar breeding program from the National Institute of Agricultural Technology (INTA) in Argentina. Potted plants of 60 cm high growing in a greenhouse were watered (control) or submerged in water 10 cm above soil level (flooding treatment) for 35 d. Flooding reduced growth in height and diameter (combined as the volume index), total leaf area, photosynthesis (measured as electron transport rate) and stomatal conductance. In flooded plants, the number and area of newly formed leaves were also reduced. In some clones, flooding accelerated the senescence of basal leaves and induced the development of adventitious roots. A hierarchical cluster analysis was performed to classify the responses of the clones to flooding. Evaluating flooding tolerance as less reduction in growth and retention of a higher leaf area under flooding conditions, three groups with different degrees of flooding tolerance were identified: clone Alton was the most tolerant; clones A129-60, A106-60, SIA 22-85, Catfish 2 and 150-82 showed intermediate tolerance; and the remainder of the clones had low flooding tolerance. This information will be useful to recommend clones to be planted in flood-prone areas, and to select parents to be used in breeding programs