Variability in flooding tolerance, growth and leaf traits in a Populus deltoides intraspecific progeny

Climate change will increase the risk of flooding in several areas of the world where Populus deltoides Marshall (eastern cottonwood) is planted, so it would be desirable for this species to select for flooding tolerance. The aims of this work were to explore the variability in growth, leaf traits and flooding tolerance in an F1 full-sib intraspecific progeny of P. deltoides, to analyze the correlations of leaf and growth traits with flooding tolerance and to assess their suitability for use in breeding programs. Two-month-old parental clones and their progeny of 30 full-sib F1 genotypes were grown in pots and subjected to two treatments: (i) plants watered to field capacity (control) and (ii) plants flooded up to 10 cm above soil level for 35 days. Growth (height, diameter and biomass partition) and leaf traits (leaf size and number, specific leaf area, leaf senescence, abscission, stomatal conductance, carbon isotope discrimination, stomatal index) were measured. Flooding tolerance for each genotype was estimated as the ratio of the biomass of stressed plants to the biomass of control plants. Results showed segregation in terms of flooding tolerance in the F1 progeny. A significant genotype effect was found for leaf size and number, carbon isotopic discrimination and stomatal conductance, but it did not correlate with flooding tolerance. Height, diameter and root-to-shoot ratio had a positive phenotypic correlation with flooding tolerance, and there was a positive genetic correlation of height and diameter with biomass on both treatments. The narrow sense heritability values for the traits analyzed ranged from 0 to 0.56. We conclude that growth traits are more adequate than leaf traits for selection to increase flooding tolerance. A vigorous initial growth would increase flooding tolerance in young poplar plants.