Early rooting and flooding tolerance in cuttings from a Populus deltoides full-sib family under greenhouse conditions

Abstract

Eastern cottonwood (Populus deltoides Bartr. ex Marsh.) is an important forest tree, with elite genotypes propagated mainly as unrooted dormant cuttings. Several areas where P. deltoides is planted periodically experience flooding episodes. The aims of this work were to analyze the early rooting capability and flooding tolerance of a P. deltoides full-sib family, and to identify growth, wood, and leaf traits that correlate with flooding tolerance. We analyzed the early rooting capability of the parental genotypes and 30 clones from the F1 generation under greenhouse conditions. The rooting percentage of the cuttings ranged from 50% to 100%. There was a positive genetic correlation between shoot weight and root traits (number, biomass, and total length). In a separate experiment, 2-month-old plants growing in pots from the same genotypes were subjected to two treatments: watering (control) and flooding for 35 days. Most genotypes showed an intermediate flooding tolerance with respect to the parental clones. Height, diameter, growth rate, biomass, plant leaf area, leaf number, and leaf increase rate had a positive phenotypic correlation with flooding tolerance, while wood density did not. Height and diameter are traits recommended for selection because they correlate with flooding tolerance, are easy to measure, and have moderate to high narrow sense heritability.