Variability in growth and cadmium accumulation capacity among willow hybrids and their parents: implications for yield-based selection of Cd-efficient cultivars.

Growth responses and cadmium (Cd) accumulation in willow cultivars help determine their potential in remediation of Cd-contaminated conditions. Seventeen willow cultivars, including hybrids and their parents, were grown in hydroponic conditions in a greenhouse, and their capacity for Cd tolerance and accumulation was compared. The results showed that shoot length, biomass production, and concentrations of photosynthetic pigments were significantly affected by 10 μM and 30 μM Cd treatments compared with the control. Biomass production varied across all cultivars and treatments, with maximum shoot dry weight in Owasco grown in 10 μM Cd (11.7 ± 4.5 g plant), and minimum in FC187 in 30 μM Cd (0.3 ± 0.1 g plant). Furthermore, shoot growth proved to be more sensitive to Cd than root growth. Cultivars tolerance to Cd stress varied as indicated by tolerance indices (TIs) ranging from 0.13 to 1.81 for shoots, and from 0.49 to 2.63 for roots. Cd accumulation also differed across treatments and cultivars, with average concentration of 217.49 μg. g in shoots and 478.47 μg. g in roots. Total amounts of Cd in all plant parts ranged from 38.98 to 4116.05 μg per plant, and cultivars SX64, Cicero, and Owasco exhibited a translocation factor (TF) of greater than 1. The correlation and path coefficient analyses demonstrated that shoot biomass reflected Cd transport and phytoextraction ability in selected willow cultivars. Our results also revealed that cultivars with higher leaf Cd concentration could be used as Cd-efficient parents to generate hybrids for Cd phytoextraction. Cultivars with higher biomass production translocated and accumulated more Cd in their aerial parts, and this finding will facilitate yield-based selection of candidates for Cd phytoextraction and for bioenergy production.