Preliminary testing of eastern cottonwood clones

Broad-sense heritabilities were 0.44 to 0.47 for height, 0.24 to 0.28 for diameter, 0.26 to 0.29 for volume, 0.69 to 0.70 for specific gravity, 0.36 for fiber length, and 0.83 to 0.89 for resistance toMelampsora rust in a breeding population of 100 eastern cottonwood clones from central Mississippi grown for 1 year on Commerce loam and Sharkey clay in 10×10 triple lattice designs.The effect of site was statistically significant for growth andMelampsora rust, but not for wood properties. On the heterogeneous Commerce loam site, the lattice design was more efficient than randomized blocks for evaluating growth but not other characters. Both genetic and phenotypic correlations between characters were low and, with the exception of height x diameter (r p =0.52 to 0.65), of no practical significance in selection. Major variation in form was observed. Large-diameter cuttings elongated significantly faster than small ones through August, after which the effect of cutting diameter was not statistically significant.