Quantitative genetics of yield breeding for Populus short rotation culture. I. Dynamics of genetic control and selection model of yield traits

Abstract

Variation patterns and selection efficiencies for the three growth traits height, diameter, and volume were studied in two selected interspecific hybrid populations of eastern cottonwood (Populusdeltoides Bartr.): P. deltoides × Populussimonii Carr. and P. deltoides × Populusnigra L. Growth variables differed quite significantly (P < 0.01) among clones in each of the two hybrid populations, and they were more dominantly controlled by genetic factors than by environmental regimes. There were higher broad-sense heritablity levels for growth traits in this study than in other related studies. Genetic variances and broad-sense heritabilities for all traits markedly increased with stand development in the two hybrid populations; but the increasing rates with age of these two genetic parameters for diameter and volume were more rapid for P. deltoides × P. simonii hybridization than for P. deltoides × P. nigra hybridization. Selection of the best 5% of the clones from P. deltoides × P. simonii and the best 10% from P. deltoides × P. nigra produced mean 6th-year volume growth increases of 51 and 37%, respectively. Relative to P. deltoides, their high parent, the ratio of clonal heterosis of these selected hybrid clones was 5–23% for 6th-year volume. With different selection intensities, early selection of juvenile growth traits for the two populations, P. deltoides × P. simonii and P. deltoides × P. nigra, can also produce substantial indirect genetic gains for short rotation harvest traits. Further studies of Populus yield breeding and selection models were suggested.