The Early Selection of OPen Pollinated Families of Slash Pine

Analyses was conducted based on the data from a 9-year-old open-pollinated progeny test of P. elliottii in northwestern Zhejiang.The measurement of growth traits were taken annually for the first 5 years and at the 7th and 9th year,while the form traits were assessed visually at the 7th year.There were significant family variations in height,stem diameter,stem straightness and branch angle, and middle to high level family-mean heritabilities.The age trends of growth traits in family variances,juvenile-mature correlations and response to early selection were examined,5 to 7 years old was the optimum age for early indirect selection. Genetic gains were examined on the height,stemdiameter,stem straightness,and branch angle in selection indices. The results suggested that it is impossible to achieve substantial simultaneous improvement in both growth and form. Based on restricted indices constructed by using equal emphasis weights,three superior families were selected.