Progeny Test for the Open-pollinated Families of Loblolly Pine with Multiple Site

Fifty two open pollinated families of loblolly pine involved in a three site progeny test were analyzed on their growth traits at the age of 6 years.Extremely significant differences were found among sites,with the largest amount of growth in Fuyang,the high latitude site,and the least amount of growth in Suixi,the low latitude site.Growth differences among families and effect of family × site interaction were both significant.Therefore,different superior families should be selected for different forestaion ares.We selected 15 and 9 superior families respectively for Yingde and Fuyang.Result of the test provided a basis for directional seeds supply and roguing of the primary seed orchard.With the above mentioned selection rate,when seed from the superior clones were collected for suitable forestation area,the genetic gain of volume was estimated to be 5.4%～5.8%.if the primary seed orchard was rogued and these superior clones were preserved,then the genetic gain of volume would be doubled,amount to 10.8%～11.6%.