Genetic evaluation and early selection of introduced Loblolly pine (Pinus taeda) families from the third breeding cycle

This study compared the growth status of different batches of introduced Loblolly pine (Pinus taeda) and conducted a comprehensive evaluation of the growth of 40 newly introduced Loblolly pine families to identify those with excellent early growth.

The study subjects were 40 loblolly pine families introduced and afforested in Yingde and Lechang, Guangdong. Traits such as tree height, diameter at breast height (DBH), and survival rate at 3 and 5 years were investigated. The results were compared with three test forests introduced in 1997 to assess the effectiveness of the current introduction. Variance analysis of tree height, DBH, and individual tree volume at two locations was conducted using R and ASReml software, and breeding values were calculated to select families with superior early growth.

1) Significant variations were observed among families of the introduced Loblolly pine (Pinus taeda) for all measured traits. In the Yingde trial forest, the mean tree height was 5.95 m, mean DBH was 14.00 cm, and mean individual volume was 0.044 9 m³. In the Lechang trial forest, these values were 6.09 m, 9.94 cm, and 0.024 2 m³, respectively—all exceeding those of the 1997 trial forest; 2) Based on breeding values for volume, four superior families were identified for early growth at the Yingde site: AGCLB-37, AGCLB-38, AGCLB-29, and AGM-025, with mean values of 6.15 m, 15.53 cm, and 0.0569 m³, outperforming the control group CK2. At the Lechang site, four families—AGM-225, AGM-005, AG-674, and AG-373—showed superior early growth, with means of 6.38 m 10.47 cm, and 0.027 6 m³, surpassing CK2.

The trial forests in Yingde and Lechang exhibited robust growth, with the introduced families demonstrating superior performance compared to those introduced in 1997. Four elite families were selected from each site (Yingde and Lechang), achieving volume-based genetic gains of 26.73% and 14.05%, respectively. Subsequent efforts should focus on selecting superior individual trees from these families. The chosen individuals can be used to enhance the second-generation breeding population and establish a third-generation breeding population, thereby enriching the genetic resources for Loblolly pine (Pinus taeda) improvement.