Abstract:

In this paper, two progeny trials of F₂ hybrid larch(Larix) in 14 years old from Qingshan Forest Farm, including the materials of Larix kaempferi×L.gmelinii, L.kaempferi×L.olgensis and L.gmelinii×L.kaempferi, were studied in order to know their separation in F₂ generation and growth heterosis in later stage. The result shows that there is no great separation in height growth of F₂ generation compared with F₁ generation, and the average of their variation coefficient only increases 2.3% and 5.8%. That means the hybrid larch is good in both of heterosis stability and growth potential. Therefore, establishing F₁ hybrid seed orchards is a good way to produce hybrid seeds with higher genetic gain in cold area of China. Also, some differences in height, diameter and volume for each family exist among 7 F₂ families, whose variation coefficient decreases along with the tree age, with 17.6%, 22.1%, 23.9% and 24.3% in 14, 8, 7 and 6 years old separately. This heterosis is also in existence among 15 hybrid families, although it is lower. The height growth of hybrid F₂ in 14 years old is 18.5% lower compared with that in 8 years old, and 10.3% lower compared with materials from seed orchards of L. olgensis, whose heterosis decreases 2.4%. Taking Xiaobeihu provenance as control, the growth potential of hybrid F₂ in 14 years old is obviously higher, whose growth in height, diameter and volume exceeds Xiaobeihu provenance in 28.1%、43.8% and 123.8%, and exceeds seed orchards of L. olgensis in 7.8%, 15.7% and 33.8%, whose heterosis is 7.1%, 4.1% and 12.1% respectively. Higher heritability can be seen among 7 hybrid families, who have gotten 10% genetic gains in height and diameter growth and 33% genetic gain in volume. For this reason, it is possible to use hybrid larch in second generation in forestry production.

Key words: larch(Larix), hybrid F₂, heterosis, age effect, hybrid separation