Thirty-six provenances of Pinus densiflora were evaluated for stability and adaptability for height growth at 11 test sites in Korea. The data were obtained from measurements at age 6 and analyzed using linear regression model and AMMI (additive main effect and multiplicative interaction) model. There was significant provenance by site interaction effect (p < 0.011). The interaction term explained 7.1% of total variation. While the regression model accounted for 15.8% of GxE interaction term, the AMMI model accounted for 74.9% with four PCA values. Most of the provenances were not significantly different from the unity (b =1.0), except for Inje (1), Jungsun (4), Bongwha (5), Koryung (26), Hamyang (30) and Seoguipo (36). Adaptability of provenances to the test sites was estimated with mean height growth and first AMMI component scores (IPCA 1). Inje (1), Bongwha (5), Taean (20) and Seoguipo (36) were specifically adapted to the high yielding environments. Considering the first and second AMMI components (IPCA 1 and IPCA 2, respectively) scores, Whachun (2), Samchuk (10), Joongwon (14) and Buan (29) provenances were more stable than others. The implication of GxE interaction was discussed in view of seed transfer and delineation of seed zones.

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. . Tree height growth was significantly correlated with DBH growth whereas rank correlation of growth trait between sites was weak and non-significant. Highly significant differences in height, DBH growth and survival were observed among sites and between clones. The broad sense heritability was estimated separately in each site which was shown to be under moderate genetic control. Expected genetic response was estimated as a percentage of test mean in tree height and DBH growth after one generation of selection. The genetic response for tree height was expected to be 11.5 % in Java and 12.8 % in Kalimantan when the best 50% of superior clones were selected and used in a planting program. This result suggests that genetic improvement of growth traits through clone selection in P. canescens would be possible. The genetic gain could result in substantial returns if a large planting program would be developed.

Forest tree improvement is relatively a young science and its purpose is to provide guidance for the conservation, management and sustainable utilization of genetic resources of natural and managed forests. In South Korea, forest tree improvement programs started in 1956. The programs had two main aims: to guarantee the genetic origin of the forest reproductive materials used in afforestation and reforestation, and to develop genetically improved individuals and varieties of some commercially important trees. Since the launch of the forest tree improvement programs, biomass production has been the major improvement target, together with overall adaptability to different sites. Further improvement targets have recently been added, including wood quality traits, and more specific targets linked to adaptation to abiotic and biotic factors in response to new socioeconomic needs and global changes. Additionally, since the early 1970s, forest genetic resource conservation and forest fruit and nut tree breeding have progressed in South Korea. Molecular breeding techniques based on omics information are being developed to enhance the efficacy of selection and to accelerate forest tree breeding cycles. Genetic engineering, including gene editing, has also been applied, but is currently limited to research purposes. Forest tree improvement will be an integral part of the bioeconomy in securing the production of good quality raw materials in large quantities, and will play a significant role in sequestering carbon dioxide and decelerating climate change in the long term.

Background Larix kaempferi is one of the major timber species in Northeast Asia. Demand for the reforestation of the species is rising in South Korea due to an increase in large timber production and utilization. However, progeny trials for the species have not been explored, making it challenging to foster advanced generations of tree improvement. In the present study, genetic testing and selection for diameter growth were conducted using pedigree reconstruction and phenotypic spatial distribution analysis in a plantation of L. kaempferi. The aim of the present study was to select the superior larch individuals using the pedigree reconstruction and phenotypic spatial distribution to substitute progeny trials. The plantation of seed orchard crops was established in 1990 and one-hundred and eighty-eight trees were selected as the study material. Genetic variation was investigated first to validate its adequacy as breeding material. Genetic testing was carried out using a model considering pedigree information and spatial autoregression of the phenotypes. Results The expected heterozygosity of the mother trees and offspring were 0.672 and 0.681 presenting the corresponding level of genetic variation between two groups. The pedigree reconstruction using maternity analysis assigned one to six progenies to ninety-two candidate mothers. The accuracy of genetic testing was exceedingly increased with the animal model considering AR1 ⊗ AR1 structure compared to the animal model only. The estimated genetic variance of the former was 9.086 whereas that of the latter was 4.9E-5 for DBH. The predicted breeding values of the offspring for DBH were ranged from -5.937 cm to 5.655 cm and the estimated heritability of diameter growth was 0.344. Conclusions The genetic testing approach based on pedigree reconstruction and phenotypic spatial distribution analysis was considered a useful analytical scheme that could replace or supplement progeny trials.