We used spatial, global trend and post-blocking analysis to examine the effectiveness of a progeny trial in a tree breeding program for Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) on a hilly site with an environmental gradient from hill top to bottom. Diameter at breast height (DBH) and tree height data had significant spatial auto-correlations among rows and columns. Adding a firstorder separable autoregressive term more effectively modelled the spatial variation than did the incomplete block (IB) model used for the experimental design. The spatial model also accounted for effects of experimental design factors and greatly reduced residual variances. The spatial analysis relative to the IB analysis improved estimation of genetic parameters with the residual variance reduced 13 and 19% for DBH and tree height, respectively; heritability increased 35 and 51% for DBH and tree height, respectively; and genetic gain improved 3-5%. Fitting global trend and postblocking did not improve the analyses under IB model. The use of a spatial model or combined with a design model is recommended for forest genetic trials, particularly with global trend and local spatial variation of hilly sites.

Studying population genetic structure and diversity is crucial for the marker-assisted selection and breeding of coniferous tree species. In this study, using RAD-seq technology, we developed 343,644 high-quality single nucleotide polymorphism (SNP) markers to resolve the genetic diversity and population genetic structure of 233 Chinese fir selected individuals from the 4th cycle breeding program, representing different breeding generations and provenances. The genetic diversity of the 4th cycle breeding population was high with nucleotide diversity (Pi) of 0.003, and Ho and He of 0.215 and 0.233, respectively, indicating that the breeding population has a broad genetic base. The genetic differentiation level between the different breeding generations and different provenances was low (Fst < 0.05), with population structure analysis results dividing the 233 individuals into four subgroups. Each subgroup has a mixed branch with interpenetration and weak population structure, which might be related to breeding rather than provenance, with aggregation from the same source only being in the local branches. Our results provide a reference for further research on the marker-assisted selective breeding of Chinese fir and other coniferous trees.

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Cunninghamia lanceolata (Lamb.)Hook is an important economic timber tree in China. However, its genome characteristics have not been extensively assessed. To better understand its genome information, the bacterial artificial chromosome (BAC) library of chinese fir was constructed. A total of 422 BAC clones were selected and divided into 10 pools and sequenced, and with an average insert size of 121 kb, ranging from 97 to 145 kb. A total of 61,902,523 bp of reference sequences were sequenced and assembled, and based on an estimated genome size of 11.6 Gb for Chinese fir, the BAC library was estimated to have a total coverage of 0.53% genome equivalents. Bioinformatics analyses were also performed for repeated sequences, tRNAs, coding gene prediction, and functional annotation. The results of this study provide insights into the brief structure of the Chinese fir genome and has generated gene data that will facilitate molecular investigations on the mechanisms underlying tree growth.