To better understand the genetic control of resin yield, growth traits and morphologic traits for Pinus elliottii families, genetic relationships among these traits were examined in three 27-year-old progeny trials located in Jingdezhen, Jian and Ganzhou, Jiangxi Province, China. In total, 3695 trees from 112 families were assessed at the three sites. Significant site, family and family × site effects were found for resin yield, growth traits and morphologic traits. Resin yield and growth traits were found to be under moderate genetic control for the three sites combined, with family heritability and individual narrow-sense heritability ranging from 0.41 to 0.55 and 0.11 to 0.27, respectively. The coefficient of genotypic variation (CV_G) of stem volume (SV) and crown surface area (CSA) were higher than those of other traits at each site. Genetic correlation estimates indicated that selection for growth traits might lead to a large increment in resin yield (RY), and most morphologic traits had moderate to strong correlations with growth traits at each individual site. One possible strategy in tree breeding would be to maximize resin production through selection for growth traits.

Malania oleifera Chun et S.K. Lee is an endangered woody oil tree that produces nervonic acid, which is closely related to brain development. The phenotypic variation and diversity in some representative traits in natural populations are poorly understood. To investigate phenotypic variation, diversity and their relationship with geoclimatic factors, we evaluated 21 traits of 97 sampled individuals from seven natural populations. Coefficient of variation for 21 traits widely ranged from 0.05 (shape index of fruit) to 0.62 (water content of dry kernel), with an average of 0.18. The Shannon–Wiener indices ranged from 1.91 (water content of dry kernel) to 2.06 (leaf length and leaf width), with an average of 1.94. The variation of 20 traits was significantly influenced by the population effect (p < 0.05). The 21 traits were reduced to six principal components, which collectively accounted for 86.64% of the total phenotypic variation. The seven population was mainly divided into two groups: Group I, which included four populations distributed throughout the southern region and having wider and shorter leaves, larger fruit transverse diameters, and higher content of fatty acid and nervonic acid in the kernel, and Group II included the left populations with relative opposite characteristics to those in Group I. Trees with shorter leaves tend to produce oblate shape and heavier dried kernel, yielding more fatty acid and nervonic acids, and population-level pairwise kernel morphological distance were positively correlated with fatty acid distance (Mantel r = 0.39, p < 0.05). Annual average humidity was strongly positively correlated with leaf index (length/width, r = 0.78) but had a negative correlation with the kernel dry weight (r = −0.84). The shape of the kernel gradually altered from oblate to globose as longitude and rainfall increased. The environment became colder as latitude increased, resulting in a steady decrease in fatty acid content. No significant isolation by climatic and geographical distance was found for morphological and fatty acid variability. These results can have an important implication for genetic improvement, diversity conservation and resource management of the species in the future.

Malania oleifera Chun et S.K. Lee is a woody oil tree species and is rich in nervonic acid, which is associated with brain development. The variation in fatty acid composition and its response to environmental factors in natural populations has not been well studied. A total of 97 mature fruiting individuals were sampled from seven natural populations in Guangxi and Yunnan provinces, China. The fatty acid content (FAC) was 53.85%. Thirteen fatty acid components were identified. Nervonic acid (NVA), octadecenoic acid (OEA) and docosenoic acid (DSA) were the top three, averaging 45.68%, 30.21% and 14.03% of the FAC, respectively; the saturated fatty acid and unsaturated fatty acid contents were 4.82% and 95.18%, respectively. Coefficients of variation were low to moderate (7.64-18.42%) and Shannon-Wiener indices were moderate to high (1.80–2.04) for FAC, NVA, OEA and DSA. Significant variation between populations was observed for all traits, explaining 62.83%, 40.54%, 21.98% and 32.85% of the variance for FAC, NVA, OEA and DSA, respectively. The strong collinearity among traits summarized them into three principal components. FAC was positively correlated with NVA and NVA was negatively correlated with OEA and DSA at both the population and phenotypic levels. This pattern was significantly divergent from those documented in tree species with low NVA yields. The production of FAC and NVA is facilitated by elevated temperatures and reduced relative humidity. These findings provide a foundation for genetic improvement, industrial exploitation, resource management, and sustainable development of this species.

To explore the radial variation in wood properties of slash pine (Pinus elliottii Engelm.) during its growth process and to achieve the early prediction of these properties, our study was carried out in three slash pine harvest-age plantations in Ganzhou, Jian, and Jingdezhen, Jiangxi province of South China. Wood core samples were collected from 360 sample trees from the three plantations. SilviScan technology was utilized to acquire wood property parameters, such as tangential fiber widths (TFWs), radial fiber widths (RFWs), fiber wall thickness (FWT), fiber coarseness (FC), microfibril angle (MFA), modulus of elasticity (MOE), wood density (WD) and ring width (RD). Subsequent systematic analysis focused on the phenotypic and radial variation patterns of wood properties, aiming to establish a clear boundary between juvenile and mature wood. Based on determining the boundary between juvenile and mature wood, a regression equation was used to establish the relationship between the properties of juvenile wood and the ring ages. This relationship was then extended to the mature wood section to predict the properties of mature wood. Our results indicated significant differences in wood properties across different locations. The coefficients of variation for RD and MOE were higher than other properties, suggesting a significant potential for selective breeding. Distinct radial variation patterns in wood properties from the pith to the bark were observed. The boundary between juvenile and mature wood was reached at the age of 22. The prediction models developed for each wood property showed high accuracy, with determination coefficients exceeding 0.87. Additionally, the relative and standard errors between the measured and predicted values were kept below 10.15%, indicating robust predictability. Mature wood exhibited greater strength compared to juvenile wood. The approach of using juvenile wood properties to predict those of mature wood is validated. This method provides a feasible avenue for the early prediction of wood properties in slash pine.

Esteya vermicola is the first recorded endoparasitic nematophagous fungus with high infectivity capacity, attacking the pinewood nematode Bursaphelenchus xylophilus which causes pine wilt disease. Endosymbionts are found in the cytoplasm of E. vermicola from various geographical areas. We sequenced the genome of endobacteria residing in E. vermicola to discover possible biological functions of these widespread endobacteria. Multilocus phylogenetic analyses showed that the endobacteria form a previously unidentified lineage sister to Phyllobacterium myrsinacearum species. The number of genes in the endobacterium was 4542, with 87.8% of the proteins having a known function. It contained a high proportion of repetitive sequences, as well as more Acyl-CoA synthetase genes and genes encoding the electron transport chain, compared with compared with plant-associated P. zundukense Tri 48 and P. myrsinacearum DSM 5893. Thus, this symbiotic bacterium is likely to be more efficient in regulating gene expression and energy release. Furthermore, the endobacteria in nematophagous fungi Esteya vermicola contained multiple nematicidal subtilase/subtilisin encoding genes, so it is likely that endobacteria cooperate with the host to kill nematodes.