Diversity in Fruit Morphology and Nutritional Composition of Juglans mandshurica Maxim in Northeast China

High-yield hybrid breeding of Camellia oleifolia based on ISSR molecular markers

BACKGROUND

C. Oleifera is among the world's largest four woody plants known for their edible oil production, yet the contribution rate of improved varieties is less than 20%. The species traditional breeding is lengthy cycle (20-30 years), occupation of land resources, high labor cost, and low accuracy and efficiency, which can be enhanced by molecular marker-assisted selection. However, the lack of high-quality molecular markers hinders the species genetic analysis and molecular breeding.

RESULTS

Through quantitative traits characterization, genetic diversity assessment, and association studies, we generated a selection population with wide genetic diversity, and identified five excellent high-yield parental combinations associated with four reliable high-yield ISSR markers. Early selection criteria were determined based on kernel fresh weight and cultivated 1-year seedling height, aided by the identification of these 4 ISSR markers. Specific assignment of selected individuals as paternal and maternal parents was made to capitalize on their unique attributes.

CONCLUSIONS

Our results indicated that molecular markers-assisted breeding can effectively shorten, enhance selection accuracy and efficiency and facilitate the development of a new breeding system for C. oleifera.

Enrichment and Evaluation of Antitumor Properties of Total Flavonoids from Juglans mandshurica Maxim

Flavonoids are important secondary metabolites found in Juglans mandshurica Maxim., which is a precious reservoir of bioactive substances in China. To explore the antitumor actions of flavonoids (JMFs) from the waste branches of J. mandshurica, the following optimized purification parameters of JMFs by macroporous resins were first obtained. The loading concentration, flow rate, and loading volume of raw flavonoid extracts were 1.4 mg/mL, 2.4 BV/h, and 5 BV, respectively, and for desorption, 60% ethanol (4 BV) was selected to elute JMFs-loaded AB-8 resin at a flow rate of 2.4 BV/h. This adsorption behavior can be explained by the pseudo-second-order kinetic model and Langmuir isotherm model. Subsequently, JMFs were identified using Fourier transform infrared combined with high-performance liquid chromatography and tandem mass spectrometry, and a total of 156 flavonoids were identified. Furthermore, the inhibitory potential of JMFs on the proliferation, migration, and invasion of HepG2 cells was demonstrated. The results also show that exposure to JMFs induced apoptotic cell death, which might be associated with extrinsic and intrinsic pathways. Additionally, flow cytometry detection found that JMFs exposure triggered S phase arrest and the generation of reactive oxygen species in HepG2 cells. These findings suggest that the JMFs purified in this study represent great potential for the treatment of liver cancer.

Provenance and family variations in early growth of Manchurian walnut (Juglans mandshurica Maxim.) and selection of superior families

This study, conducted in China in November 2020, was aimed at exploring the variations in growth traits among different provenances and families as well as to select elite materials of Juglans mandshurica. Thus, seeds of 44 families from six J. mandshurica provenances in Heilongjiang and Jilin provinces were sown in the nursery and then transplanted out in the field. At the age of 5 years, seven growth traits were assessed, and a comprehensive analysis was conducted as well as selection of provenance and families. Analysis of variance revealed statistically significant (P < 0.01) differences in seven growth traits among different provenances and families, thereby justifying the pursuit of further breeding endeavors. The genetic coefficient of variation (GCV) for all traits ranged from 5.44% (branch angle) to 21.95% (tree height) whereas the phenotypic coefficient of variation (PCV) ranged from 13.74% (tapering) to 38.50% (branch number per node), indicating considerable variability across the traits. Further, all the studied traits except stem straightness degree, branch angle and branch number per node, showed high heritability (Tree height, ground diameter, mean crown width and tapering, over 0.7±0.073), indicating that the variation in these traits is primarily driven by genetic factors. Correlation analysis revealed a strong positive correlation (r > 0.8) between tree height and ground diameter (r = 0.86), tree height and mean crown width (r = 0.82), and ground diameter and mean crown width (r = 0.83). This suggests that these relationships can be employed for more precise predictions of the growth and morphological characteristics of trees, as well as the selection of superior materials. There was a strong correlation between temperature factors and growth traits. Based on the comprehensive scores in this study, Sanchazi was selected as elite provenance. Using the top-percentile selection criteria, SC1, SC8, DJC15, and DQ18 were selected as elite families. These selected families exhibit genetic gains of over 10% in tree height, ground diameter and mean crown width, signifying their significant potential in forestry for enhancing timber production and reducing production cycles, thereby contributing to sustainable forest management. In this study, the growth traits of J. mandshurica were found to exhibit stable variation, and there were correlations between these traits. The selected elite provenance and families of J. mandshurica showed faster growth, which is advantageous for the subsequent breeding and promotion of improved J. mandshurica varieties.

Genome-Wide Identification of AP2/ERF Superfamily Genes in Juglans mandshurica and Expression Analysis under Cold Stress

Juglans mandshurica has strong freezing resistance, surviving temperatures as low as -40 °C, making it an important freeze tolerant germplasm resource of the genus Juglans. APETALA2/ethylene responsive factor (AP2/ERF) is a plant-specific superfamily of transcription factors that regulates plant development, growth, and the response to biotic and abiotic stress. In this study, phylogenetic analysis was used to identify 184 AP2/ERF genes in the J. mandshurica genome, which were classified into five subfamilies (JmAP2, JmRAV, JmSoloist, JmDREB, and JmERF). A significant amount of discordance was observed in the 184 AP2/ERF genes distribution of J. mandshurica throughout its 16 chromosomes. Duplication was found in 14 tandem and 122 segmental gene pairs, which indicated that duplications may be the main reason for JmAP2/ERF family expansion. Gene structural analysis revealed that 64 JmAP2/ERF genes contained introns. Gene evolution analysis among Juglandaceae revealed that J. mandshurica is separated by 14.23 and 15 Mya from Juglans regia and Carya cathayensis, respectively. Based on promoter analysis in J. mandshurica, many cis-acting elements were discovered that are related to light, hormones, tissues, and stress response processes. Proteins that may contribute to cold resistance were selected for further analysis and were used to construct a cold regulatory network based on GO annotation and JmAP2/ERF protein interaction network analysis. Expression profiling using qRT-PCR showed that 14 JmAP2/ERF genes were involved in cold resistance, and that seven and five genes were significantly upregulated under cold stress in female flower buds and phloem tissues, respectively. This study provides new light on the role of the JmAP2/ERF gene in cold stress response, paving the way for further functional validation of JmAP2/ERF TFs and their application in the genetic improvement of Juglans and other tree species.

Genome-wide identification and expression analysis of the MADS-box gene family during female and male flower development in Juglans mandshurica

The MADS-box gene family plays a crucial role in multiple developmental processes of plants, especially in floral organ specification and the regulation of fruit development and ripening. Juglans mandshurica is a precious fruit material whose quality and yield are determined by floral organ development. The molecular mechanism of J. mandshurica female and male flower development depending on MADS-box genes remains unclear. In our study, 67 JmMADS genes were identified and unevenly distributed on 15 of 16 J. mandshurica chromosomes. These genes were divided into two types [type I (Mα, Mγ, Mδ) and type II (MIKC)]. The gene structure and motif analyses showed that most genes belonging to the same type had similar gene structures and conserved motifs. The analysis of syntenic relationships showed that MADS-box genes in J. mandshurica, J. sigillata, and J. regia exhibited the highest homology and great collinearity. Analysis of cis-acting elements showed that JmMADS gene promoter regions contained light, stress and hormone response cis-acting elements. The gene expression patterns demonstrated that 30 and 26 JmMADS genes were specifically expressed in the female and male flowers, respectively. In addition, 12 selected genes common to J. mandshurica female and male flowers were significantly upregulated at the mature stage and were used to validate the reliability of the transcriptome data using quantitative real-time PCR. This comprehensive and systematic analysis of J. mandshurica MADS-box genes lays a foundation for future studies on MADS-box gene family functions.