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15 pages, 4822 KiB

Open AccessArticle

Genome-Wide Identification and Expression Profiling of the Response Regulator (RR) Gene Family in Pecan Reveals Its Possible Association with Callus Formation during Grafting

by Yan Zhang, Zhanhui Jia, Guoming Wang, Mengxin Hou, Min Zhai, Longjiao Hu, Jiping Xuan and Zhenghai Mo

Forests 2024, 15(3), 473; https://doi.org/10.3390/f15030473 - 03 Mar 2024

Viewed by 620

Abstract

Response regulator (RR) is the core component of cytokinin (CK) signaling, and it regulates the expression of numerous downstream CK-responsive genes. However, the knowledge regarding the pecan RR (CiRR) gene family is still limited. In this study, we first monitored trans-zeatin [...] Read more.

Response regulator (RR) is the core component of cytokinin (CK) signaling, and it regulates the expression of numerous downstream CK-responsive genes. However, the knowledge regarding the pecan RR (CiRR) gene family is still limited. In this study, we first monitored trans-zeatin riboside (tZR) content in the graft union 0, 7, 14, and 32 days after grafting and then conducted genome-wide analysis and expression profiling of the CiRR gene family using an available genome sequence and RNA-seq dataset, aiming to better understand the roles of CK during pecan grafting. The dynamic contents of tZR showed an increased trend during the specific period for both the scion and rootstock. There were 20 CiRRs in the pecan genome, including 12 type A CiRRs, 5 type B members, and 3 type C genes. All members contained a receiver domain and type B CiRRs possessed an additional Myb-like DNA-binding domain. Promoter analysis showed that the CiRR gene family contained cis-elements associated with growth and development, hormones, and stress. A total of 10 genes, including CiRR18/9/4a/14a/12c/5/12b/14b/2b/2a, were abundantly expressed in the samples of different tissues, drought stress, and kernel development. There were 12 genes (CiRR5/18/4a/12b/2b/12c/14b/2a/14a/4b/9/11a) showing active expressions during grafting, and weighted gene co-expression network analysis (WGCNA) grouped them into six modules. Among them, CiRR14a and CiRR12b were the hub genes for the turquoise and brown modules, respectively. Functional annotation indicated that the turquoise module was associated with gene transcription and translation, while the brown module was related to cell proliferation. Our results suggest that the CiRR gene family central to CK signaling is probably involved in callus formation during pecan grafting. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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19 pages, 2881 KiB

Open AccessArticle

Analysis of Genetic Diversity and Construction of a Core Collection of Ginkgo biloba Germplasm Using EST-SSR Markers

by Zhi Yao, Zhi Feng, Chunwen Wu, Longping Tang, Xiuzhong Wu, Dahua Chen, Qiye Wang, Kaifang Fan, Yiqiang Wang and Meng Li

Forests 2023, 14(11), 2155; https://doi.org/10.3390/f14112155 - 30 Oct 2023

Viewed by 994

Abstract

Understanding genetic diversity and population structure is essential for the conservation and utilization of germplasm. Ginkgo biloba L. is a medicinal, edible and ornamental tree species. Detailed knowledge of genetic variability and diversity in different Ginkgo germplasm resources is still scarce. In this [...] Read more.

Understanding genetic diversity and population structure is essential for the conservation and utilization of germplasm. Ginkgo biloba L. is a medicinal, edible and ornamental tree species. Detailed knowledge of genetic variability and diversity in different Ginkgo germplasm resources is still scarce. In this study, a total of 173,160 Expressed Sequence Tag Simple Sequences Repeat (EST-SSR) loci were derived from 43,073 Unigenes of the Ginkgo genome. A total of 43,731 pairs of specific primers were designed for the EST-SSR loci, with sequence lengths >20 bp, and 100 of the SSR primers were randomly selected. Among these, 20 EST-SSR markers were verified and used to assess the genetic diversity of 101 Ginkgo individuals collected from different regions. The average values for Shannon’s diversity index (I, 0.993), expected heterozygosity (0.566) and Nei’s genetic diversity index (H, 0.563) indicate a high level of genetic diversity of Ginkgo populations. Based on the EST-SSR markers, a core collection of Ginkgo germplasm comprising 27 genetic resources was constructed. The retention rates of the number of resources, the number of alleles, the number of effective alleles, the I index, the H index and the percentage of polymorphic loci of the constructed core collection are 26.73%, 95.29%, 103.43%, 102.25%, 102.91% and 100.00%, respectively. The molecular markers developed in this study are an effective tool for Ginkgo genetic diversity analysis and will facilitate the future breeding of this species. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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14 pages, 13129 KiB

Open AccessArticle

Collectible Cell Lines of Larix sibirica Obtained by Somatic Embryogenesis and Their Ability to Regenerate

by Iraida N. Tretyakova and Maria E. Park

Forests 2023, 14(9), 1920; https://doi.org/10.3390/f14091920 - 21 Sep 2023

Viewed by 756

Abstract

A protocol for the cultivation of Larix sibirica Ledeb. by somatic embryogenesis was developed (RF Patent No. 2456344, 2012). The L. sibirica collection consisted of 22 actively proliferating cell lines (CLs) obtained from immature zygotic embryos. The age of CLs ranged from 1 [...] Read more.

A protocol for the cultivation of Larix sibirica Ledeb. by somatic embryogenesis was developed (RF Patent No. 2456344, 2012). The L. sibirica collection consisted of 22 actively proliferating cell lines (CLs) obtained from immature zygotic embryos. The age of CLs ranged from 1 to 14 years. CLs differed in their growth intensity, embryonic productivity, hormonal balance, and genetic stability, as well as in their regenerative ability. In most proliferating CLs, the formation of globular somatic embryos continued for 2–4 years. Here, a number of CLs actively proliferated for 9–14 years or more. The formation of embryogenic cultures in L. sibirica is associated with the content of phytohormones and their localization in embryo cells. The cytogenetic studies revealed the genetic stability of young CLs (up to 1 year), in which the karyotype consisted of the diploid number of chromosomes (2n = 24). Genomic mutations were observed in the long-term proliferation of CLs. Individual CLs can maintain cytogenetic stability for many years; such CLs can successfully be used to preserve germplasm, obtain planting material, and for plantation reforestation. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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15 pages, 5340 KiB

Open AccessArticle

Flavonoid Metabolome-Based Active Ingredient Mining and Callus Induction in Catalpa bungei C. A. Mey

by Xiaofeng Zeng, Xiao Wang, Yanling Zeng, Jinbo Hou and Zhiming Liu

Forests 2023, 14(9), 1814; https://doi.org/10.3390/f14091814 - 05 Sep 2023

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Abstract

Catalpa bungei C. A. Mey is a unique and precious multi-purpose tree species that possesses great timber-related, ornamental and medicinal values. In this study, MS, N6 and DKW were used as basic media, and different concentrations of 6-BA and NAA were added for [...] Read more.

Catalpa bungei C. A. Mey is a unique and precious multi-purpose tree species that possesses great timber-related, ornamental and medicinal values. In this study, MS, N6 and DKW were used as basic media, and different concentrations of 6-BA and NAA were added for callus induction. The induction rate and total flavonoid content of callus tissue showed that the best callus induction medium was DKW + 2.0 mg·L⁻¹ 6-BA + 0.5–1.0 mg·L⁻¹ NAA. The leaves of different bark phenotypes of C. bungei C. A. Mey and the callus tissue extracted from young leaves of C. bungei C. A. Mey were used as experimental materials to construct metabolomic profiles of widely targeted flavonoids. Based on the metabolomic databases, the predominant flavonoids were screened from the callus tissues. Eight flavonoid metabolites increased in callus, and diosmetin-7-O-rutinoside (diosmin) was the flavonoid constituent with the shortest retention time, most efficient detection and best medicinal functions among these 8. The optimal medium for callus induction was supplemented with different concentrations of elicitors (salicylic acid SA and yeast extract YE). The optimal elicitor and the amount to be added were determined by analyzing the induction rate of callus, as well as the total contents of flavonoids and diosmin. The addition of SA and YE in appropriate amounts increased the total flavonoid content in the callus, but only the addition of YE promoted the formation of diosmin in the callus. The optimal medium formulation to promote the formation of callus was DKW + 2.0 mg·L⁻¹ 6-BA + 1.0 mg·L⁻¹ NAA + 30 g·L⁻¹ sucrose + 6.8 g·L⁻¹ agar + 10 μmol·L⁻¹ SA. The medium formulation to optimally increase the content of geraniol glucoside was DKW + 2.0 mg·L⁻¹ 6-BA + 1.0 mg·L⁻¹ NAA + 30 g·L⁻¹ sucrose + 6.8 g·L⁻¹ agar + 200 mg·L⁻¹ YE. The results of the present study will provide a scientific basis for the subsequent increase in the content of the active components of the suspension cells via the addition of elicitors, and for the production of diosmin in factory settings. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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15 pages, 2977 KiB

Open AccessArticle

The Effects of Homologous and Heterologous Grafting on the Growth of Gleditsia sinensis Scions

by Feng Xiao, Yang Zhao, Xiurong Wang and Xueyan Jian

Forests 2023, 14(9), 1777; https://doi.org/10.3390/f14091777 - 31 Aug 2023

Cited by 2 | Viewed by 674

Abstract

Gleditsia sinensis Lam. (Fam. Leguminosae; Gen.: Gleditsia) has various uses, including for medicinal, edible, chemical, and material purposes, and is widely distributed in China. However, the extent of graft compatibility and its impact on growth when using different Gleditsia species as [...] Read more.

Gleditsia sinensis Lam. (Fam. Leguminosae; Gen.: Gleditsia) has various uses, including for medicinal, edible, chemical, and material purposes, and is widely distributed in China. However, the extent of graft compatibility and its impact on growth when using different Gleditsia species as rootstocks for grafting G. sinensis scions is not yet clear. This study examined homologous and heterologous grafting between different Gleditsia species, measuring the survival rate, morphology, photosynthesis, physiology, and hormones of the grafted plants. The results showed that G. sinensis and other Gleditsia seedlings have survival rates of over 86%. The more distant the genetic relationship between species, the lower the grafting survival rate. The grafting of fast-growing G. fera as a rootstock increased the accumulation of photosynthetic products in the grafted plants, while the grafting of slow-growing G. microphylla as a rootstock slowed down the growth rate of the longitudinal extension of the leaves of the grafted plants. Heterografted rootstocks increased the contents of IPA, PP333, ACC, and DZ but decreased the levels of GA₄, iP, and SA hormones. Some hormone levels that can be highly expressed in seedlings were used as rootstocks, and the corresponding hormone levels in the grafted seedlings were still highly expressed. This study lays a material and theoretical basis for the development of new resources for the breeding and rootstock selection of G. sinensis. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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20 pages, 9307 KiB

Open AccessArticle

Mutant Bisexual and Wild Male Flowers Were Compared by Integrated Proteome and Transcriptome Analyses to Provide Insight into the Sex Conversion of Idesia polycarpa Maxim

by Huimin Wang, Zhi Li, Qifei Cai, Yanmei Wang, Xiaodong Geng, Shunfu Li, Lisha Fang, Shunyang Yao, Huiyun Li and Zhen Liu

Forests 2023, 14(9), 1737; https://doi.org/10.3390/f14091737 - 28 Aug 2023

Cited by 1 | Viewed by 868

Abstract

Idesia polycarpa is a dioecious tree; in field surveys, there are rare sex conversions in I. polycarpa individuals with bisexual flowers. To identify the molecular mechanisms underlying sex conversion in this species, an integrative analysis of the proteome and transcriptome profiles of I. [...] Read more.

Idesia polycarpa is a dioecious tree; in field surveys, there are rare sex conversions in I. polycarpa individuals with bisexual flowers. To identify the molecular mechanisms underlying sex conversion in this species, an integrative analysis of the proteome and transcriptome profiles of I. polycarpa male and bisexual flowers at key developmental stages was conducted in this study using isobaric tags for relative and absolute quantification and RNA-seq technology. A total of 15,003 proteins were identified; the differentially expressed proteins (DEPs) were enriched in metabolic pathways, biosynthesis of secondary metabolites, and flavonoid metabolism pathways in all comparison groups. A total of 290,442 unigenes were obtained; these were compared with seven databases, revealing 196,366 annotated unigenes. In general, the expression of proteins and genes tended to be positively correlated, with Spearman correlation coefficients in the ranges of 0.152–0.262 (all genes and all proteins) and 0.497–0.778 (DEPs and DEGs). The integrative analysis of DEPs and DEGs between male and bisexual flowers revealed that the most significantly enriched pathways were flavonoid pathways, metabolic pathways, and the biosynthesis of secondary metabolites. Finally, four co-expressed proteins and transcripts and one gene associated with the flavonoid biosynthesis pathway were screened out. The proteins identified were p-coumaroyl shikimate 3′-hydroxylase, and shikimate/quinate hydroxycinnamoyl transferase, and the gene was caffeoyl-CoA O-methyltransferase. The analysis has revealed key potential proteins and genes involved in sex conversion at the molecular level and has provided a basis for future investigations of artificial regulation of sex differentiation in I. polycarpa. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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14 pages, 2352 KiB

Open AccessArticle

Salt-Stress-Induced Ion Transport Contributes to K⁺/Na⁺ Homeostasis in Roots of Ping’ou Hybrid Hazelnut

by Da Luo, Fenghui Song, Mingyan Lu, Yanjiang Shi and Qinghua Ma

Forests 2023, 14(8), 1651; https://doi.org/10.3390/f14081651 - 15 Aug 2023

Viewed by 769

Abstract

Soil salinity is a worldwide problem that adversely affects plant growth and development. Soil salinization in Xinjiang of China is very serious. Ping’ou hybrid hazelnut, as an important ecological and economic tree species, as well as a salt-tolerant plant, has been grown in [...] Read more.

Soil salinity is a worldwide problem that adversely affects plant growth and development. Soil salinization in Xinjiang of China is very serious. Ping’ou hybrid hazelnut, as an important ecological and economic tree species, as well as a salt-tolerant plant, has been grown in Xinjiang for over 20 years. Understanding the salt-tolerance mechanism of Ping’ou hybrid hazelnut is of great significance for the breeding of salt-tolerant varieties and the rational utilization of salinized land. In this study, ‘Liaozhen 7’, a fine variety of Ping’ou hybrid hazelnut, was selected as test material, and seedlings were treated with 0 (control), 50, 100 and 200 mM NaCl. Subsequently, the pattern of NaCl-induced fluxes of Na⁺, K⁺ and H⁺ in the root meristematic zone and their response to ion transport inhibitors were studied using non-invasive micro-test technology (NMT). Different concentrations of NaCl stress significantly increased the Na⁺ concentration in roots, while K⁺ concentration decreased first and then increased with the increase of NaCl concentration. Meanwhile, NaCl stress induced a significant decline in K⁺/Na⁺ ratio. Control and 200 mM NaCl-induced Na⁺ and K⁺ fluxes in roots exhibited an outward efflux, whereas an inward flux was observed for H⁺. Under 200 mM NaCl stress, the average rates of net Na⁺ and K⁺ efflux, as well as H⁺ influx in roots were significantly increased, which were 11.6, 6.7 and 2.3 times higher than that of control, respectively. Furthermore, pharmacological experiments showed that 200 mM NaCl-induced Na⁺ efflux; H⁺ influx was significantly suppressed by amiloride, an inhibitor of plasma membrane (PM) Na⁺/H⁺ antiporter, and sodium vanadate, an inhibitor of PM H⁺-ATPase. Net Na⁺ efflux and H⁺ influx induced by NaCl decreased by 89.9% and 135.0%, respectively. The NaCl-induced Na⁺ efflux was mediated by a Na⁺/H⁺ antiporter using energy provided by PM H⁺-ATPase. The NaCl-induced K⁺ efflux was significantly restricted by tetraethylamine chloride, a K⁺ channel inhibitor, and promoted by sodium vanadate, which decreased by 111.2% and increased by 80.8%, respectively, indicating that K⁺ efflux was regulated by depolarization-activated outward-rectifying K⁺ channels and non-selective cation channels (NSCCs). In conclusion, NMT data revealed that NaCl stress up regulated the root Na⁺/H⁺ antiporter and H⁺ pump (an activity of PM Na⁺/H⁺ antiport system) of ‘Liaozhen 7’, which compelled the Na⁺/H⁺ exchange across the PM and restricted K⁺ loss via depolarization-activated K⁺ channels and NSCCs simultaneously, thereby maintaining the K⁺/Na⁺ homeostasis and higher salt tolerance. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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14 pages, 5485 KiB

Open AccessArticle

Enhancing the Cryopreservation System of Larch Embryogenic Culture by Optimizing Pre-Culture, Osmoprotectants, and Rapid Thawing

by Miaomiao Ma, Xuhui Wang, Chunyan Zhang, Solme Pak, Hongran Wu, Jingli Yang and Chenghao Li

Forests 2023, 14(8), 1621; https://doi.org/10.3390/f14081621 - 11 Aug 2023

Cited by 2 | Viewed by 1123

Abstract

Cryopreservation is considered the safe and efficient strategy for the long-term conservation of embryogenic cultures. The objective of this study was to cryopreserve the embryogenic tissues of hybrid larch to overcome the result raised by rapid growth rates of conifer embryogenic cultures necessitating [...] Read more.

Cryopreservation is considered the safe and efficient strategy for the long-term conservation of embryogenic cultures. The objective of this study was to cryopreserve the embryogenic tissues of hybrid larch to overcome the result raised by rapid growth rates of conifer embryogenic cultures necessitating frequent sub-culturing. We systematically evaluated several parameters, including the pre-culture method (liquid or solid), osmoprotectant type (DMSO, sucrose, or PEG6000), duration of cryoprotection (1–3 h), and thawing temperature (4 °C, 25 °C, or 40 °C). After one month of cryopreservation, we assessed the regeneration efficiency and maturation ability of both cryo-preserved and non-cryopreserved tissues. Our optimized protocol involves pre-culturing embryonic tissue on the solid medium with 0.4 M sorbitol for 48 h, followed by treatment with 10% DMSO, 0.4 M sucrose, and 15% PEG6000 for 1 h on ice, and immersion in liquid nitrogen with rapid thawing at 40 °C. Notably, the use of solid media during pre-culturing was crucial to enhancing the success rate of cryopreservation. Using protocol optimization, we achieved high embryogenic tissue survival rates of over 80% without affecting the ability of somatic embryogenesis. This work provides a comprehensive set of steps for routine cryopreservation of embryogenic tissues for long-term conservation in hybrid larch, along with sample protocols for cryopreservation of larch. The results demonstrate that vitrification is a reliable method for preserving embryogenic tissues of hybrid larch with broader implications for the cryopreservation of other plant species. Further optimization and standardization of protocols across different species would ensure the preservation of genetic diversity and facilitate future research in plant biotechnology that benefits human health, food security, and environmental sustainability. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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21 pages, 6647 KiB

Open AccessArticle

Phenotypic Differences of Leaves and Transcriptome Analysis of Fraxinus mandshurica × Fraxinus sogdiana F1 Variety

by Liming He, Jialin Yan, Han Lu, Wenlong Su, Shangzhu Gao, Yubin Wang, Yaguang Zhan and Fansuo Zeng

Forests 2023, 14(8), 1554; https://doi.org/10.3390/f14081554 - 29 Jul 2023

Viewed by 841

Abstract

Plant leaves, as one of the main organs of plants, have a crucial impact on plant development. In the hybrid F1 variety, one clone “1601” from the hybridization of Fraxinus mandshurica Rupr. × Fraxinus sogdiana Bunge was showed significant differences in leaf development [...] Read more.

Plant leaves, as one of the main organs of plants, have a crucial impact on plant development. In the hybrid F1 variety, one clone “1601” from the hybridization of Fraxinus mandshurica Rupr. × Fraxinus sogdiana Bunge was showed significant differences in leaf development with its female control “M8”. The leaf phenotypic differences of leaflets and fronds, photosynthesis parameters, rate of leaf water loss and leaf cell size were investigated between 1601 and M8. The leaf phenotypic details showed that the leaflets of 1601 were significantly smaller (leaflet size was 53.78% that of M8) and rounder (leaflet aspect ratio was 66.97% that of M8). Its leaflet margins were more serrated (the serrate number was 33.74% that of M8). The fronds of 1601 had more leaflets (1.17-fold that of M8) and shorter leaflet distance (73.44% that of M8). The photosynthetic heterosis was also significant (the net photosynthetic rate in 1601 was 1.43 times that of M8) and the rate of leaf water loss in 1601 was lower than M8. Meanwhile, the results of the leaf microstructure showed that the mesophyll cell area of M8 was smaller than 1601, indicating that the difference in leaf size was caused by the number of cells. To analyze the reasons for these differences in leaf phenotype and explore the important regulatory genes potentially involved in leaf development, the comparative transcriptome analysis of M8 and 1601 and weighted gene coexpression network analysis (WGCNA) were completed. The results showed that hormones, such as auxins and brassinolides (BRs), along with the transcription factors (TFs), such as the growth-regulating factors (GRFs) and TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATION CELL FACTOR (TCPs), play essential roles in the difference of leaf size between 1601 and M8 by regulating cell proliferation. These data further shed light on the developmental mechanisms of the leaves of F. mandshurica. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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17 pages, 3897 KiB

Open AccessArticle

Differences in the Growth of Seedlings and the Selection of Fast-Growing Species in the Gleditsia Genus

by Feng Xiao, Yang Zhao, Xiurong Wang and Xueyan Jian

Forests 2023, 14(7), 1464; https://doi.org/10.3390/f14071464 - 17 Jul 2023

Cited by 5 | Viewed by 824

Abstract

The Gleditsia genus has various uses, including those for medicinal, edible, chemical, timber, and ornamental purposes, and the genus is widely distributed in China. However, there is still a lack of understanding about the phenotypic and growth differences seen among species within the [...] Read more.

The Gleditsia genus has various uses, including those for medicinal, edible, chemical, timber, and ornamental purposes, and the genus is widely distributed in China. However, there is still a lack of understanding about the phenotypic and growth differences seen among species within the Gleditsia genus. In this study, we compared and analyzed the various species of Gleditsia seedlings in terms of their genotypes, chromosome numbers, physiological growth, photosynthesis, hormone content, and gene expression. The results showed that the genome size of the Gleditsia genus ranges from 686.08 M to 1034.24 M and that all Gleditsia species are diploid. Among the species studied, G. fera can be divided into fast-growing genotype, exhibited several advantages in terms of leaf type and photosynthetic capacity, high levels of GA₃, and fast stem growth, making it a species with the potential for promotion and application. G. delavayi exhibited high levels of auxin and cytokinin and strong photosynthetic capacity, with rapid growth in terms of plant height. G. microphylla had the lowest levels of IAA, IBA, and NAA in the apical, and showed slow growth in terms of plant height. Weighted correlation network analysis (WGCNA) identified the hub genes associated with traits. This study lays a material and theoretical foundation for the development of new resources for Gleditsia breeding and rootstock selection and provides a basis for the mechanism of rootstock–scion interaction. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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12 pages, 4277 KiB

Open AccessArticle

Study on the Rooting Physiological Mechanism of Schisandra chinensis (Turcz.) Baill. Green-Branched Cuttings

by Dan Sun, Xilin Zhao, Jun Ai, Zhenxing Wang, Guangli Shi, Yumeng Liu, Xiang Li and Chengcheng Zhao

Forests 2023, 14(7), 1365; https://doi.org/10.3390/f14071365 - 03 Jul 2023

Viewed by 920

Abstract

Schisandra chinensis (Turcz.) Baill. is an important medicinal plant in northeast China. Cutting propagation is an effective method for the rapid propagation of many tree species. This research aimed to determine a suitable growing medium and appropriate root hormone type, concentration and treatment [...] Read more.

Schisandra chinensis (Turcz.) Baill. is an important medicinal plant in northeast China. Cutting propagation is an effective method for the rapid propagation of many tree species. This research aimed to determine a suitable growing medium and appropriate root hormone type, concentration and treatment time through the utilization of different substrates and hormones to treat one-year-old branches of S. chinensis. The optimal treatment achieved a rooting rate of 60% with 225 ppm ABT and 75 ppm NAA for 2.5 h. The substrate of vermiculite/perlite = 1:1 (urea+potassium) was beneficial to the adventitious root formation, which reached 79%. The adventitious root primordium of S. chinensis originated from the junction of the xylem and cambium. ABT and NAA treatments altered the peak timing of POD, PPO and IAAO in S. chinensis cuttings. During the adventitious root formation of S. chinensis cuttings, the high endogenous IAA concentration promoted the occurrence of adventitious roots in the early stage and the lower endogenous IAA and GA₃ concentrations promoted the elongation and growth of adventitious roots in the later period. Low ABA and ZR concentrations enabled adventitious root formation and elongation. An efficient cutting propagation system would enable the mass propagation of S. chinensis seedlings. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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12 pages, 2545 KiB

Open AccessArticle

Establishment of a Highly Efficient In Vitro Regeneration System for Rhododendron aureum

by Wenna Zhao, Hao Dong, Hui Hou, Yajing Ning, Liqiang Mu and Shujuan Li

Forests 2023, 14(7), 1335; https://doi.org/10.3390/f14071335 - 29 Jun 2023

Viewed by 865

Abstract

Rhododendron aureum is identified as a vulnerable species in China. The establishment of an in vitro regeneration system assists significantly in species protection. Here, an in vitro regeneration system was developed using both direct and indirect organogenesis pathways. The role of thidiazuron (TDZ) [...] Read more.

Rhododendron aureum is identified as a vulnerable species in China. The establishment of an in vitro regeneration system assists significantly in species protection. Here, an in vitro regeneration system was developed using both direct and indirect organogenesis pathways. The role of thidiazuron (TDZ) in different developmental stages was also investigated. The leaves of wild-harvested R. aureum plants were used for callus induction after hydroponic cultivation. The optimal formula was found to be woody plant basal medium (WPM) supplemented with 0.5 mg·L⁻¹ TDZ and 0.5 mg·L⁻¹ 3-indolebutyric acid (IBA), while the optimal formula for the subculture and induction of adventitious buds was WPM containing 0.1 mg·L⁻¹ TDZ and 0.5 mg·L⁻¹ IBA. The leaves from tissue-cultured seedlings were then used for the induction of bud clusters. An association was observed between the differentiation of bud clusters and the ratio of auxin and cytokinin. The optimal formula for the induction of bud clusters was WPM containing 0.5 mg·L⁻¹ TDZ and 0.1 mg·L⁻¹ IBA, yielding a 50% induction rate and the maximum number of buds. Higher concentrations of TDZ were found to be beneficial for bud proliferation, while a lower concentration was conducive to stem elongation. The optimal formula for subculture was WPM containing 0.1 mg·L⁻¹ TDZ and 0.5 mg·L⁻¹ IBA, while that for stem elongation was WPM supplemented with 0.002 mg·L⁻¹ TDZ and 0.5 mg·L⁻¹ IBA. Only IBA was found to be necessary for rooting, with increased IBA concentrations leading to an increased number of roots and earlier root formation, with larger callus areas; thus, an IBA concentration of 1.0 mg·L⁻¹ was found to be optimal for the rooting of R. aureum. After hardening the seedlings for two days, a substrate composed of vermiculite and peat soil in a 10:1 ratio was identified as a transplantation formula. This system provides directions both for the protection of endangered species and the promotion of industrial development. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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15 pages, 2697 KiB

Open AccessArticle

Physiological and Gene Expression Response of Interspecific Hybrids of Fraxinus mandshurica × Fraxinus americana to MJ or SNP under Drought

by Yang Cao, Liming He, Fei Song, Chuanzhou Li, Qitian Ji, Jianfei Liu, Guangzhou Peng, Boyao Li, Fansuo Zeng and Yaguang Zhan

Forests 2023, 14(6), 1277; https://doi.org/10.3390/f14061277 - 20 Jun 2023

Viewed by 915

Abstract

Drought affects the growth and production of Fraxinus tree species, such as the precious woody plant Fraxinus mandshurica. Based on interspecific hybrid F1 combinations, D110 plants of F. mandshurica × F. americana with strong drought resistance were selected for this study. To further [...] Read more.

Drought affects the growth and production of Fraxinus tree species, such as the precious woody plant Fraxinus mandshurica. Based on interspecific hybrid F1 combinations, D110 plants of F. mandshurica × F. americana with strong drought resistance were selected for this study. To further reveal their heterosis mechanism under drought, in this study, an analysis was conducted pertaining to the physiological indexes and gene expression of related key gene changes in materials of 5 yr D110 seedlings and their female and male parental controls (D113 and 4–3) in response to drought, as well as to the addition of sodium nitrate (SNP, a donor of nitric oxide) and methyl jasmonate (MJ, a donor of jasmonate) signal molecules after drought. The results showed that under drought stress, hybrid D110 plants performed significantly better than their parents, especially compared to D113, in plant growth (the plant height growth was 29.48% higher), photosynthesis (the net photosynthetic rate was 38.4% higher), peroxidation (the increase in MDA content was 71.77% lower), defense enzyme activity (SOD and POD activities were 36.63% and 65.58% higher), hormone contents (ABA, IAA and GA were 33.9%~51.2% higher) and gene expression (the LHY and TOC1 rhythmic genes were 131.97%~165.81% higher). When an exogenous additive agent (SNP or MJ) was applied after drought, the negative effects of drought on growth were effectively alleviated (the tree height growth of D110 increased from 22.76% to 22.32% in comparison to drought conditions); meanwhile, the height growth of D110 plants was significantly higher than that of their parents. Further results of physiological indexes and the expression of related key gene changes in response to SNP or MJ also indicated that D110 plants can recover faster from drought than their parents after application of SNP or MJ. This article provides new ideas for revealing the heterosis mechanism of the drought resistance of interspecific F1 hybrids and supplies effective measures for improving drought resistance in F. mandshurica. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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18 pages, 4513 KiB

Open AccessArticle

Spermosphere Bacteria Promote Ormosia henryi Seed Germination by Activating Metabolic Pathways

by Meng Ge and Xiaoli Wei

Forests 2023, 14(6), 1136; https://doi.org/10.3390/f14061136 - 31 May 2023

Cited by 2 | Viewed by 1345

Abstract

Spermosphere microorganisms are affected by seed exudates (carbon deposits) and interact with each other around the germinating seeds. The interactions in this region will have an important impact on seed germination, plant growth, and development. Ormosia henryi Prain is a rare and endangered [...] Read more.

Spermosphere microorganisms are affected by seed exudates (carbon deposits) and interact with each other around the germinating seeds. The interactions in this region will have an important impact on seed germination, plant growth, and development. Ormosia henryi Prain is a rare and endangered tree species with hardseed in China that generally shows low levels of natural regeneration. However, good levels of natural regeneration were observed under a few mother trees in Guanling County (Guizhou Province, China). Based on this phenomenon: we raise the question: Is the seed germination of Ormosia henryi in high-level natural regeneration areas driven by the spermosphere microbe and what is the driving mechanism? The purpose of this study was to explore the promoting role of spermosphere bacteria in different stages of germination, so as to provide a theoretical basis for screening strong colonization ability spermosphere functional bacteria. Thus, in this study, we designed a germination experiment simulating the natural soil (sterilized and unsterilized) of Guanling County. We used 16S rRNA gene sequencing and widely targeted multiple reaction monitoring (MRM) metabolomic analysis to analyze bacterial microbial diversity and the metabolic profiles of seed exudates at the four stages of seed germination: imbibition, radicle protrusion, radicle elongation, and cotyledon protrusion. The results indicated that some spermosphere bacteria: taxa of Bacillus, Acidobacteriales, Nitrospira, and Ellin6067, and other functional bacteria may play important roles in promoting seed germination depending largely on their functional characteristics and abundance. The critical period for spermosphere bacteria to promote seed germination was at the radicle protrusion stage in the unsterilized soil group, levels of metabolites such as sugars and amino acids of seed exudates were increased in this stage, more respiratory pathways were activated and seed respiratory metabolism was enhanced. Spermosphere bacteria of wild Ormosia henryi in the Guanling area appeared to promote the germination of O. henryi seeds, mainly through activating galactose metabolism and the lysine degradation pathway to provide energy for germination. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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14 pages, 4759 KiB

Open AccessArticle

Development of the Vascular Cambium of Taxodium ascendens and Its Seasonal Activities in Subtropical China

by Youming Xu, Cong Liu, Han Lin, Kunxi Wang and Zhuang Han

Forests 2023, 14(6), 1071; https://doi.org/10.3390/f14061071 - 23 May 2023

Viewed by 1167

Abstract

The vascular cambium is an extensive and permanent secondary meristem with wood cells products of periclinal divisions commonly contributed to two directions and arranged in radial files of trees. Cambium activity is the origin of timber production. Taxodium ascendens Brongn is an exotic [...] Read more.

The vascular cambium is an extensive and permanent secondary meristem with wood cells products of periclinal divisions commonly contributed to two directions and arranged in radial files of trees. Cambium activity is the origin of timber production. Taxodium ascendens Brongn is an exotic species in China, and its apical meristem and cambial activity are still elusive, resulting in a lack of understanding about its wood formation and improvement. We thus addressed this knowledge gap by studying Cambium activity. For studying, twigs from five 30-year-old healthy trees were collected between February-2017 and March-2018. Anatomy deciphered its apical meristem with a Cryptomeria–Abies type. The procambium appeared after leaf primordium and initially presented five lobes as observed transversely from a one-year-old shoot. The procambium under the apical differentiated into protophloem first and then protoxylem toward the inside. It means that protoxylem differentiated later than protophloem did. After dormancy, the vascular cambium began to be active, starting in early April 2017, which was later than shoot differentiation. On 25 July 2017, the cambial zone had 9–10 immature xylem cell layers. Both initiation and cessation of the xylem preceded that of the phloem. Until 10 October 2017, few immature elements were found, indicating the translation of cells from activity to dormancy. On 15 November 2017, the cambium contained 3–4 cells in radial rows, which demonstrated the dormancy of the cambium until next spring. Furthermore, immature xylem elements increased as cell layers in the cambium zone and cell fission increased. The growth pattern of T. ascendens revealed that cambial activity is highly seasonal and dependent on changes in abiotic conditions. Thus, the wood formation in the species will be significantly altered in a changing climatic pattern. These enhance our understanding of tree growth science, wood formation, wood structure, wood properties variation and wood improvement in tree breeding. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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13 pages, 2669 KiB

Open AccessArticle

A Stable and Efficient Genetic Transformation Method for Embryogenic Callus of Fraxinus mandshurica

by Yan An, Hao Dong, Wenna Zhao, Hailong Shen, Ling Yang and Shujuan Li

Forests 2023, 14(5), 957; https://doi.org/10.3390/f14050957 - 06 May 2023

Viewed by 1209

Abstract

Fraxinus mandshurica is a widely used greening and ornamental tree species. However, its genetic transformation system has been hampered by problems such as low transformation efficiency, among others, which can hinder research related to molecular breeding and the analysis of functional genes. Thus, [...] Read more.

Fraxinus mandshurica is a widely used greening and ornamental tree species. However, its genetic transformation system has been hampered by problems such as low transformation efficiency, among others, which can hinder research related to molecular breeding and the analysis of functional genes. Thus, in this study, a novel genetic transformation method for efficient transformation of the embryonic callus of Fraxinus mandshurica was investigated. The method was optimized in terms of factors such as antibiotics, infection solution concentrations, co-culture time, and somatic embryo maturation. The results indicated that the optimal antibiotic concentration was 10 mg·L⁻¹ of hygromycin (Hyg). At this point, the callus proliferation multiple was only 0.12. The highest transformation efficiency was found to be 93.93% when the absorbance of the infection solution concentration at OD₆₀₀ was 0.4. Interestingly, transformation efficiency was found to be highest (77.9%) at 48 h of co-culture, with a GUS staining rate of 88.23%. The medium for somatic embryo maturation of transformed callus was half-strength MS medium (MS 1/2) containing 60 g·L⁻¹ polyethylene glycol, 1 mg·L⁻¹ abscisic acid, 400 mg·L⁻¹ casein enzymatic hydrolysate (CH), 20 g·L⁻¹ sucrose, 1 g·L⁻¹ activated charcoal, and 5 g·L⁻¹ gellan gum. The medium for somatic embryo germination was MS ½, containing 0.2 mg·L⁻¹ of N-(Phenylmethyl)-9H-purin-6-amine(6-BA) and 5.0 mg·L⁻¹ of gibberellin (GA). These results are of significance for the verification of the gene function and future genetic improvement of Fraxinus mandshurica. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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14 pages, 2341 KiB

Open AccessArticle

Optimization of Key Technologies for Induction of Embryogenic Callus and Maturation of Somatic Embryos in Korean Pine (Pinus koraiensis)

by Fang Gao, Yujie Shi, Ruirui Wang, Iraida Nikolaevna Tretyakova, Alexander Mikhaylovich Nosov, Hailong Shen and Ling Yang

Forests 2023, 14(4), 850; https://doi.org/10.3390/f14040850 - 20 Apr 2023

Viewed by 1306

Abstract

Somatic embryogenesis (SE), which leads to the formation of embryonic callus (EC) tissue, is the most promising method for large-scale production and selective breeding of woody plants. However, in many species, SE suffers from low induction and proliferation rates, hindering the production of [...] Read more.

Somatic embryogenesis (SE), which leads to the formation of embryonic callus (EC) tissue, is the most promising method for large-scale production and selective breeding of woody plants. However, in many species, SE suffers from low induction and proliferation rates, hindering the production of improved plant materials. We investigated the effects of the explant sterilization method, 4 °C cryopreservation, basal medium, ethylene removal, liquid medium supplementation, and a combination of PGRs on embryogenic callus (EC) induction of Korean pine, using immature embryos of Korean pine as explants. The effects of sucrose and maltose on EC proliferation and maturation were investigated. The differences in the maturation ability of EC somatic embryos before and after cryopreservation were evaluated using the induced embryonic cell lines. The results showed that zygotic embryos (ZEs) performed better than megagametophytes (MGs) as explants. The induction rate of EC was significantly increased after 28 days of cryopreservation at 4 °C. The induction rate of EC in the #5 family increased from 10.00% to 62.8%. The EC induction rate of the five families cultured with the DCR basal medium was higher than that with the mLV basal medium. Among them, the induction rate of the #5 family cultured with the mLV basal medium was 23.3%, while that with the DCR basal medium was 60.9%, an increase of 2.6 times. There was no significant difference in the maturation ability of EC somatic embryos before and after cryopreservation. In conclusion, this study provides a method to improve the EC induction rate and maturation ability of Korean pine. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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12 pages, 3767 KiB

Open AccessArticle

Weighted Gene Co-Expression Network Analysis Reveals Key Pathways and Hub Genes Associated with Successful Grafting in Pecan (Carya illinoinensis)

by Zhenghai Mo, Xiaozhuang Jiang, Yan Zhang, Min Zhai, Longjiao Hu and Jiping Xuan

Forests 2023, 14(4), 835; https://doi.org/10.3390/f14040835 - 19 Apr 2023

Cited by 2 | Viewed by 1118

Abstract

Patch budding (bud grafting) is a commonly used method for pecan reproduction; however, the grafting survival rate varies with cultivars. Clarifying the underlying mechanisms of successful grafting is pivotal for graft technique improvement. Here, weighted gene co-expression network analysis (WGCNA) was conducted to [...] Read more.

Patch budding (bud grafting) is a commonly used method for pecan reproduction; however, the grafting survival rate varies with cultivars. Clarifying the underlying mechanisms of successful grafting is pivotal for graft technique improvement. Here, weighted gene co-expression network analysis (WGCNA) was conducted to dissect the key pathways and genes related to the successful grafting of pecan. Based on the transcriptome data of two contrasting cultivars (an easy-to-survive cultivar ‘Pawnee’ and a difficult-to-survive cultivar ‘Jinhua’) in response to budding, all the genes with variable transcripts were grouped into 18 modules. There were two modules that were significantly correlated with the trait of different cultivars. Enrichment analysis showed that several enriched gene ontology (GO) terms were related to oxidative detoxification and genes associated with hormone signaling pathway occupied a high ratio for the two modules. A total of 52 hub genes were identified, and 48 showed promoter polymorphisms between the two cultivars. Our study suggested that oxidative detoxification and hormone signaling were probably the key pathways for the successful grafting of pecan. The 48 hub genes identified here might be the key genes that led to the divergence of graft survival rates among different pecan cultivars. Our results will lay a foundation for future graft technique improvement in pecan. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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19 pages, 5760 KiB

Open AccessArticle

Genome-Wide Identification and Expression Analysis of the TCP Genes in Jatropha curcas L. Reveals Its Roles in Involvement of Leaf Shape

by Rong Zou, Yang Peng, Yang Zhao and Xiurong Wang

Forests 2023, 14(4), 780; https://doi.org/10.3390/f14040780 - 10 Apr 2023

Cited by 1 | Viewed by 1222

Abstract

Jatropha curcas var. nigroviensrugosus CV Yang (Jn) exhibits wrinkled leaves and higher flowering and fruiting rates compared to Jatropha curcas L. (Jc). Teosinte branched1/Cincinnata/Proliferating cell factors (TCPs) are known to play crucial roles in plant development and [...] Read more.

Jatropha curcas var. nigroviensrugosus CV Yang (Jn) exhibits wrinkled leaves and higher flowering and fruiting rates compared to Jatropha curcas L. (Jc). Teosinte branched1/Cincinnata/Proliferating cell factors (TCPs) are known to play crucial roles in plant development and physiological processes. However, it remains unknown whether or not the TCP gene family regulates in leaf development of Jc and Jn. Here, we systematically performed a genome-wide analysis of the Jc TCP family and investigated the differences in the expression of TCP in different leaf morphologies. In total, our results showed that 18 TCP members were identified in the whole genome sequence of Jatropha curcas L.; Jc TCP genes were classified into two categories by phylogenetic tree construction, among which there were 11 members in the Class I subfamily, seven members in the Class Ⅱ subfamily. It was shown that 12 members of Jc TCP genes were located at the seven chromosomes, and proteins belonging to the same TCP group exhibit higher similarity than those from different groups. Furthermore, the expression profiles of 15 TCP genes were discovered at different leaf developmental stages of Jc and Jn. Jc TCP 4, Jc TCP 5, Jc TCP 8, Jc TCP 13, Jc TCP 14, and Jc TCP 16 showed significantly different expressions, and can be used as candidate genes for regulating leaf development. Therefore, the TCP genes play important roles in regulating the leaf development in Jc, and the manipulation of Jc TCP genes can potentially be an important tool used for the genetic improvement of the leaf. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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21 pages, 2233 KiB

Open AccessArticle

Comprehensive Evaluation of Quality Traits of Hovenia acerba Germplasm Resources in Fujian Province

by Zhijian Yang, Hui Chen, Chaimei Lin, Jindian Sun, Wenling Wen, Xiangjin Zhu, Yousry A. El-Kassaby and Jinling Feng

Forests 2023, 14(2), 204; https://doi.org/10.3390/f14020204 - 20 Jan 2023

Cited by 1 | Viewed by 1324

Abstract

Hovenia acerba is a precious medicinal and edible tree. We assessed the genetic variation of H. acerba quality traits and conducted a comprehensive germplasm resource evaluation to provide a theoretical basis for breeding edible, medicinal, and edible/medicine combination varieties. We evaluated 31 H. [...] Read more.

Hovenia acerba is a precious medicinal and edible tree. We assessed the genetic variation of H. acerba quality traits and conducted a comprehensive germplasm resource evaluation to provide a theoretical basis for breeding edible, medicinal, and edible/medicine combination varieties. We evaluated 31 H. acerba germplasm resources, including 12 infructescence and 8 fruit quality traits using correlation, principal component, and cluster analyses. The results showed that there were significant differences in all quality traits, with an average coefficient of variation greater than 0.20, an average genetic diversity greater than 1.80, and an average repeatability greater than 0.90. The average genetic variation and repeatability of quality traits in infructescence were higher than fruit. Infructescence K, Ca, Mn, Mg, and reducing sugar contents are important indicators in evaluating infructescence and fruit quality traits, and infructescence K, Mg, and reducing sugar contents are also quality innovation indices of H. acerba germplasms. Tannin, protein, and soluble sugar were the most suitable quality components for screening, followed by reducing sugar, starch, fat, total saponins, and total flavones. According to principal component factor scores and cluster analysis results, specific genotypes were selected as breeding materials for infructescence protein, tannin, flavone, reductive sugar, fruit tannin, fat, flavonoid, saponin, protein, and starch. The correlation analysis with environmental factors showed that the total amount of applied water could influence H. acerba infructescence and fruit quality. In conclusion, the variability of H. acerba germplasm resources was rich, and selection potential is large, which is beneficial to germplasm quality innovation and breeding. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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Review

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21 pages, 1444 KiB

Open AccessReview

Developments on Core Collections of Plant Genetic Resources: Do We Know Enough?

by Rui Gu, Shaohui Fan, Songpo Wei, Jiarui Li, Shihui Zheng and Guanglu Liu

Forests 2023, 14(5), 926; https://doi.org/10.3390/f14050926 - 29 Apr 2023

Cited by 4 | Viewed by 2833

Abstract

The core collection is a small subset that minimizes genetic redundancy while preserving the maximum genetic diversity of the entire population. Research on the core collection is crucial for the efficient management and utilization of germplasm resources. In this paper, the concept of [...] Read more.

The core collection is a small subset that minimizes genetic redundancy while preserving the maximum genetic diversity of the entire population. Research on the core collection is crucial for the efficient management and utilization of germplasm resources. In this paper, the concept of the core collection and the research progress of its construction have briefly been summarized. Subsequently, some perspectives have been proposed in this research field for the near future. Four novel opinions have been presented, (1) the effective integration of multiple data types and accurate phenotyping methods need to be focused on; (2) the sampling strategy and bioinformatics software should be given attention; (3) the core collection of afforestation tree and bamboo species, with a wide natural distribution range and a large planting area, need to be carried out as soon as possible; (4) we should place a high priority on the study of genes discoveries and utilize these with a rapid, precise and high-throughput pattern based on re-sequencing technology. This paper provides a theoretical and technological reference for further study and the application of the plant core collection. Full article

(This article belongs to the Special Issue Advances in Tree Germplasm Innovation and High-Efficiency Propagation)

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