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ASHS 2024 Annual Conference

 

Ning Qing 4: A New Holly Cultivar with Elliptic and Serrated Leaves

Authors:
Ting Zhou Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Xinran Chong Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Fan Zhang Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Xiaoqing Lu Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Donglin Zhang Department of Horticulture, University of Georgia, Athens, GA 30602, USA

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Hong Chen Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China; and Zhejiang Provincial Key Laboratory of Forest Aromatic Plants-based Healthcare Functions, Zhejiang A & F University, Hangzhou 311300, China

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The genus Ilex L. (Aquifoliaceae) stands as the largest genus of woody dioecious plants in angiosperm, boasting a worldwide distribution of more than 700 species and ranging from tropical to temperate regions (Yao et al. 2022; Zhou et al. 2022). These species encompass both evergreen and deciduous trees or shrubs and are primarily cultivated for their ornamental and pharmaceutical attributes (Cuénoud et al. 2000; Su et al. 2020; Yao et al. 2020). Although the genus Ilex harbors hundreds of species, its flowers and fruits exhibit remarkable uniformity when compared with the diversity found in their leaves (Yao et al. 2016). The leaf phenotypes of Ilex species are remarkably diverse in terms of shape, texture, size, color, and margins, significantly enhancing their commercial values and providing a solid foundation for germplasm identification (Chong et al. 2022). Ilex dabieshanensis ‘Ning Qing 3’ stands out with its unique oblong leaf morphology (Chong et al. 2023). I. dabieshanensis ‘Ning Qing 1’ is distinctive for its leathery leaf texture, broadly ovate leaf shape, and shiny and blackish green (RHS 146A) (Royal Horticultural Society 2015) leaf color.

Ilex dabieshanensis ‘Ning Qing 4’ was introduced by the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Memorial Sun Yat-Sen). This cultivar has garnered considerable attention for its leathery leaf texture, elliptic leaf shape, serrated leaf margins, and dark green leaf color (RHS 147A). Moreover, it features a pyramid-shaped habit that is highly sought after in landscape greening and home gardening. To date, no significant concerns have arisen regarding pests or diseases.

Origin

I. dabieshanensis is a species native to the Dabie Mountains of western Anhui, China. In the spring of 2014, I. dabieshanensis (♀) was crossbred with Ilex latifolia (♂) at the Repository of Ilex spp. Germplasm of Nanjing Botanical Garden Memorial Sun Yat-Sen, Jiangsu, China (32°03′N, 118°49′E). More than 500 cross-pollinated seeds were collected in winter and stored in moisture sand to break seed dormancy. In the spring of 2015, these seeds were sown in a seedbed with a perlite and peat mixture as substrate. After germination, all the seedlings were transplanted into the field with a 30 × 30-cm spacing. In May 2017, an individual plant with leathery, elliptic, serrated, and dark green (RHS 147A, Royal Horticultural Society 2015) leaves was observed and selected for further evaluation, ultimately receiving the name ‘Ning Qing 4’. After 5 years of semihardwood/hardwood stem cutting (2018–22) and 6 years of field observation (2018–23), the plants resulting from clonal propagation exhibited the same morphological characteristics as the mother plant, confirming their phenotypic stability. Notably, they grew vigorously in Jiangsu (32°03′N, 118°49′E, approximately US Department of Agriculture plant hardiness zones 9b/10a) during the process, tolerating high (37 to 40 °C) and low (−5 to 0 °C) temperatures with only a few incidents of leaf spots observed. The Forest Variety Certification Committee of China authorized the cultivar in 2023.

Description

Among existing Ilex germplasm, ‘Ning Qing 4’ most resembles Ilex integra ‘Happy Princess’, which was released by Ningbo Academy of Agricultural Sciences in 2020. The cultivar Happy Princess has elliptic leaves that are sparsely and deeply serrated, whereas Ning Qing 4 leaves exhibit dense and shallow serrations along the margins (Table 1, Fig. 1). Specific characteristics of ‘Ning Qing 4’ are as follows.

Table 1.

Comparison of leaf morphology among Ilex ‘Happy Princess’, Ilex ‘Ning Qing 4’, and Ilex dabieshanensis.

Table 1.
Fig. 1.
Fig. 1.

Comparison of leaf attributes among Ilex ‘Happy Princess’ (A), Ilex ‘Ning Qing 4’ (B), and Ilex dabieshanensis (C).

Citation: HortScience 59, 1; 10.21273/HORTSCI17436-23

Habit.

The plant is evergreen and displays an arbor-like growth with a pyramid-shaped canopy, which can reach up to 2.5 m in height with a 1.3-m spread at 6 years of age (Fig. 2A).

Fig. 2.
Fig. 2.

Phenotypic characteristics of Ilex ‘Ning Qiang 4’ (AC). (A) Upright growth habit with a pyramid-shaped canopy. (B) Axillary umbellate inflorescence and greenish yellow flowers; leathery, elliptic, dark green (RHS 147A) leaves grown with dense and shallow serrations at the edges. (C) Green, elliptic, and small fruits with discoid stigmas that will turn red (RHS 45A) when they are mature.

Citation: HortScience 59, 1; 10.21273/HORTSCI17436-23

Branches and foliage.

The branches are yellowish green (RHS 144B), measure 3.0–4.0 mm in diameter, and lack lenticels. The mature leaves are leathery and dark green (RHS 147A), whereas the younger ones are thin, leathery, and yellowish green (RHS 146B). ‘Ning Qing 4’ leaf blades are elliptic (5.5–6.5 cm in length × 2.5–2.8 cm in width) and attached to short petioles (0.9–1.0 cm). The leaf bases are cuneiform, and the apexes are acuminate. On the leaf surfaces, parallel leaf veins are visible, but not particularly pronounced (Fig. 2B).

Flower.

Each umbellate inflorescence bears six to ten small, greenish yellow, and axillary flowers, discreetly positioned on the current year’s branchlets (Fig. 2B). Each flower has four obovate-oblong petals (3.9–4.0 mm in length × 2.0–2.3 mm in width), slightly connate at the base. Inside the petals, a large pistil is accessible surrounded by four degenerated stamens. In Jiangsu Province, the plant starts to blossom in late April, with a flowering period lasting ∼2 weeks.

Fruit.

The tree sets abundant fruits, which can persist throughout the winter. These fruits are small (6–9 mm in diameter), elliptic, and usually mature in October. When fully mature, the fruits turn red (RHS 45A), and discoid stigmas remain (Fig. 2C).

Propagation

‘Ning Qing 4’ is primarily regenerated by semihardwood stem cutting (June to July in Jiangsu) or hardwood stem cutting (late November to late March before sprouting). For semihardwood stem cutting, the current year’s semilignified branches should be chosen and then cut into short cuttings (∼6 to 10 cm long) with two to three half leaves kept at the top. For hardwood cutting, thick and healthy annual branches should be selected and cut into cuttings of 10 to 15 cm in length. The cutting depth for ‘Ning Qing 4’ could be ∼4 to 6 cm. To improve the survival rate, cuttings can be priorly treated with 2000 ppm indole-3-butyric acid for 8 to 10 s, and then inserted into the substrate, maintaining moderate humidity, and placed under sprinkler irrigation. Generally, more than 90% of cuttings will root after 30 d.

Cultivation

‘Ning Qing 4’ thrives under full sun and can also tolerate semishaded conditions. For optimal cultivation, acidic soil is recommended. During early spring, transplant with soil ball and ensure thorough irrigation. Minimal pruning and reshaping are required due to its natural pyramid-shaped tree habit. During the rainy season in winter and spring, timely drainage and fertilizer applications play important roles in plant growth. To date, only a few incidents of leaf spot were observed and there are no significant concerns regarding pests or diseases.

Availability

The cultivar ‘Ning Qing 4’ is available from Dr. Chen Hong, Institute of Botany, Jiangsu Province and the Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen).

References Cited

  • Chong XR, Li YL, Yan ML, Wang Y, Li MZ, Zhou YW, Chen H, Lu XQ, Zhang F. 2022. Comparative chloroplast genome analysis of 10 Ilex species and the development of species-specific identification markers. Ind Crops Prod. 187:115408. https://doi.org/10.1016/j.indcrop.2022.115408.

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  • Chong XR, Wang Y, Xu XY, Zhang F, Wang CY, Zhou YW, Zhou T, Li YL, Lu XQ, Chen H. 2023. Efficient virus-induced gene silencing in Ilex dabieshanensis using tobacco rattle virus. Forests. 14:488. https://doi.org/10.3390/f14030488.

    • Search Google Scholar
    • Export Citation
  • Cuénoud P, Spichiger R, Andrews S, Manen JF, Martinez MADP, Loizeau PA. 2000. Molecular phylogeny and biogeography of the genus Ilex L. (Aquifoliaceae). Ann Bot. 85:111122. https://doi.org/10.1006/anbo.1999.1003.

    • Search Google Scholar
    • Export Citation
  • Royal Horticultural Society. 2015. Royal Horticultural Society colour chart. 6th ed. Royal Horticultural Society, London, UK.

  • Su T, Zhang MR, Shan ZY, Li XD, Zhou BY, Wu H, Han M. 2020. Comparative survey of morphological variations and plastid genome sequencing reveals phylogenetic divergence between four endemic Ilex species. Forests. 11:964. https://doi.org/10.3390/f11090964.

    • Search Google Scholar
    • Export Citation
  • Yao X, Song Y, Yang JB, Tan YH, Corlett RT. 2020. Phylogeny and biogeography of the hollies (Ilex L., Aquifoliaceae). J Syst Evol. 59:7382. https://doi.org/10.1111/jse.12567.

    • Search Google Scholar
    • Export Citation
  • Yao X, Tan YH, Liu YY, Song Y, Yang JB, Corlett RT. 2016. Chloroplast genome structure in Ilex (Aquifoliaceae). Sci Rep. 6:28559. https://doi.org/10.1038/srep28559.

    • Search Google Scholar
    • Export Citation
  • Yao X, Zhang F, Corlett RT. 2022. Utilization of the hollies (Ilex L. spp.): A review. Forests. 13:94. https://doi.org/10.3390/f13010094.

    • Search Google Scholar
    • Export Citation
  • Zhou T, Ning K, Mo ZH, Zhang F, Zhou YW, Chong XR, Zhang DL, El-Kassaby YA, Bian J, Chen H. 2022. Complete chloroplast genome of Ilex dabieshanensis: Genome structure, comparative analyses with three traditional Ilex tea species, and its phylogenetic relationships within the family Aquifoliaceae. PLoS One. 17:E0268679. https://doi.org/10.1371/journal.pone.0268679.

    • Search Google Scholar
    • Export Citation
  • Fig. 1.

    Comparison of leaf attributes among Ilex ‘Happy Princess’ (A), Ilex ‘Ning Qing 4’ (B), and Ilex dabieshanensis (C).

  • Fig. 2.

    Phenotypic characteristics of Ilex ‘Ning Qiang 4’ (AC). (A) Upright growth habit with a pyramid-shaped canopy. (B) Axillary umbellate inflorescence and greenish yellow flowers; leathery, elliptic, dark green (RHS 147A) leaves grown with dense and shallow serrations at the edges. (C) Green, elliptic, and small fruits with discoid stigmas that will turn red (RHS 45A) when they are mature.

  • Chong XR, Li YL, Yan ML, Wang Y, Li MZ, Zhou YW, Chen H, Lu XQ, Zhang F. 2022. Comparative chloroplast genome analysis of 10 Ilex species and the development of species-specific identification markers. Ind Crops Prod. 187:115408. https://doi.org/10.1016/j.indcrop.2022.115408.

    • Search Google Scholar
    • Export Citation
  • Chong XR, Wang Y, Xu XY, Zhang F, Wang CY, Zhou YW, Zhou T, Li YL, Lu XQ, Chen H. 2023. Efficient virus-induced gene silencing in Ilex dabieshanensis using tobacco rattle virus. Forests. 14:488. https://doi.org/10.3390/f14030488.

    • Search Google Scholar
    • Export Citation
  • Cuénoud P, Spichiger R, Andrews S, Manen JF, Martinez MADP, Loizeau PA. 2000. Molecular phylogeny and biogeography of the genus Ilex L. (Aquifoliaceae). Ann Bot. 85:111122. https://doi.org/10.1006/anbo.1999.1003.

    • Search Google Scholar
    • Export Citation
  • Royal Horticultural Society. 2015. Royal Horticultural Society colour chart. 6th ed. Royal Horticultural Society, London, UK.

  • Su T, Zhang MR, Shan ZY, Li XD, Zhou BY, Wu H, Han M. 2020. Comparative survey of morphological variations and plastid genome sequencing reveals phylogenetic divergence between four endemic Ilex species. Forests. 11:964. https://doi.org/10.3390/f11090964.

    • Search Google Scholar
    • Export Citation
  • Yao X, Song Y, Yang JB, Tan YH, Corlett RT. 2020. Phylogeny and biogeography of the hollies (Ilex L., Aquifoliaceae). J Syst Evol. 59:7382. https://doi.org/10.1111/jse.12567.

    • Search Google Scholar
    • Export Citation
  • Yao X, Tan YH, Liu YY, Song Y, Yang JB, Corlett RT. 2016. Chloroplast genome structure in Ilex (Aquifoliaceae). Sci Rep. 6:28559. https://doi.org/10.1038/srep28559.

    • Search Google Scholar
    • Export Citation
  • Yao X, Zhang F, Corlett RT. 2022. Utilization of the hollies (Ilex L. spp.): A review. Forests. 13:94. https://doi.org/10.3390/f13010094.

    • Search Google Scholar
    • Export Citation
  • Zhou T, Ning K, Mo ZH, Zhang F, Zhou YW, Chong XR, Zhang DL, El-Kassaby YA, Bian J, Chen H. 2022. Complete chloroplast genome of Ilex dabieshanensis: Genome structure, comparative analyses with three traditional Ilex tea species, and its phylogenetic relationships within the family Aquifoliaceae. PLoS One. 17:E0268679. https://doi.org/10.1371/journal.pone.0268679.

    • Search Google Scholar
    • Export Citation
Ting Zhou Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Xinran Chong Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Fan Zhang Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Xiaoqing Lu Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China

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Donglin Zhang Department of Horticulture, University of Georgia, Athens, GA 30602, USA

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Hong Chen Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen), Nanjing 210014, China; and Zhejiang Provincial Key Laboratory of Forest Aromatic Plants-based Healthcare Functions, Zhejiang A & F University, Hangzhou 311300, China

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Contributor Notes

This study was funded by the National Natural Science Foundation of China (32201618), the Opening Project of Zhejiang Provincial Key Laboratory of Forest Aromatic Plants-based Healthcare Functions (SLFX202205), and the Natural Science Foundation of Jiangsu Province (BK20220751).

H.C. is the corresponding author. E-mail: chenhong@cnbg.net.

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