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ASHS 2024 Annual Conference

 

Ning Qing 1: A New Holly Cultivar With Broadly Ovate Leaf Morphology

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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Yanwei 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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Chuanyong Wang 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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Yunlong Li 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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Ilex L. (holly), Aquifoliaceae, represents the largest woody dioecious genus within the angiosperm phylum. Ilex species are primarily cultivated for their ornamental and pharmaceutical properties (Yao et al. 2022; Zhou et al. 2022). There are ∼700 deciduous and evergreen trees or shrubs in the Ilex genus, distributed globally from tropical to temperate regions. China, in particular, nourishes more than 200 documented species (Cuénoud et al. 2000; Su et al. 2020; Yao et al. 2020). Although hundreds of species exist in the genus Ilex, their flowers and fruits are fairly uniform compared with their leaves (Yao et al. 2016). Ilex leaves are diverse in terms of texture, shape, size, color, and margins, and these characteristics significantly contribute to their germplasm identification and commercial values (Chong et al. 2022). Ilex dabieshanensis ‘Ning Qing 3’ is a unique cultivar for its peculiar oblong leaf morphology (Chong et al. 2023).

The most prominent “industry standard” hollies currently in the market are Ilex verticillata (deciduous) and Ilex ×attenuata ‘Sunny Foster’ (evergreen). I. verticillata is popular for its bright red fruits, whereas I. attenuata ‘Sunny Foster’ is characterized by the golden narrow leaves. ‘Ning Qing 1’ was developed and introduced by the Institute of Botany, Jiangsu Province, and the Chinese Academy of Sciences (Nanjing Botanical Garden Memorial Sun Yat-Sen). The evergreen cultivar exhibits arbor-like growth and features leathery, broadly ovate, shiny dark green (RHS NN137B) (Royal Horticultural Society 2015) leaves, along with an abundance of red fruits. ‘Ning Qing 1’ enriches the genetic resources of Ilex and substantially enhances its ornamental value.

Origin

In Spring 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 Spring 2015, these seeds were sown in a seedbed with a substrate mixture of perlite and peat. After germination, seedlings were transferred into the field with a spacing of 30 × 30 cm. In May 2017, an individual plant with leathery, broadly ovate, shiny, and dark green (RHS NN137B) (Royal Horticultural Society 2015) leaves was identified and selected for further evaluation, eventually named ‘Ning Qing 1’. After 4 years of softwood/hardwood cutting regeneration (2018–21) and 6 years of field observation (2018–23), the liners (rooted stem cuttings) exhibited the same morphological characteristics as the mother plant, confirming their phenotypic stability (Table 1). The cultivar displayed vigorous growth in Jiangsu (32°03′N, 118°49′E, about US Department of Agriculture plant hardiness zones 9b/10a), tolerating high (37 to 40 °C) and low (−5 to 0 °C) temperatures with only a few incidents of leaf spots. The Forest Variety Certification Committee of China authorized the cultivar in 2023.

Table 1.

Field observations of major phenotypic traits of Ilex ‘Ning Qing 1’ (left) and its cuttings (right).

Table 1.

Description

Among existing Ilex germplasm, ‘Ning Qing 1’ shares similarities with Ilex integra ‘Happy Princess’, released by Ningbo Academy of Agricultural Sciences in 2020. Although ‘Happy Princess’ has an umbellate inflorescence, ‘Ning Qing 1’ features a cymose inflorescence. These two cultivars also differ in their leaf (base) shapes: Happy Princess has elliptic (cuneiform) bases, and Ning Qing 1 has broadly ovate (circular) bases (Table 2, Fig. 1). Specific characteristics of ‘Ning Qing 1’ include the following.

Table 2.

Comparison of leaf and flower morphology between Ilex ‘Happy Princess’ and Ilex ‘Ning Qing 1’.

Table 2.
Fig. 1.
Fig. 1.

Comparison of floral and leaf attributes among Ilex ‘Happy Princess’ (A) and Ilex ‘Ning Qing 1’ (B). Photographs were taken at the Ningbo Academy of Agricultural Sciences in Apr 2020 (A), and at the Nanjing Botanical Garden in Apr 2023 and Dec 2022 (B and C).

Citation: HortScience 58, 12; 10.21273/HORTSCI17413-23

Habit.

It is an evergreen tree with upright growth and an open canopy, reaching up to 2.0 m in height and spreading to 1.5 m at 6 years of age (Fig. 2A).

Fig. 2.
Fig. 2.

Phenotypic characteristics of Ilex ‘Ning Qiang 1’ (AC). (A) Upright growth habit with an open canopy. (B) Axillary cymose inflorescence and greenish yellow flowers; shiny, leathery, dark green (RHS NN137B), and broadly ovate leaves. (C) Green subglobose fruits with discoid stigmas that will turn red (RHS 45A) when they have matured. Photographs AC were taken at the Nanjing Botanical Garden in Jan, Apr, and Aug 2023.

Citation: HortScience 58, 12; 10.21273/HORTSCI17413-23

Branches and foliage.

The branches are sturdy (3.5–5.0 mm in diameter) and yellowish green (RHS 144B) without lenticels. Mature leaves are leathery and dark green (RHS NN137B), transitioning from thin, leathery, yellowish green (RHS 144A) when young. Leaf blades are broadly ovate (8–9 cm in length × 5–6 cm in width) with short petioles (0.8–1.0 cm). Leaf bases are circular, and the apexes are acuminate. Deep veins are embedded in leaf surfaces, and the mesophyll tissues are raised (Fig. 2B).

Flower.

Each cymose inflorescence features eight to 15 small, greenish-yellow, axillary flowers, inconspicuously grown on the current year’s branchlets. Each flower has four obovate-oblong petals that are (4.0–4.1 mm in length × 2.2–2.5 mm in width), slightly connate at the base. Four degenerated stamens and a large pistil are inside the petals (Fig. 2B). In Jiangsu Province, the plant starts to bloom in late April, and the flowering period can last ∼2 weeks.

Fruit.

Abundant fruits ripen in October and can persist through the winter until the next January. When mature, the subglobose fruits (6–9 mm in diameter) turn red (RHS 45A) with discoid stigmas still present (Fig. 2C).

Propagation

‘Ning Qing 1’ is primarily regenerated through semihardwood stem cutting (June to July in Jiangsu) or hardwood stem cutting (late November to late March before sprouting). For semihardwood stem cutting, select the current year’s semilignified branches and cut them into short cuttings (∼6 to 10 cm long) with two to three leaves trimmed half-way at the top. For hardwood stem cutting, choose thick and healthy branches from the current year, cutting them into 10- to 15-cm lengths, with an approximate cutting depth of 4 to 6 cm. To improve the rooting percentage, treat the cuttings with 2000 ppm indole-3-butyric acid for 8 to 10 s. Then, insert them into the substrate (Vpeatmoss:Vperlite ≈ 1:1), maintain moderate humidity, and use sprinkler irrigation. Generally, the stem cuttings will root after 30 d, with a rooting percentage reaching up to 90% (average percentage of 82% for semihardwood stem cutting and 71% for hardwood stem cutting).

Cultivation

This cultivar grows well in full sun and tolerates partial shade conditions. It is recommended to plant the cultivar in acidic soil. Transplantation with slight soil is suggested in early spring, followed by thorough irrigation. Little pruning and reshaping of plants is necessary as required. Timely drainage during the rainy season and fertilizer applications in winter and spring also play crucial roles in plant growth. Pests or diseases have not posed significant concern, with only a few incidents of leaf spots observed.

Availability

The plant ‘Ning Qing 1’ 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.

    • 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
  • Fig. 1.

    Comparison of floral and leaf attributes among Ilex ‘Happy Princess’ (A) and Ilex ‘Ning Qing 1’ (B). Photographs were taken at the Ningbo Academy of Agricultural Sciences in Apr 2020 (A), and at the Nanjing Botanical Garden in Apr 2023 and Dec 2022 (B and C).

  • Fig. 2.

    Phenotypic characteristics of Ilex ‘Ning Qiang 1’ (AC). (A) Upright growth habit with an open canopy. (B) Axillary cymose inflorescence and greenish yellow flowers; shiny, leathery, dark green (RHS NN137B), and broadly ovate leaves. (C) Green subglobose fruits with discoid stigmas that will turn red (RHS 45A) when they have matured. Photographs AC were taken at the Nanjing Botanical Garden in Jan, Apr, and Aug 2023.

  • 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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Yanwei 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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Chuanyong Wang 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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Yunlong Li 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 supported by the National Natural Science Foundation of China (32201618), the Natural Science Foundation of Jiangsu Province (BK20220751), and the Opening Project of Zhejiang Provincial Key Laboratory of Forest Aromatic Plants-based Healthcare Functions (SLFX202205).

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

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