‘Ning Qing 2’: A New Dwarf Holly Cultivar with Small Serrated Leaves

Authors:
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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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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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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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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Xiaolong Cai 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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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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Among angiosperms, the Ilex L. (holly), Aquifoliaceae, is the largest woody dioecious genus, encompassing ∼700 evergreen and deciduous trees or shrubs (Yao et al. 2022; Zhou et al. 2022). Distribution is worldwide from tropical to temperate regions, including China, where more than 200 species have been documented, and they are cultivated mainly as ornamental and pharmaceutical plants (Cuénoud et al. 2000; Su et al. 2020; Yao et al. 2020). Although hundreds of species exist in the genus Ilex, the flowers and fruit are considerably uniform when compared with their leaf morphology (Yao et al. 2016). Leaf morphology plays an important role in Ilex germplasm identification and subtly determining their commercial values based on the large diversity in texture, size, shape, color, and even margins (Chong et al. 2022). For example, Ilex dabieshanensis is characterized by its broad, elliptical, and bright-green [Royal Horticultural Society (RHS) NN137A] (Royal Horticultural Society 2015) leaves. Ilex latifolia and I. dabieshanensis ‘Ning Qing 3’ is special for its peculiar oblong leaf morphology (Chong et al. 2023). Ilex dabieshanensis ‘Ning Qing 1’ is unique as a result of its leathery leaf texture, broadly ovate leaf shape, and shiny blackish green (RHS 146A) leaf color. For I. dabieshanensis ‘Ning Qing 4’, the pyramid-shaped tree form and elliptic serrated leaves make it distinctive. In addition to leaf attributes, holly plants are usually arbor-like, whereas germplasm grown with a dwarf tree habit is relatively rare.

‘Ning Qing 2’ was selected and released by the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Memorial Sun Yat-Sen). The cultivar is male and very popular for home landscaping because of its dwarf tree habit, leathery leaf texture, small leaf size, serrated leaf margins, and greyish olive green (RHS NN137B) leaf color, enriching Ilex germplasm diversity significantly.

Origin

In Spring 2014, I. dabieshanensis (♀) was crossbred with I. latifolia (♂) at the Repository of Ilex spp. Germplasm, Nanjing Botanical Garden Memorial Sun Yat-Sen, Jiangsu, China (lat. 32°03'N, long. 118°49'E). More than 500 cross-pollinated seeds were collected in winter and then stored in semihumid sand to break dormancy. In Spring 2015, seeds were sown in a seedbed with a perlite and peat mixture as the substrate. After germination, seedlings were transplanted into the field with a 30- × 30-cm spacing. In May 2017, an unusual dwarf seedling with small, leathery, serrated, and greyish olive green (RHS NN137B) leaves was observed and selected for further evaluation. It was named ‘Ning Qing 2’. After 5 years of semihardwood/hardwood cutting propagation evaluations (2018–22) and 6 years of field observation (2018–23), the rooted cuttings represented the same morphological attributes as the mother plant, confirming their phenotypic stability. Notably, the cuttings grew vigorously in Jiangsu (lat. 32°03'N, long. 118°49'E; approximately US Department of Agriculture plant hardiness zones 9b/10a), even under considerably high (37–40 °C) and low (–5 to 0 °C) temperatures. To date, no diseases or pests are of major concern. The cultivar was authorized by the Forest Variety Certification Committee of China in 2023.

Description

Compared with its parents (I. dabieshanensis and I. latifolia), the distinguishing characteristics of ‘Ning Qing 2’ are its dwarf tree habit, leathery leaf texture, small leaf size, serrated leaf margins, and greyish olive green (RHS NN137B) leaf color (Table 1, Fig. 1). The specific attributes of ‘Ning Qing 2’ are described next.

Table 1.

Phenotypic comparisons of Ilex ‘Ning Qing 2’, Ilex dabieshanensis, and Ilex latifolia.

Table 1.
Fig. 1.
Fig. 1.

Comparison of leaf attributes among Ilex ‘Ning Qing 2’ (left), Ilex dabieshanensis (middle), and Ilex latifolia (right).

Citation: HortScience 59, 1; 10.21273/HORTSCI17490-23

Habit.

In general, 3-year-old I. dabieshanensis and I. latifolia can respectively reach up to 1.2 m and 0.9 m, respectively, in height. ‘Ning Qing 2’ is evergreen and dwarf (Fig. 2A), with a narrow canopy of ∼0.8 m in tree height and 0.4 m in crown diameter until 7 years of age (Fig. 2B).

Fig. 2.
Fig. 2.

Phenotypic characteristics of Ilex ‘Ning Qiang 2’. (A) Dwarf rooted cutting at 4 years of age. (B) Upright growth habit with a semiopen canopy. (C) Reddish orange [Royal Horticultural Society (RHS) 43A] young leaves and yellowish green (RHS 143B) twigs covered with white lenticels. (D) Small, elliptic, serrated, and grayish olive green (RHS NN137B) mature leaves.

Citation: HortScience 59, 1; 10.21273/HORTSCI17490-23

Stems and foliage.

The stems are yellowish green (RHS 143B) and 2 to 4 mm in diameter and are covered with white lenticels. The mature leaves are leathery and greyish olive green (RHS NN137B), transformed from the reddish orange (RHS 43A) thin, leathery, young-developing, expanding leaves (Fig. 2C). Leaf blades are elliptic and small (3.5–4.5 cm in length × 1.5–2.0 cm in width), connected with short petioles (0.4–0.5 cm), with six to seven pairs of serrations at their edges. Leaf bases are cuneiform, whereas the apexes are acuminate (Fig. 2D).

Flower.

Greenish yellow flowers (RHS 145B) are axillary and grow inconspicuously on the current year’s branchlets. Each flower has four petals that are obovate-oblong (3.9–4.0 mm in length × 2.1–2.3 mm in width) and slightly connate basally. Four stamens and a degenerate pistil are inside the petals (Fig. 2B). In Jiangsu Province, the plant starts to blossom in late April and the flowering period can last for about 12 d.

Propagation

For ‘Ning Qing 2’ clonal propagation, the methods of semihardwood stem cuttings (June–July in Jiangsu) and hardwood stem cuttings (late November–late March before sprouting) are usually recommended. For semihardwood stem cutting, the current year’s semilignified branches should be chosen and cut into short cuttings (∼6–10 cm long), with two to three half leaves kept at the top. For hardwood cuttings, it was better to select thick and healthy annual branches, and then cut them into cuttings of 10 to 15 cm in length, with an approximate cutting depth of 4 to 6 cm. For better survival, it is suggested one use 2000 ppm indole-3-butyric acid and treat the cuttings for 8 to 10 s in advance, and then insert them into the substrate, kept in moderate humidity, and place them under sprinkler irrigation. In general, the cuttings will root after 30 d, and the rooting percentage can reach up to 90%.

Cultivation

‘Ning Qing 2’ prefers a fully illuminated environment and can also tolerate semishade conditions. Acidic soil is beneficial for the cultivation of ‘Ning Qing 2’. In early spring, transplantation with the soil ball is suggested, followed by thorough irrigation. As a result of the slow growth rate of this cultivar, little structural pruning of the plant is needed. During the past 7 years, no serious pests and diseases have been observed.

Availability

The plant ‘Ning Qing 2’ is available from Dr. Chen Hong (chenhong@cnbg.net), 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 leaf attributes among Ilex ‘Ning Qing 2’ (left), Ilex dabieshanensis (middle), and Ilex latifolia (right).

  • Fig. 2.

    Phenotypic characteristics of Ilex ‘Ning Qiang 2’. (A) Dwarf rooted cutting at 4 years of age. (B) Upright growth habit with a semiopen canopy. (C) Reddish orange [Royal Horticultural Society (RHS) 43A] young leaves and yellowish green (RHS 143B) twigs covered with white lenticels. (D) Small, elliptic, serrated, and grayish olive green (RHS NN137B) mature leaves.

  • 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
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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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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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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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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Xiaolong Cai 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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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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Contributor Notes

This study was funded by the Central Finance Forestry Science and Technology Promotion Demonstration Subsidy Project (SU[2023]TG08), the Opening Project of Zhejiang Provincial Key Laboratory of Forest Aromatic Plants-based Healthcare Functions (SLFX-202205), the National Natural Science Foundation of China (32201618), and the Natural Science Foundation of Jiangsu Province (Grants No BK20220751).

T.Z. is the corresponding author. E-mail: tingzhou689@cnbg.net.

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  • Fig. 1.

    Comparison of leaf attributes among Ilex ‘Ning Qing 2’ (left), Ilex dabieshanensis (middle), and Ilex latifolia (right).

  • Fig. 2.

    Phenotypic characteristics of Ilex ‘Ning Qiang 2’. (A) Dwarf rooted cutting at 4 years of age. (B) Upright growth habit with a semiopen canopy. (C) Reddish orange [Royal Horticultural Society (RHS) 43A] young leaves and yellowish green (RHS 143B) twigs covered with white lenticels. (D) Small, elliptic, serrated, and grayish olive green (RHS NN137B) mature leaves.

 

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