Crape myrtles (Lagerstroemia) are important ornamental woody plants with ∼55 species and at least 500 identified cultivars that are valued because of their diverse tree habits, long-lasting midsummer blooms, and rich flower colors (Cai et al. 2011; Qin et al. 2021; Roy et al. 2015; Ye et al. 2019). However, only a limited number of these taxa, such as L. stenopetala, L. caudata, L. ‘Xiang Xue Yun’, and L. ‘Bai Mi Xiang’, have fragrances among the extant resources (Zhang et al. 2007). Most members of the Lagerstroemia genus have no odor, which reduces their economic value. Since the 1960s, large-scale crape myrtle breeding focused primarily on disease resistance, tree habits, flower/leaf color, and flower shape has been conducted in China and abroad (Hu et al. 2019; Li et al. 2015; Toki and Katsuyama 2008; Wang et al. 2013). However, few efforts have been made to improve the floral scent.
The floral scent is desirable for ornamental plants and cut flowers (Xiang and Chen 2009). For some species, the floral scent influences consumers more than the flower color or shape (Sexton et al. 2005). Therefore, developing new charming Lagerstroemia cultivars with pleasing aromas is highly significant. ‘Ning Xiang 2’ was selected and released by the Institute of Botany, Jiangsu Province and Chinese Academy of Sciences (Nanjing Botanical Garden Mem. Sun Yat-Sen). The rose-like fragrance of its brilliant red–purple (RHS 67B) (Royal Horticultural Society 2015) flowers has sparked much interest, thus enriching Lagerstroemia aromatic germplasm resources and significantly improving their ornamental values. To date, no serious pests or diseases have been observed. The cultivar is suitable for landscaping public places, such as parks and plazas, and planting in public areas, such as streets and courtyards.
Origin
During Summer 2014, L. fauriei (♀) was crossbred with L. ‘Tuscarora’ (♂) at the Nanjing Botanical Garden, Jiangsu Province, China (32°03′N, 118°49′E). Then, more than 500 cross-pollinated seeds were collected in November for dry storage. In Spring 2015, seeds were sown in a seedbed (width: 1.5 m; length: 50 m; depth: 8.0–10.0 cm). After germination, seedlings were transplanted in the field with 20.0- × 20.0-cm spacing. In Spring 2018, ‘Ning Xiang 2’, a single plant with brilliant red–purple (RHS 67B) flowers and a rose-like fragrance, was identified and selected for further evaluation. After 2 years of softwood/hardwood cutting (2018–19) and 5 years of successive observations (2018–22), more than 60 young cuttings produced the exact morphological characteristics of the mother (donor) plant, thus confirming their phenotypic stability. The seedlings grew vigorously and exhibited good tolerance to high (37 to 40 °C) and low temperatures (4 to 6 °C) in Jiangsu, and few incidents of brown spot, sooty blotch, and aphids were observed. This cultivar was authorized by the Forest Variety Certification Committee of China in 2022.
Description
Among existing Lagerstroemia germplasms, ‘Ning Xiang 2’ is most similar to ‘Fen Jing’, which was also released by Nanjing Botanical Garden in 2022. ‘Fen Jing’ is characterized by conical buds grown with an apical protuberance, whereas cylindrical buds with no apical protuberance are characteristics of ‘Ning Xiang 2’. Additionally, the floral fragrances of the two cultivars are distinct, with Fen Jing being odorless and Ning Xiang 2 having a rose-like fragrance (Table 1 and Supplemental Fig. S1). Furthermore, another existing control cultivar with fragrance is Ning Xiang 1, which was also released by Nanjing Botanical Garden in 2022. The main fragrance components of ‘Ning Xiang 1’ and ‘Ning Xiang 2’ are similar, including methyl geranate, (±)-2,3-dihydrofarnesol, and (E,E)-farnesal. ‘Ning Xiang 1’ has purple–violet (RHS N81D) flowers, whereas ‘Ning Xiang 2’ has red–purple (RHS 67B) flowers (Table 1 and Supplemental Fig. S1). The specific characteristics of ‘Ning Xiang 2’ are presented (Table 2).
Comparison of phenotypic attributes of ‘Fen Jing’, ‘Ning Xiang 2’, and ‘Ning Xiang 1’.
Phenotypic characteristics of ‘Ning Xiang 2’.
Tree.
The ‘Ning Xiang 2’ tree is arbor-like and can attain a height of 2.0 m with a 1.3-m spread at 4 years of age. It has a red trunk with reddish-brown branches forming the canopy and is semi-upright (Supplemental Fig. S2A).
Twigs and Foliage.
The twigs are red (RHS 46C) and four-edged; furthermore, they are covered with short wings and sparse pubescence. The leaves are papery and elliptical (6.0–6.5 cm in length × 4.0–4.5 cm in width), and they are connected with short petioles (0.3–0.4 cm). The leaves turn from red (RHS 50A) in early spring to green (RHS NN137A) in midsummer (Supplemental Fig. S2B). Low-density pubescence covers the subsurface of the leaves.
Flower.
The flowering time (10% open flowers) of ‘Ning Xiang 2’ is medium (approximately mid-July in Jiangsu, China) and can last for ∼3 months (July–September). The cultivar has red (RHS 39B) and cylindrical buds (length, 0.8–1.0 cm; width, 0.6–0.7 cm) with weakly raised sutures and apical protuberance. The inflorescence is conical, comprising brilliant red–purple (RHS 67B) flowers (4.5–5.0 cm) with numerous yellow stamens (35–40). The flower has a rose-like fragrance, mainly containing methyl geranate, (±)-2,3-dihydrofarnesol, and (E,E)-farnesal components. Similar to many Lagerstroemia cultivars, Ning Xiang 2 features wrinkled petals (Supplemental Fig. S2C). The slender claws (0.7–0.9 cm) connected with petals are grown and have a red–purple color (RHS 67B).
Fruit.
‘Ning Xiang 2’ young fruits are green (RHS 141C), circular, and medium (vertical diameter: 1.4–1.6 cm; horizontal diameter: 1.2–1.5 cm). When mature or dry, the fruits turn brown (RHS 200A) (Supplemental Fig. S2D).
Cultivation
‘Ning Xiang 2’ is primarily regenerated through softwood cutting (July–August) or hardwood cutting (late March–early April before sprouting). For softwood cutting, semi-lignified branches should be selected and cut into short cuttings (∼10 cm in length) with two to three half leaves retained at the top; however, for hardwood cutting, thick annual branches should be selected and cut into cuttings 10 to 15 cm in length, with a cutting depth of ∼8 to 13 cm. Subsequently, the cuttings should be thoroughly irrigated. A plastic film layer should be placed on the seedbed to trap moisture and heat, and a shading net should be built for shading. Generally, the cuttings can root within ∼15 to 20 d and reach ∼70 cm in length during that year after removing the film, keeping the shading net, and proper watering during the growth period.
Brown spots, sooty blotch, and aphids rarely cause damage to young shoots and leaves. To prevent brown spot formation, leave surfaces can be sprayed with 50% carbendazim wettable powder at 500× dilution. To prevent sooty blotches, leave surfaces can be sprayed with 40% omethoate at 1000× dilution. To prevent aphids, surface leaves should be sprayed with 50% pirimicarb at 3000× dilution.
Availability
The relevant plant material and research information of ‘Ning Xiang 2’ can be obtained from Dr. Chen, Institute of Botany, Jiangsu Province, and the Chinese Academy of Sciences (Nanjing Botanical Garden Memorial Sun Yat-Sen).
References Cited
Cai, M, Pan, HT, Wang, XF, He, D, Wang, XY, Wang, XJ & Zhang, QX 2011 Development of novel microsatellites in Lagerstroemia indica and DNA fingerprinting in Chinese Lagerstroemia cultivars Scientia Hort. 131 88 94 https://doi.org/10.1016/j.scienta.2011.09.031
Hu, L, Zheng, TC, Cai, M, Pan, HT, Wang, J & Zhang, QX. 2019 Transcriptome analysis during floral organ development provides insights into stamen petaloidy in Lagerstroemia speciosa Plant Physiol Biochem. 142 510 518 https://doi.org/10.1016/j.plaphy.2019.08.012
Li, Y, Zhang, ZY, Wang, P, Wang, SA, Ma, LL, Li, LF, Yang, RT, Ma, YZ & Wang, Q. 2015 Comprehensive transcriptome analysis discovers novel candidate genes related to leaf color in a Lagerstroemia indica yellow leaf mutant Genes Genomics. 37 851 863 https://doi.org/10.1007/s13258-015-0317-y
Qin, B, Sun, K & Huang, X. 2021 The complete chloroplast genome of Lagerstroemia balansae, an endangered species of genus Lagerstroemia native to China Mitochondrial DNA B Resour. 6 684 685 https://doi.org/10.1080/23802359.2021.1882352
Royal Horticultural Society 2015 RHS colour chart 6th ed. Royal Horticultural Society London, UK
Roy, RK, Khuraijam, JS & Singh, S. 2015 Lagerstroemia for urban landscapes in India Int J Sci Res. 4 164 165 https://doi.org/10.31220/osf.io/zw2uj
Sexton, R, Stopford, AP, Moodie, WT & Porter, AEA. 2005 Aroma production from cut sweet pea flowers (Lathyrus odoratus): The role of ethylene Physiol Plant. 124 381 389 https://doi.org/10.1111/j.1399-3054.2005. 00498.x
Toki, K & Katsuyama, N. 2008 Pigments and colour variation in flowers of Lagerstroemia indica J Jpn Soc Hortic Sci. 63 853 861 https://doi.org/10.2503/jjshs.63.853
Wang, JF, Liu, XH & Chen, ZM. 2013 Research progress in breeding of Lagerstroemia plant Yuan Yi Xue Bao. 40 1795 1804
Xiang, L & Chen, L. 2009 Advances in genetic engineering of floral scent Zhongguo Nong Ye Ke Xue. 42 2076 2084
Ye, YJ, Feng, L, Liang, XH, Liu, TT, Cai, M, Cheng, TR, Wang, J, Zhang, QX & Pan, HT. 2019 Characterization, validation, and cross-species transferability of newly developed EST-SSR markers and their application for genetic evaluation in crape myrtle (Lagerstroemia spp) Mol Breed. 39 26 https://doi.org/10.1007/s11032-019-0936-0
Zhang, J, Wang, LS, Zhang, JJ, Shu, QY & Gao, JM. 2007 Advances in studies on genus Lagerstroemia Yuan Yi Xue Bao. 34 251 256
Comparison of floral attributes of (A) ‘Fen Jing’, (B) ‘Ning Xiang 2’, and (C) ‘Ning Xiang 1’.
Citation: HortScience 58, 2; 10.21273/HORTSCI16902-22
Comparison of floral attributes of (A) ‘Fen Jing’, (B) ‘Ning Xiang 2’, and (C) ‘Ning Xiang 1’.
Citation: HortScience 58, 2; 10.21273/HORTSCI16902-22
Comparison of floral attributes of (A) ‘Fen Jing’, (B) ‘Ning Xiang 2’, and (C) ‘Ning Xiang 1’.
Citation: HortScience 58, 2; 10.21273/HORTSCI16902-22
Phenotypic characteristics of ‘Ning Xiang 2’. (A) Semi-upright growth habit. (B) New red leaves and twigs. (C) Red buds and bright red–purple (RHS 67B) flowers. (D) Young and mature fruits.
Citation: HortScience 58, 2; 10.21273/HORTSCI16902-22
Phenotypic characteristics of ‘Ning Xiang 2’. (A) Semi-upright growth habit. (B) New red leaves and twigs. (C) Red buds and bright red–purple (RHS 67B) flowers. (D) Young and mature fruits.
Citation: HortScience 58, 2; 10.21273/HORTSCI16902-22
Phenotypic characteristics of ‘Ning Xiang 2’. (A) Semi-upright growth habit. (B) New red leaves and twigs. (C) Red buds and bright red–purple (RHS 67B) flowers. (D) Young and mature fruits.
Citation: HortScience 58, 2; 10.21273/HORTSCI16902-22
