Ornamental crabapple is a woody species in the genus Malus of the Rosaceae family, which has been widely cultivated for its ornamental and economic value (Wan et al. 2015; Zhao et al. 2014). It is planted mainly in temperate regions and often symbolizes good things in Chinese painting, poetry, and garden art (Guo et al. 2019). As a popular landscape plant, the ornamental value of crabapple is found in the delightful spring flowers and attractive fruit in fall and winter (Lu et al. 2015).
The book Flowering Crabapples recorded more than 1200 crabapple germplasms (Fiala 1994), among which were a large amount of pink and green leaf cultivars, such as Yellow Jade, Bride, and Molten Lava. In addition, there are many types of pink flowers in crabapple germplasms, such as ‘Fenghong Nichang’, ‘Fen Balei’, ‘Zi Dieer’, and ‘Juan Zhulian’ (Fan et al. 2019; Zeng et al. 2022; Zhou et al. 2019, 2020). However, there are few cultivars with bright-pink flowers in sharp contrast to emerald leaves. There is demand for cultivars with new and unique flower and leaf color combinations. In response to this demand, we introduce a new crabapple cultivar, Yanzhi Yu, that has bright-pink flowers and glossy leaves.
Origin
Malus.
‘Yanzhi Yu’ is a new cultivar of crabapple bred by natural hybridization. In Autumn 2011, more than 8000 seeds of nine crabapples (Malus ×zumi ‘Calocarpa’, ‘Indian Summer’, ‘Purple Prince’, ‘Donald Wyman’, ‘Red Jade’, ‘Qian Cengjin’, ‘Harvest Gold’, ‘Sugar Tyme’, and ‘Cinderella’) were collected from the National Crabapple Germplasm Genetic Center in Yangzhou City (lat. 32°42′N, long. 119°55'E). The cleaning procedure included soaking the seeds in warm water (40 to 45 °C) to soften the seedcoat. The seeds were placed in the moist sand medium (–5 to –10 °C) for 1 month. The seeds were sown in the seedbed in Spring 2012, and then the germinating seedlings were transplanted into the field after growing for 1 year.
One specific single plant was selected from 2013 to 2015. It had green leaves, yellow-orange fruit, and pink flowers. The flowers showed strong color rhythmicity. The petals at the initial blooming stage were pink, they were light pink at the full blooming stage, and the petals were nearly white at the final blooming stage. Bright-pink flowers and green leaves form a sharp contrast to the characteristics of this excellent ornamental. From 2015 to 16, two generations of the individual were propagated by bud-grafting. The flower traits of the grafted seedlings were observed for 2 years and were found to be stable. Each individual plant had vigorous vegetative growth and had good adaptivity to high temperatures (37 to 40 °C).
Description
Specific characteristics of ‘Yanzhi Yu’ are bright-pink flowers and green leaves. There are significant differences between ‘Yanzhi Yu’ and the approximate species Malus floribunda in tree habit, flower shape, petal position (relative to margins), flattened petal diameter, and length of fruit peduncle between both cultivars. Malus floribunda is characterized by a spreading growth habit (reaching a height of 4.0 m and a width of 2.5 m), a deep-cup flower shape, free petals, small flower size (2.8–3.6 cm), and a long fruit peduncle length (2.6–3.4 cm). ‘Yanzhi Yu’ has an upright tree habit (reaching a height of 4.0 m and a width of 2.0 m), a shallow-cup flower shape, overlapping petals, large flower size (4.4–5.6 cm), and a medium fruit peduncle length (1.9–2.3 cm) (Table 1). The distinguishing features of ‘Yanzhi Yu’ are described next.
Comparisons of phenotypic characteristics between Malus ‘Yanzhi Yu’ and Malus floribunda.
Habit.
The individual plant has an upright growth habit with brownish red branches (Table 1, Fig. 1A).
Phenotypic characteristics of Malus ‘Yanzhi Yu’ crabapple. (A) The growth habit at the beginning of the flowering stage. (B, C) Flowering branch with flowers at full bloom. (D) The different flowering stages of ‘Yanzhi Yu’: (a) flower bud stage and (b) back view of mature flower. (E) Mature fruit: (a) front view of infructescence and (b) fruit pulp. (F) Leaf morphology: (a) front view of leaf and (b) back view of leaf.
Citation: HortScience 58, 5; 10.21273/HORTSCI17126-23
Phenotypic characteristics of Malus ‘Yanzhi Yu’ crabapple. (A) The growth habit at the beginning of the flowering stage. (B, C) Flowering branch with flowers at full bloom. (D) The different flowering stages of ‘Yanzhi Yu’: (a) flower bud stage and (b) back view of mature flower. (E) Mature fruit: (a) front view of infructescence and (b) fruit pulp. (F) Leaf morphology: (a) front view of leaf and (b) back view of leaf.
Citation: HortScience 58, 5; 10.21273/HORTSCI17126-23
Phenotypic characteristics of Malus ‘Yanzhi Yu’ crabapple. (A) The growth habit at the beginning of the flowering stage. (B, C) Flowering branch with flowers at full bloom. (D) The different flowering stages of ‘Yanzhi Yu’: (a) flower bud stage and (b) back view of mature flower. (E) Mature fruit: (a) front view of infructescence and (b) fruit pulp. (F) Leaf morphology: (a) front view of leaf and (b) back view of leaf.
Citation: HortScience 58, 5; 10.21273/HORTSCI17126-23
Flower.
The flowering time of ‘Yanzhi Yu’ starts near 8 Apr and lasts for 10 d in Jiangsu Province, China. The flower has an umbrella inflorescence with red-purple buds and red flower stalks. The petals are oval and have prominent veins. The diameter of the petals is uniform (4.4–5.6 cm). The middle zone of the petal is red-purple [Royal Horticultural Society (RHS) 69B] and the base color is white (RHS 155C) (Royal Horticultural Society 2007) (Table 1, Fig. 1B–D).
Fruit.
The fruit is subspherical and the main color is yellow-orange (RHS 18A), with yellow flesh (RHS 6D). The fruit diameter is small and the length of the fruit peduncle is medium (1.9–2.3 cm) (Fig. 1E). The set of fruit is large and it has a long fruit period (from July to October).
Foliage.
The spreading blades are green, elliptic, and leathery. The leaves are of medium length (4.5–5.5 cm) and narrow width (1.5–2.5 cm), with a large length-to-width ratio (∼2.5). The leaf edge is circular serrated and the leaf surface is green with a medium luster (Fig. 1F).
Cultivation
‘Yanzhi Yu’ is propagated by bud-grafting and by using Malus hupehensis as the rootstock in autumn (August–September in Jiangsu). For grafting, scion buds were cut from the strong hardwood branches and were embedded with the xylem of the rootstock, then both rootstock and bud were bound by plastic film (Zhou et al. 2020). The plastic film can be removed after 30 d of grafting. ‘Yanzhi Yu’ is generally planted in the south of the Yangtze River Basin to the north of central Fujian (located in a subtropical monsoon climate with four distinct seasons). Compared with M. floribunda, ‘Yanzhi Yu’ has a relatively stronger resistance to diseases and pests. Aphids were found occasionally and controlled by spraying pesticide [50% Pimiricarb wettable powder (Kesheng, Yancheng, Jiangsu, China) at 2000× dilution].
Availability
‘Yanzhi Yu’ is available through Nanjing Forestry University and Yangzhou Crabapple Horticulture Limited Company (http://flowering-crabapple.njfu.edu.cn).
References Cited
Fan, JJ, Zhang, WX, Zhang, DL, Zhou, T, Jiang, H, Wang, GB & Cao, FL 2019 ‘Fenghong Nichang’ flowering crabapple HortScience. 54 1260 1262 https://doi.org/10.21273/HORTSCI13897-19
Fiala, JL 1994 Flowering crabapples: The genus Malus 106 273 Timber Press Portland, OR, USA
Guo, L, Cao, Y, Quan, J & Liu, BY 2019 Crabapple in China: Past, present, and future Acta Hortic. 1263 55 60 https://doi.org/10.17660/ActaHortic.2019.1263.6
Lu, YF, Zhang, LR, Wang, YR & Yao, YC 2015 Establishment of an efficient in vitro plantlet regeneration system from leaf explants of ornamental crabapple (Malus spp.) J Hortic Sci Biotechnol. 90 585 592 https://doi.org/10.1080/14620316.2015.11668718
Royal Horticultural Society 2007 RHS colour chart 5th ed Royal Horticultural Society London, UK
Wan, HH, Zhang, J, Song, TT, Tian, J & Yao, YC 2015 Promotion of flavonoid biosynthesis in leaves and calli of ornamental crabapple (Malus sp.) by high carbon to nitrogen ratios Front Plant Sci. 6 673 https://doi.org/10.3389/fpls.2015.00673
Zeng, J, Zhou, T, Zhang, DL & Zhang, WX 2022 A new flowering crabapple cultivar named Malus ‘Juan Zhulian’ HortScience. 57 933 934 https://doi.org/10.21273/HORTSCI16696-22
Zhao, J, Wang, R, Huang, CX, Mao, ZQ, Guo, L & Shen, X 2014 Taxonomic analysis of volatiles emitted by ornamental crabapple flowers Acta Ecol Ainica. 34 213 218 https://doi.org/10.1016/j.chnaes.2014.01.003
Zhou, T, Jiang, H, Zhang, DL, Fan, JJ, Zhang, L, Wang, GB, Zhang, WX & Cao, FL 2019 ‘Fen Balei’ crabapple HortScience. 54 1433 1434 https://doi.org/10.21273/HORTSCI14063-19
Zhou, T, Jiang, H, Zhang, WX, Zhang, DL, Fan, JJ, Zhang, QQ, Wang, GB & Cao, FL 2020 ‘Zi Dieer’ crabapple HortScience. 55 272 274 https://doi.org/10.21273/HORTSCI14590-19
