Crabapples (Malus spp.) are small trees and shrubs in the rose family that are valued for their various types of flowers (single, semi-double, and double forms in shades of purple, red, pink, and white), colorful, small fruits (≤5 cm; primarily purple, red, pink, orange, yellow, and green), and diverse growth habits (columnar, fastigiate, upright, spreading, drooping, weeping) (UPOV, 2003; Wyman, 1955). They also have an added advantage of wide environmental adaptability, thus facilitating their worldwide prominence as the focal points of landscapes and gardens. Although nearly 1200 Malus taxa are recorded in Fiala’s Flowering Crabapple (Fiala, 1994), less than 5% are semi-double or double-flowered, such as the outstanding ‘Brandywine’ (pink doubles), ‘Kelsey’ (red doubles), and ‘Sparkler’ (red-purple semi-doubles), resulting in a scarcity of double-type cultivars currently available. Additionally, petal colors of these existing double germplasm often fade easily, which significantly shortens their ornamental periods. Crabapple breeding is an active endeavor worldwide, with increasing efforts dedicated toward the rare double-flowered germplasm. During the 20th century, breeding of flowering crabapples was mainly performed in Canada and the United States, where ≈400 to 600 different forms and cultivars were grown (Dirr, 2010). However, for the past 20 years, only four new double-flowered crabapple cultivars—‘Spring Bride’ (white-flowered) (Spongberg, 1996), ‘Jarmin’ (pink-flowered) (Jarmin, 2003), ‘Fenghong Nichang’ (pink-flowered) (Fan et al., 2019), and ‘Fen Balei’ (pink-flowered) (Zhou et al., 2019)—have been documented on the U.S. market.
Plant phenotypes display extremely high variations in size, color, structure, and function, which are the products of continuous remodeling to adapt to different environmental conditions and pollinators, and the important foundations for germplasm innovations (Dudash et al., 2011; Endress, 2011; Kumari et al., 2016; Mojica and Kelly, 2010; Santos et al., 2011). Therefore, it is of great importance to breed new crabapple cultivars with novel flower forms and colors. Malus ‘Zi Dieer’ was selected and released from the Nanjing Forestry University’s crabapple breeding program. This cultivar has gained much attention for its double and nonfadable red-purple flowers, which enriched double germplasm resources in Malus and significantly prolonged their ornamental periods (12–15 d). To date, no serious pests or diseases have been observed. Damage to young tips and leaves caused by apple aphids, spider mites, and apple rust is rare. The cultivar is suitable for street trees, courtyard greening, park landscaping, and other theme attraction construction. We report the development and selection of the ‘Zi Dieer’ crabapple cultivar.
DirrM.2010Manual of woody landscape plants. 6th ed. Stipes Publishing Champaign IL
DudashM.R.HasslerC.StevensP.M.FensterC.B.2011Experimental floral and inflorescence trait manipulations affect pollinator preference and function in a hummingbird-pollinated plantAmer. J. Bot.98275282
FialaJ.L.1994Flowering crabapples: The genus Malus p. 106–273. Timber Press Portland OR
JarminM.2003Crabapple tree named ‘Jarmin’. U.S. Patent Application no. 09/997044
KumariJ.BagM.K.PandeyS.JhaS.K.ChauhanS.S.JhaG.K.GautamN.K.DuttaM.2016Assessment of phenotypic diversity in pearl millet [Pennisetum glaucum (L.) R. Br.] germplasm of Indian origin and identification of trait-specific germplasmCrop Pasture Sci.6712231234
MojicaJ.P.KellyJ.K.2010Viability selection prior to trait expression is an essential component of natural selectionProc. Biol. Sci.27729452950
Royal Horticultural Society2007RHS colour chart. 5th ed. Royal Horticultural Society London UK
SantosE.A.SouzaM.M.VianaA.P.AlmeidaA.A.FreitasJ.C.LawinsckyP.R.2011Multivariate analysis of morphological characteristics of two species of passion flower with ornamental potential and of hybrids between themGenet. Mol. Res.1024572471
UPOV2003Guidelines for the conduct of tests for distinctness uniformity and stability [ornamental apple (Malus Mill.)]. TG/192/1
WymanD.1955Trees for American gardens. Macmillan New York NY