Appearance of Phalaenopsis Hualien Pink Apple ‘Hualien No. 1-Pink Apple’. (A) Two flower spikes and early blooming in a 7.6-cm pot. (B) Light red–purple flower with fragrance. (C) Uniform blooming performance in a greenhouse.
Fragrance composition of Phalaenopsis Hualien Pink Apple ‘Hualien No. 1-Pink Apple’. The composition was analyzed through gas chromatography–mass spectrometry.
Disease severity index (%) for Phalaenopsis equestris (EQ), Phal. Sogo Yukidian ‘V3’ (V3), and Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ (HPA) in the fifth week after inoculation with Fusarium phalaenopsidis.
Appearance of (A) Phalaenopsis equestris, (B) Phal. Sogo Yukidian ‘V3’, and (C) Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ in the fifth week after inoculation with Fusarium phalaenopsidis. Arrowheads point to inoculation incisions; bar = 1 cm.
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Phalaenopsis exhibit lower resistance to leaf-yellowing disease than Cymbidium, Cattleya, Dendrobium, and Oncidium (Benyon et al. 1996; Chung et al. 2011; Ichikawa and Heideki 1998; Latiffah et al. 2009). Leaf-yellowing disease in phalaenopsis, primarily caused by Fusarium phalaenopsidis (formerly F. solani f. sp. phalaenopsis), is a major cause of post-shipment losses on phalaenopsis exported from Taiwan via sea freight (Hsieh et al. 2007; Liao et al. 2012; Su et al. 2010). Although sea freight, which involves the transport of phalaenopsis, markedly reduces transportation costs, shipping from Taiwan to the United States typically takes 2 to 3 weeks (Hou et al. 2010). Because of the extended duration of sea freight, losses from leaf-yellowing disease during transit can exceed 30%. In some cases, phalaenopsis may already be carrying the disease pathogen before being loaded into shipping containers, but symptoms appear only after ∼30 d in transit, upon arrival at their destination (Hsieh 2012).
In phalaenopsis, leaf-yellowing disease leads to the rotting of leaf sheaths and roots, resulting in black rot in the leaf sheaths, yellowing of the lower leaves, and rapid shedding of the affected leaves (Su et al. 2010). The primary pathogens responsible for this disease in phalaenopsis belong to the genus Fusarium—for example, Fusarium phalaenopsidis, Fusarium oxysporum, and Fusarium proliferatum, with Fusarium phalaenopsidis being the most commonly isolated pathogen. In Taiwan, Fusarium phalaenopsidis infections reduce phalaenopsis yields by 20% to 30% annually (Su et al. 2010). This fungus typically invades the base of the stem or leaf sheath, manifesting disease symptoms 1 to 2 months after infection. By the time the symptoms of leaf-yellowing disease become apparent, the leaf sheath is often already extensively infected, making it challenging to determine the optimal time for disease control (Hsieh et al. 2007).
Enhancing host resistance to Fusarium infection and breeding disease-resistant varieties are key strategies for controlling Fusarium-related diseases in many crops (Chen et al. 2021; Goktepe et al. 2007; McGrath et al. 1987). Breeding cultivars with disease resistance capabilities may substantially improve market competitiveness. Recently, the Hualien Agricultural Research and Extension Station announced the release of Phalaenopsis Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ (HPA), a cultivar resistant to leaf-yellowing disease. This resistance helps minimize damage caused by the disease, reducing losses during sea freight.
Phalaenopsis Hualien Pink Apple was developed in May 2007 by crossing Phal. Leopard Prince ‘Sogo Diamond’ (seed parent) with Phal. Hualien Lit-Caroline ‘HF021#1’ (pollen parent). Mature hybrid seed capsules were surface-sterilized with 70% ethanol. Next, they were treated with 1.0% sodium hypochlorite solution for 20 min and then rinsed thrice with sterile distilled water. The capsules were cut open, and the seeds were extracted using forceps. The seeds were cultured on Murashige and Skoog medium (Murashige and Skoog 1962), containing half-strength macronutrients, full-strength micronutrients, 100 mg·L−1 inositol, 20 g·L−1 sucrose, 8 g·L−1 agar, and 1 g·L−1 activated charcoal. Seed cultures were incubated at 25 ± 1 °C under a 14-h photoperiod with a light intensity of 40 μmol·m−2·s−1. In 2009, the seedlings were removed from the culture flasks and transferred to sphagnum moss in a controlled greenhouse, where they remained until flowering. When the temperature exceeded 25 ± 1 °C, a pad-and-fan cooling system was automatically activated to regulate the environment. The hybrid population first flowered in Apr 2010 (pot diameter: 7.6 cm), and 11 individuals with desirable traits were selected for further observation. In the second year of flowering, an individual plant (H021#4) produced 37 pink flowers (Fig. 1), exhibiting traits such as double spikes, numerous flowers, round-shaped flowers, vigorous growth, and fragrance. This plant was selected for vegetative propagation, and the grex was registered as Phal. Hualien Pink Apple with the Royal Horticultural Society (RHS). The distinctiveness, uniformity, and stability of this cultivar were tested between 2014 and 2015. In 2016, the cultivar was officially named ‘Hualien No. 1-Pink Apple’. In 2018, the cultivar’s resistance to leaf-yellowing disease was evaluated through an inoculation test.
Citation: HortScience 60, 5; 10.21273/HORTSCI18521-25
The following plants were used for the inoculation test: Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’, Phal. equestris, and Phal. Sogo Yukidian ‘V3’. They were cultivated in a controlled greenhouse. Two incisions (width: 0.5 cm; depth: 0.5 cm) were made with a scalpel at the leaf sheath of the third or fourth leaf from the bottom. Then, Fusarium phalaenopsidis (TJP-2178-10) spore suspension (diluted to 105 colony-forming units/mL) was inoculated into each wound, with 250 μL of the suspension applied per incision. After inoculation, disease severity level (DSL) was recorded every week for 5 weeks. DSL was defined based on Su et al. (2012), with modifications to include seven levels:
Level 0: healthy plants with no symptoms
Level 1: black necrotic lesions at the inoculation site
Level 2: a single leaf exhibits yellowing (yellowed area <1/2)
Level 3: a single leaf exhibits severe yellowing (yellowed area >1/2)
Level 4: most leaves exhibit yellowing (yellowed area >1/2)
Level 5: diseased leaves have dropped
Level 6: red fungal spores are visible to the naked eye
The disease severity index (DSI) was calculated using the following formula, which is widely applied in disease assessment (Chiang et al. 2017): DSI (%) = {Σ (DSL × number of individuals in this DSL)/(maximal DSL × total number of individuals in the same cultivar)} × 100. The experiment was conducted in a completely randomized design, three replicates and six plants per replicate were used for each cultivar.
Phalaenopsis Hualien Pink Apple HPA exhibits dual flower spikes, early natural flowering, and a short interval from deflasking to first blooming. This cultivar can bloom in pots with a diameter of 7.6 cm (Fig. 1A) and has a low chilling requirement for flowering. The inflorescence is a raceme, with florets measuring ∼6 cm in vertical diameter and 7 cm in horizontal diameter. The dorsal sepal is predominantly red-purple [Royal Horticulture Society (RHS) N74D] with light spotting and striping. The lateral petals are also red-purple (RHS N74D) with similar light spotting and striping. The lip is red-purple (RHS 71B) but lacks spots (Fig. 1B). The plants exhibit stable, uniform blooming performance under greenhouse conditions (Fig. 1C). In commercial production, the blooming of phalaenopsis is typically regulated by either moving the plants to higher elevations for cooling or using air conditioning at lower elevations. The former approach incurs additional costs related to transport and handling, whereas the latter approach increases costs related to electricity and facilities. One of the valuable traits of the HPA cultivar is its ability to bloom naturally in January without requiring artificial forcing. This is a valuable trait because it can considerably reduce production costs by eliminating the need for cold forcing in highland areas or the reliance on air conditioning.
The HPA cultivar had a mild fragrance when it first bloomed during the single-individual selection process. Subsequent evaluations confirmed that this fragrance was stable. Fragrance analysis was performed at 9:00 AM on a sunny day using gas chromatography–mass spectrometry (QP-2010; Shimadzu, Tokyo, Japan), and the detected volatile compounds were compared against relevant databases (National Institute of Standards and Technology 27 and National Institute of Standards and Technology 147). The fragrance primarily consisted of monoterpenes, with ocimene (31%), citronellol (8%), citronellol acetate (24%), and nerol acetate (15.7%) being the primary contributors (Fig. 2).
Citation: HortScience 60, 5; 10.21273/HORTSCI18521-25
After inoculation with Fusarium phalaenopsidis spores, DSLs were recorded and categorized into seven levels (0 to 6). Phalaenopsis equestris, which has a more delicate leaf texture than the other two cultivars, is more susceptible to leaf-yellowing disease, with average DSLs of 0.6, 0.9, 1.4, 2.0, and 2.2 in weeks 1, 2, 3, 4, and 5, respectively (Fig. 3). Almost all inoculated plants of Phal. Sogo Yukidian ‘V3’, the most widely produced large white-flower cultivar in commercial settings, exhibited disease symptoms, with average DSLs of 0.6, 0.7, 0.7, 0.8, and 0.8 in weeks 1, 2, 3, 4, and 5, respectively. However, its average DSLs all remained below 1, indicating some degree of resistance to leaf-yellowing disease. HPA exhibited even stronger disease resistance, with an average DSL of 0.1 per week (Fig. 3). After 5 weeks, this HPA cultivar exhibited virtually no symptoms of leaf-yellowing disease. The DSI values after 5 weeks were 36.1%, 13.0%, and 0.9% for Phal. equestris, Phal. Sogo Yukidian ‘V3’, and HPA, respectively (Fig. 4). Therefore, HPA exhibited the highest level of resistance to leaf-yellowing disease. Plants employ both structural and biochemical defense mechanisms to resist pathogen invasion. When a Fusarium pathogen infects a plant, it first compromises the structural defense system of the host and then produces host-specific mycotoxins to overcome the plant’s biochemical defense system (Perincherry et al. 2019). The inoculation test performed in this study involved creating wounds, thereby bypassing the structural defense system, to assess biochemical resistance in phalaenopsis. The results indicated that the severity of leaf-yellowing disease was substantially lower in Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ than in the other cultivars (Fig. 5). Therefore, Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ not only possesses dual flower spikes and fragrance but also exhibits superior resistance to leaf-yellowing disease.
Citation: HortScience 60, 5; 10.21273/HORTSCI18521-25
Citation: HortScience 60, 5; 10.21273/HORTSCI18521-25
Citation: HortScience 60, 5; 10.21273/HORTSCI18521-25
A Community Plant Variety Rights Certificate for the Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ (HPA) cultivar was granted by the Community Plant Variety Office (CPVO, France) in 2018. A limited quantity of plantlets is available for research purposes upon request to Yu-Che Yeh at the Hualien District Agricultural Research and Extension Station, Ministry of Agriculture, Taiwan.
Appearance of Phalaenopsis Hualien Pink Apple ‘Hualien No. 1-Pink Apple’. (A) Two flower spikes and early blooming in a 7.6-cm pot. (B) Light red–purple flower with fragrance. (C) Uniform blooming performance in a greenhouse.
Fragrance composition of Phalaenopsis Hualien Pink Apple ‘Hualien No. 1-Pink Apple’. The composition was analyzed through gas chromatography–mass spectrometry.
Disease severity index (%) for Phalaenopsis equestris (EQ), Phal. Sogo Yukidian ‘V3’ (V3), and Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ (HPA) in the fifth week after inoculation with Fusarium phalaenopsidis.
Appearance of (A) Phalaenopsis equestris, (B) Phal. Sogo Yukidian ‘V3’, and (C) Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ in the fifth week after inoculation with Fusarium phalaenopsidis. Arrowheads point to inoculation incisions; bar = 1 cm.
Contributor Notes
This study is a part of the dissertation submitted by Yu-Che Yeh in partial fulfillment of doctoral degree requirements.
Appearance of Phalaenopsis Hualien Pink Apple ‘Hualien No. 1-Pink Apple’. (A) Two flower spikes and early blooming in a 7.6-cm pot. (B) Light red–purple flower with fragrance. (C) Uniform blooming performance in a greenhouse.
Fragrance composition of Phalaenopsis Hualien Pink Apple ‘Hualien No. 1-Pink Apple’. The composition was analyzed through gas chromatography–mass spectrometry.
Disease severity index (%) for Phalaenopsis equestris (EQ), Phal. Sogo Yukidian ‘V3’ (V3), and Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ (HPA) in the fifth week after inoculation with Fusarium phalaenopsidis.
Appearance of (A) Phalaenopsis equestris, (B) Phal. Sogo Yukidian ‘V3’, and (C) Phal. Hualien Pink Apple ‘Hualien No. 1-Pink Apple’ in the fifth week after inoculation with Fusarium phalaenopsidis. Arrowheads point to inoculation incisions; bar = 1 cm.
