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Flowering, postharvest and storage physiology

Session 3

O-15

Long term storage of cut flowers

John M. Dole (john_dole@ncsu.edu), Nathan Jahnke, Jennifer Kalinowski North Carolina State University, Raleigh, NC, USA

Cut flower producers often need to cold store cut flowers to build up inventory for events, markets and holidays or to hold excessive production. Cut flower species are grouped into three categories based on chilling sensitivity: tropicals (12 to 16°C), sub-tropicals (2 to 8°C) and chilling tolerant species (0 to 2°C). Successful long term storage of cut flowers requires that the stems be high quality, disease free, properly treated prior to storage, properly packaged, and held at the coldest temperature possible for each species. For chilling-tolerant species, subzero storage shows promise for increasing the storage duration while maintaining quality. Cut Paeonia flowers stored for 16 weeks at −0.6°C showed no freezing injury and were higher quality (reduced percentage of flowers that failed to open and fewer deformed flowers) than those stored at 0.6°C. Pre-storage pulses using a commercial hydration solution for 2 hours at 4°C and 200 g·L−1 had no effect. Tulipa stems could be stored for up to six weeks with no reduction in vase life if held at −0.6°C with the bulb attached and then treated with floral solutions after storage. Iris × hollandica stems lasted longer and more fully opened when pre-pulsed with floral solution prior to six weeks of storage at −0.6°C. Subzero storage may also be effective for long-term storage of other perennial and bulbous cut flowers including Alstroemeria hybrids, Anemone coronaria, Campanula medium, Chrysanthemum hybrids, Dianthus caryophyllus, Lilium hybrids, Ranunculus hybrids and Rosa hybrids.

Keywords: acclimation, cold storage, pretreatment

O-16

Balancing of some endogenous phytohormone on growth and development of sacred lotus (Nelumbo nucifera Gaertn.) after spraying of GA3 application

Panupon Hongpakdee (panupon@kku.ac.th), Sornnarin Suangto, Chaiartid Inkham, Soraya Ruamrungsri

Khon Kaen University, Khon Kaen, Thailand 2Chiang Mai University, Chiang Mai, Thailand

Sacred lotus is an important cut floricultural crop in Thailand, which became dormant in mild winter and caused to non-year-round production. The poor growth in low-temperature conditions resulted in not enough flower market demand. The experiment aimed to clarify some strategies for improving quantity and quality of flowering in sacred lotus off-season production. The influence of gibberellic acid (GA3) application on the changes in contents of some endogenous phytohormones such as trans-Zeatin riboside (t-ZR), abscisic acid (ABA) and gibberellin-like substances (GLS), as well as on the growth and development of lotus was examined in complete randomized design (CRD). One-month old plants were treated with GA3 at 200 and 400 ppm. GA3 treatment, regardless of the concentration, increased leaf number, leaf stalk length, and stolon length. Nevertheless, no effects of GA3 application on flower quality and number were observed. Plants treated with 400 ppm of GA3 showed the highest t-ZR content in stolon and trend to reduce GLS in plant parts compared to control plants. Increasing GA3 concentration reduced ABA content in leaves, but not in nodes. These findings on balancing of endogenous phytohormone might be beneficial for applying the PGRs to control flowering in further aspects.

Keywords: ABA, flowering, gibberellin-like substances, off-season sacred lotus, t-ZR

O-17

Reblooming in perennials: bearded iris (Iris germanica) as a model

Zhuping Fan (zhuping_fan@foxmail.com), Yike Gao, Rong Liu, Chunjing Guan

Leibniz Institue of Vegetable and Ornamental Crops, Grossbeeren, Germany 2Beijing Forestry University, Beijing, China

Reblooming, also known as continuous flowering, is common in the genus of Rosa, Fragaria and Iris. The reblooming perennials could bloom out of season, giving them more reproduction chances and extended ornamental stages. Bearded iris (Iris germanica) is a widely-used ornamental perennial, and the reblooming ones could annually bloom in spring and autumn. To reveal its molecular mechanisms of reblooming could provide important reference to the continuous flowering research in other perennials. In this presentation, our recent research results on reblooming bearded iris will be discussed. Specifically, through hybridization and phenotypic character analysis, transcriptome sequencing, transgenic analysis and genome editing, we analyzed the genetic law of ornamental characters in reblooming populations, and characterized the functions of flowering-related genes, thereby laying the theoretical foundation for the breeding of reblooming perennials.

Keywords: bearded iris, continuous flowering, genetic law, reblooming

O-18

De-vernalization – when heat erases flower induction

Michele Zaccai (mzaccai@bgu.ac.il), Hagai Yasuor, Ran Bar, Yair Nishri, Silit Lazare

Ben Gurion University, Beer Sheva, Israel
Agricultural Research Organization, The Volcani Institute, Israel 3Central and Northern Arava R&D Center, Arava Sapir, Israel

De-vernalization is the process leading to the delay or total inhibition of flowering in vernalized plants. This phenomenon takes place after planting under high temperatures and its meaning is the actual reversion of flower induction acquired by the plant during cold exposure. De-vernalization occurs in both annual and perennial plant species and can even be used a means to avoid flowering, like in onion. How can this happen? The mechanism of de- vernalization has been elucidated in only a small number of plants, like wheat and Arabidopsis, revealing differential expression of master flowering inhibitors achieved by epigenetic modifications. Typically, bulbs and corms grown for flower production undergo appropriate forcing and vernalization treatments in the summer and are planted in autumn. In these crops, the occurrence of de-vernalization generating a delay or complete revocation of flowering is increasing, due to the constant rise in autumn temperatures. These features have a major detrimental effect on flower production, yet the regulation of de-vernalization in flowering bulbs is far from being elucidated. In bulbs and corms, higher temperatures at planting severely reduce germination and sprouting rate. In corms, such as anemone and buttercup, de-vernalization can lead to a total arrest of meristem development. In lily, de-vernalization is linked with an increase in glycerol content in the bulb. Glycerol and/or its metabolites also induce the upregulation of genes linked to dormancy and to the down-regulation of flowering-promoting genes. In the context of climate changes and in view of the damaging interactions of higher temperatures with flowering-promoting pathways, it is important to further explore the regulation of de-vernalization in bulbs and corms.

Keywords: climate, flower induction, metabolites

O-19

Simulated spring freezes cause bud abortion and receptacle necrosis in Paeonia lactiflora ‘Festiva Maxima’

Nathan Jahnke, John M. Dole (john_dole@ncsu.edu), David Livingston III, Tan Tuong North Carolina State University, Raleigh, NC, USA

Sub-zero temperatures during spring freeze events can cause significant losses in North Carolina (NC) cut peony (Paeonia lactiflora Pall.) production fields. Damaged buds fail to open and internal necrosis is visible in the receptacle. Two protocols were developed to simulate spring freezes using data from three weather stations surrounding two of the largest NC cut peony producers. The cultivar Festiva Maxima was subjected to simulated spring freezes as potted plants at two growth stages prior to flowering where the minimum temperatures were either −3 or −6°C for 1 hr. Bud abortion was only observed on peonies at the second growth stage and the highest percentage of buds aborted when simulated freezes had a minimum temperature of −6°C. If freezing occurred, peony shoots always froze from the root system upwards, which was confirmed and visualized using an infrared camera. Some shoots at both growth stages 2 and 3 remained supercooled (the ability of water to remain below 0°C without ice nucleation) throughout both simulated freezes of −3 and −6°C. Histological sections of a necrotic receptacle depicted air pockets in the receptacle tissue characteristic of ice damage.

Keywords: cut flowers, perennials

O-20

Identification of below-ground phenotypic markers for early flowering (Cycle 1) Gladiolus hybridus: daughter corm and cormel production, cormel types

Neil O. Anderson (ander044@umn.edu) University of Minnesota, St. Paul, MN, USA

Gladiolus hybridus (Iridaceae) is an important herbaceous perennial and cut flower crop. As a geophyte, it produces corms and cormels for perennial survival and cloning. The life cycle of gladiolus (seed to flower) is typically 3–5 years, which slows the rate of breeding progress. We have developed rapid generation cycling (RGC) lines that flower in ≤ 1 year from sowing (Cycle 1). After the first year ends, it is impossible to phenotypically distinguish Cycle 1 RGCs from seedlings flowering in years 2–5 (Cycles 2–5) using above-ground traits. The objective of this study was to screen below-ground structures to determine if unique phenotypic traits(s) could be found for Cycle 1s. Two experiments were conducted (2021; 2022): Expt. 1 screened traits across Cycles 1–5 genotypes (n=1 clone/genotypes); Expt. 2 expanded replications/ genotype (n=5). Expt. 1 had n=140 genotypes (categories: 22-Cycle 1s; 3-cultivars, ‘Manhattan’, ‘Fordhook’, ‘White Prosperity’–potential Cycle 1s; 94-UMN cycles 2–5; 20-cvs. Cycles 2–5; 1-wild spp.) whereas Expt. 2 tested n=88 in categories: 18-Cycle 1s; 3-cultivars potential Cycle 1s, ‘Manhattan’, ‘Fordhook’, ‘White Prosperity’; 34-Cycle 2s; 34-Cycles 2–5, including wild spp.). Gladioli were field-grown and harvested post-flowering in late fall. Traits examined in Expt. 1 included: no. daughter corms, no. cormels/quadrant/corm, no. cormels, no. UCT (unbranched cormel type), no. BsCT (branched, simple cormel type), no. BfCT (branched, fasciated cormel type), cormel production/quadrant/corm. Cormel production/ quadrant/corm was not significantly different among cycle categories and was eliminated in Expt. 2. In both experiments, three below-ground traits were either significantly higher (no. daughter corms, unbranched cormel counts) or lower (no. of cormels/fasciation) for Cycle 1 genotypes than Cycles 2–5. All other traits overlapped among Cycles. These three traits can be used to distinguish Cycle 1 vs. Cycles 2–5, regardless of age. Future research will focus on identifying molecular markers linked with one or more of these traits.

Keywords: cormels, corms, geophyte, Gladiolus

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