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Kullanart Obsuwan, Wayne B. Borth, John Hu, and Adelheid R. Kuehnle

A Cymbidium mosaic virus movement protein gene with a site-specific mutation (mut11) under control of a ubiquitin promoter was inserted using biolistics into two Dendrobium varieties with the intention of creating CymMV-resistant orchids. Presence of the transgene in regenerated plants of D. × Jaquelyn Thomas `Uniwai Mist' and D. x Jaq–Hawaii `Uniwai Pearl' was confirmed by PCR using genomic DNA, and mut11-positive plants were potted ex vitro. Forty-two transgenic plants and four non-transgenic control plants at the 4- to 6-leaf stage were inoculated with a 1:1000 dilution of CymMV obtained from infected orchids. Plants were analyzed for systemic infection using tissue blot immunoassay (TBIA). Seventeen plants from at least six independent transformations remained virus-free, whereas all control plants were infected with CymMV within 1 month. Further analysis by RT-PCR showed that the mut-11 mRNA was detectable in only two of these 17 plants. All plants were challenged again with a second CymMV inoculation as above, followed by TBIA analysis after 1 month. Thirteen of 17 plants remained free from virus. A third challenge of these plants with CymMV as above was followed by TBIA analysis at 1 week, 2 weeks, 1 month, 3 months, 6 months, and 12 months after challenge. Results at 2 weeks post-inoculation showed that all six controls and four individual transgenic plants, including the RT-PCR-positive plants, became systemically infected. Nine transgenic plants from both varieties remained free from CymMV 12 months after the third challenge. Lack of detectable mut11 mRNA in these resistant lines suggests that a post-transcriptional gene silencing (PTGS) mechanism may be conferring resistance to CymMV.

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Jen-An Lin and Yao-Chien Alex Chang

Phalaenopsis (the moth orchid) is currently the most important indoor potted flowering plant worldwide ( Royal Flora Holland, 2017 ; U.S. Department of Agriculture, 2016 ). Growers normally produce phalaenopsis at high temperatures (>28 °C) to

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Katrina G. Porter and Adelheid R. Kuehnle

advertisement solely to indicate this fact. 1 To whom reprint requests should be addressed. This research was funded by grants from the Gloeckner Foundation, the Dendrobium Orchid Growers' Association of Hawaii, and the Big Island Dendrobium Growers

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Ernie DeMarie, Molly Weimer, and K.W. Mudge

Green pods of the C. reginae orchid were collected from a bog near Ithaca, NY. Pods were surface sterilized, and seeds were plated on agar media. The 8 germination treatments were arrange in a complete 3 way factorial consisting of 2 basal media (fish emulsion, FE vs. yeast extract, YE), 2 media pHs (4.8, 6.8), and 2 temperature regimes (constant 24 C vs. 6 wks. at 5 C prior to transfer to 24 C). Sequential stages of development included embryo enlargement and rupture of the testa (l), root elongation (2), leaf primordium development (3) and finally rhizoid development with or without protocorm greening (4). After 4 months post sowing, germination (stage 1 or beyond) was 56% and 0% on FE at pH 4.8 and 6.8 respectively, and 45% and 78% on YE at pH 4.8 and 6.8 respectively. Protocorm development from unchilled seeds after 4 months was greatest on YE at the lower pH, with 14% reaching stage 3 or 4, as contrasted to only 5% reaching stage 2 (none beyond), for the other germinated treatments. Chilled seeds had higher germination for all treatments but no development beyond stage 1 at 4 months post sowing.

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Hongmei Ma, Margaret Pooler, and Robert Griesbach

the wild-type phenotype with solid purple petals, sepals, and labellum. All plants were grown in commercial orchid greenhouses until flowering. Flowering plants were then held in the laboratory for the duration of the study. The flower buds of P

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Christine Yung-Ting Yen, Terri W. Starman, Yin-Tung Wang, and Genhua Niu

Dendrobium was reported to be the second most valued orchid genus in Japan in 2002 with a market share of 20%, only behind Phalaenopsis with a 30% market share ( Laws, 2004 ; Wang, 2004 ). Dendrobium has been the most economically

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Mou Zong-min, Yan Ning, Li Shu-yun, and Hu Hong

plant physiological characteristics, e.g., high-quality flowers and vigorous seeds, which are valuable in horticulture and seedling production, respectively. For ornamental orchids, N fertilization can help growers produce orchids more efficiently. The

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Yin-Tung Wang

An experiment was initiated to determine the effect of a low N, high P and K fertilizer applied during the flowering season on a hybrid moth orchid (Phalaenopsis TAM Butterfly Blume.). On 1 Sept., plants of flowering size receiving N, P, and K at 100, 44, and 83 mg·L–1, respectively, from a 20N–8.8P–16.6K soluble fertilizer were given N, P, and K, at 30, 398, and 506 mg·L–1 (high P), respectively, at each or every fourth irrigation. Control plants continued to receive the 20N–8.8P–16.6K fertilizer. The high P treatments, regardless of the frequency of application, had no effect on the date of emergence of the flowering stem (spiking), anthesis, or flower size. All plants treated with the high P fertilizer had fewer flowers (15 to 19) than the controls (24 flowers). Continuous application of adequate N appears to be more important than low N and increased P for optimal flowering. In a separate experiment using the same hybrid orchid, terminating fertilization completely on 1 Sept., 29 Sept., or 27 Oct. or when the flowering stems were emerging (1 Oct.) reduced flower count (≤19 vs. 24). Flower longevity was reduced by 12 d when fertilization was terminated on 1 Sept. Flower size was unaffected by any treatment in either experiment. Discontinuing fertilization prior to late November reduced flower count. Withholding fertilization for extended periods resulted in red leaves, loss of the lower leaves, and limited production of new leaves.

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Hongmei Ma, Margaret Pooler, and Robert Griesbach

P. schilleriana Rchb. were used in this study. All plants were grown in commercial orchid greenhouses until flowering. Flowering plants were then held in the laboratory for the duration of the study. Gene constructs. Promoters, structural

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Ken W. Leonhardt