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Zygotic embryo explants of grape cultivar AXR#1 were isolated from maw-e seeds and cultured on medium supplemented with naphthoxy acetic acid beta-(NOA) and benzylaminopurine (BA). Embryo explants dedifferentiated to form embryogenic callus. Globular stage embryos were visible in 9-10 months. On transfer 10 a growth regulator free medium supplemented with charcoal these globular embryos underwent further stages of embryo development. In a period of 30-40 days embryogenic tissues turned into clumps of somatic embryos displaying different stages of development Cotyledonary stage embryos were separated and transferred to basal medium. These embryos developed into complete plants. Cold and desiccation treatment of somatic embryos significantly enhanced the rate of plant conversion. Hypocotyl segments of elongated somatic embryos were good source explant for induction of shoot organogenesis. The hypocotyl-length and the proximity to-shoot-apex were found to influence the rate of shoot induction from hypotyl segments. Multiple shoot complexes which formed on hypocotyl segments were separated and individual shoots were grown on a root induction medium resulting in complete plant development. The possibility of both embryogenic and organogenic modes of plant regeneration make somatic embryos a highly versatile explant source for experiments on genetic manipulation.
Abstract
Episcia cupreata (Hook.) Hanst. ‘Pink Panther’ plants were drenched with 0, 0.07, or 0.21 mg a.i. paclobutrazol and given night interruption lighting (NIL) of 4 hr (2200-0200 hr) at 2.6 μmol·s−1·m−2 or no light interruption. Paclobutrazol and NIL did not affect days to first flowering, while flower numbers per plant increased exponentially over time on paclobutrazol-treated and control plants. NIL increased flowers per plant from day 47 on. Flower longevity was greater on paclobutrazol-treated plants than controls. Plant size (canopy radius) was reduced by paclobutrazol, which caused a greater flower density per canopy area. Chemical name used: (R*, R*)-(±) β-[(4-chlorophenyl)methyl]-α-(l,l-dimethylethyl)-1H-l,2,4-triazole-1-ethanol (paclobutrazol).
Ethylene is a known causal factor in the decay and senescence of fruits and vegetables. The aim of the present study was to incorporate a gene for control of ethylene biosynthesis in order to prevent or delay the senescence of the cauliflower curds. We first developed a reproducible transformation system using marker genes for beta glucuronidase (GUS) and antibiotic resistance. Brassica oleraceae L. var. botrytis was transformed by inoculating hypocotyl explants with the Agrobacterium tumefaciens strains C58 or EHA101 containing plasmids pAG5110, pAG5420, or pAG5520. The plasmid pAG5110 contains the genes for neomycin phosphotransferase II (NPTII) and GUS. The plasmids pAG5420 and pAG5520 contain a functional gene for S-adenosylmethionine hydrolase (SAMase) under an ethylene or wound inducible promoter, respectively. Hypocotyl explants were screened on regeneration medium with kanamycin for selection of transformants. Shoot regeneration occured within 4-6 weeks and morphologically normal plants developed within 3-4 months. The transgenic nature of the plants was confirmed by histochemical GUS assay, an ELISA based NPTII assay and Southern blot analysis. Transgenic plants outplanted in the greenhouse are being evaluated and selfed to study expression and inheritance pattern of the introduced trait.
Abstract
Leatherleaf fern [Rumohra adiantiformis (Forst.) Ching] was grown in controlled environment chambers set for day/night temperatures of 35/24C (high temperature regime, HTR) or 24/13C (low temperature regime, LTR). Fronds were harvested for vase life studies at 1100 and 1800 HR and held in holding rooms in deionized water. Plants were then moved to a greenhouse environment (16–25C) and, after 1 week, an additional set of fronds were harvested. Water uptake of harvested fronds declined exponentially and was generally lower for HTR fronds. HTR fronds had, for the most part, reduced vase life compared to LTR fronds. Most (81%) of the HTR fronds exhibited desiccation symptoms, whereas none of the LTR fronds did. These differences did not appear to be related to preharvest diffusive resistance or water potential differences.
Abstract
Twenty gerbera (Gerbera jamesonii H. Bolus, ex Hook f.) cultivars were evaluated for longevity in deionized water (DI), deionized water containing 1 mg fluoride (F)/liter, and deionized water containing 200 mg 8-hydroxyquinoline citrate (8-HQC) + 20 g sucrose (S)/liter. Flowers of different cultivars differed in fluoride sensitivity. Sensitive cultivars developed necrosis on the tips of ray florets within 12 to 24 hr of exposure to fluoridated water, whereas the least-sensitive cultivars were injured within 4 to 6 days. Petal necrosis was the prim ary factor reducing longevity in fluoridetreated flowers. Petal necrosis did not occur on flowers held in DI or 8-HQC + S. The mean postharvest lives of the 20 cultivars held in fluoridated water, DI, and 8-HQC + S were 2.6, 5.3, and 8.3 days, respectively.
Broccoli and cauliflower are among the most regeneratively intractable genotypes found in the brassicaceae. To develop a method for transfer of the gene encoding S-adenosylmethionine hydrolase (SAMase) into inbred broccoli and cauliflower germplasm, we investigated the morphogenic competence and Agrobacterium susceptibility of a wide range of tissues of varied source. Appropriately controlled expression of the SAMase gene should, theoretically, reduce the plant's capacity for ethylene biosynthesis and extend the post harvest shelf life of the flower head.
Through examination of the in vitro response of a wide range of tissues we identified procedures which support caulogenesis from 100% of explants, each producing more than 30 shoots which readily convert to plantlets. Studies with several wild type and disarmed Agrobacterium strains, and utilization of the binary vector system and appropriate marker and reporter genes, led to the identification of methods for high frequency T-DNA transfer to explant tissues and the flow frequency of transgenic plants containing SAMase gene.