Search Results

You are looking at 71 - 80 of 1,152 items for :

  • "regeneration" x
  • Refine by Access: All x
Clear All
Free access

Richard L. Bell

Preconditioning effects of cytokinin in the shoot proliferation medium on explant quality and subsequent adventitious regeneration of `Bartlett' and `Beurre Bosc' pear were investigated. The basal medium for regeneration consisted of half-strength MS macro- and micronutrients, MS organics, 30 g·liter–1 sucrose, 6 g·liter–1 agar, and 10 μM thidiazuron (TDZ), and 1 μM NAA. Leaves from BAP medium were more effective than those from media with 2-iP or kinetin in spite of the increased leaf size of shoots cultured with 2-iP (28% vs. 10%). Use of leaves from in vitro-rooted shoots did not increase regeneration frequency (19.5% vs. 31%) of `Bartlett'. Actively expanding leaves are more suitable explants than larger, fully expanded leaves. Liquid medium overlays and incubation in liquid medium decreased regeneration frequency when compared with agar-solidified medium. Among auxins in regeneration induction phase media, IBA (0.5 or 1.0 μM) resulted in greater regeneration than NAA.

Free access

Jane Kahia, Margaret Kirika, Hudson Lubabali, and Sinclair Mantell

much attention. This is although DSE is preferred, as it has the potential for maintaining genomic stability of regenerated plants. The former method that is via an intermediate callus phase increases the possibility of somaclonal variations ( Tang and

Free access

Samir C. Debnath

The growth and development of lingonberry (Vaccinium vitis-idaea L.) plants propagated either by conventional softwood cuttings or by in vitro shoot proliferation from nodal explants and by shoot regeneration from excised leaves of micropropagated shoots, were studied in cultivars `Regal', `Splendor', and `Erntedank'. Significant differences were observed between the treatments. After 3 years of growth, the in vitro-derived plants produced more stems, leaves, and rhizomes than the conventional cuttings which rarely produced rhizomes. In vitro culture on nutrient medium apparently induces the juvenile branching characteristics that favor rhizome production. This increase in vegetative growth and rhizome yield of in vitro-derived plants over stem cuttings varied among genotypes.

Free access

Mark H. Brand

To introduce desirable trait genes into Kalmia latifolia, efficient adventitious shoot regeneration methods are needed. Silver Dollar (S$) callus induction and growth in the dark was compared on Woody Plant (WP) medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) (1, 5, 10, 20 μM) or naphthaleneacetic acid (NAA) (1, 10, 20, 40 μM) with and without 5 μM isopentenyladenine (2iP). Both 2,4-D and NAA produced >450 mg of callus from leaf explants in 8 weeks. The addition of 2iP tripled growth for 2,4-D and doubled growth for NAA. Greatest callus growth was obtained on 20-40 μM NAA or 5-20 μM 2,4-D. Shoot regeneration on callus was achieved on WP medium containing 30 μM 2iP or 1 μM thidiazuron (TDZ), but a combination of the two was best, with 68% of dark-grown calli regenerating shoots in 4 weeks. 26% more dark-grown calli regenerated shoots than light-grown calli. The type of auxin (2,4-D or NAA) used to grow the calli did not affect shoot regeneration. For direct shoot regeneration, S$ leaf explants were tested on WP medium containing 5, 15, 30, 45 and 60 μM 2iP. The addition of 1 μM indole-3-butyric acid (IBA) doubled the percentage of leaves that regenerated shoots. 2iP concentrations between 15 and 45 μM supported excellent shoot regeneration, but optimal regeneration (95% of explants, 5.1 shoots/leaf) occurred on 30 μM 2iP+1 μM IBA. Leaf explants of six cultivars were grown on optimal medium with shoot regeneration ranging from 17% to 93% of leaves and 1.8 to 8.2 shoots per leaf, depending on the cultivar.

Free access

John R. Stommel and Stephen L. Sinden

Cultured leaf explants obtained from 36 accessions of the wild tomato species, Lycopersicon hirsutum Humb. and Bonpl., were evaluated for morphogenic capacity in response to three cytokinins (zeatin, BA, and kinetin) in combination with IAA. Media containing 0.1 μm IAA plus 4.6 or 9.2 μm zeatin were optimal for shoot induction. Cotyledon explants were superior to true leaf explants for obtaining shoot formation. Morphogenic responses of L. hirsutum f. typicum and L. hirsutum f. glabratum were clearly accession-dependent and ranged from exceptional with numerous shoots produced to recalcitrant with no shoots produced. The high morphogenetic capacity of leaf explants from L. hirsutum f. typicum accession 128644 was also evident in protoplast-derived calli that readily regenerated shoots. Chemical names used (E)-2-methyl-4-(1H-purin-6-ylamino)-2-buten-1-ol (zeatin), N-(phenylmethyl) -1H-purin-6-amine (BA), N- (2-furanylmethyl) -1H- purin-6-amine (kinetin), 1H- indole-3-acetic acid (IAA).

Free access

J. L. Jacobs and C. T. Stephens

Several growth hormone combinations and silver nitrate concentrations were examined for their effect on regeneration of different pepper genotypes. Primary leaf explants from in vitro seedlings were cultured on a revised Murashige and Skoog medium supplemented with auxin, cytokinin and 1.6% glucose. Combinations of different concentrations of indole-3-acetic acid (IAA), 0-5 mg/l, and 6-benzylaminopurine (BAP), 0-5 mg/l, were tested to determine the most effective medium for shoot primordium formation. Experiments with IAA and BAP did not result in a specific growth hormone combination appropriate for regeneration of all genotypes tested. Of the silver nitrate concentrations tested, 10 mg/l resulted in the best shoot and leaf differentiation and reduced callus formation. Differences in organogenic response of individual genotypes were evaluated on a single regeneration medium. Whole plants were regenerated from 11 of 63 genotypes examined. Based on these experiments, a reproducible regeneration system for pepper was developed with a total of 500 plants regenerated to date.

Free access

J. L. Jacobs and C. T. Stephens

Several growth hormone combinations and silver nitrate concentrations were examined for their effect on regeneration of different pepper genotypes. Primary leaf explants from in vitro seedlings were cultured on a revised Murashige and Skoog medium supplemented with auxin, cytokinin and 1.6% glucose. Combinations of different concentrations of indole-3-acetic acid (IAA), 0-5 mg/l, and 6-benzylaminopurine (BAP), 0-5 mg/l, were tested to determine the most effective medium for shoot primordium formation. Experiments with IAA and BAP did not result in a specific growth hormone combination appropriate for regeneration of all genotypes tested. Of the silver nitrate concentrations tested, 10 mg/l resulted in the best shoot and leaf differentiation and reduced callus formation. Differences in organogenic response of individual genotypes were evaluated on a single regeneration medium. Whole plants were regenerated from 11 of 63 genotypes examined. Based on these experiments, a reproducible regeneration system for pepper was developed with a total of 500 plants regenerated to date.

Free access

Rengong Meng, Tony H.H. Chen, and Chad E. Finn

`Marion' is the most important blackberry cultivar in the world, primarily due to its outstanding processing characteristics. Ideally, `Marion' could be enhanced via transformation while maintaining its fruit quality. As a successful in vitro regeneration is the prerequisite for genetic transformation, a series of experiments were conducted to optimize the conditions for in vitro regeneration for `Marion' blackberry. Parameters studied included types (three cytokinins: BA, kinetin, and zeatin; four auxins: IBA, IAA, NAA, and 2,4-D) and concentrations of plant growth regulators, explants (leaf and petiole), medium formulations (MS, WPM, and BMM), and the duration of TDZ pretreatment (3 to 6 weeks) of in vitro-grown stock plants. The highest shoot regeneration rate (65.7%) and highest number of shoots (5.1 shoots/explant) were obtained under the following conditions: stock plants were pretreated with TDZ (1 mm) for 3 weeks, followed by leaf explants dark pretreatment for 1 week on the regeneration medium (WPM with 5 mM BA and 0. 5 mm IBA). After dark treatment, regeneration plates were placed under 16-h photoperiod at light intensity of ≈50 μmol·m-2·s-1 at 23 + 2 °C for 4 weeks.

Free access

D.J. Gray, D.W. McColley, and Michael E. Compton

A protocol for high-frequency somatic embryogenesis in Cucumis melo L. was developed using `Male Sterile A147 as a model cultivar. Basal halves of quiescent seed cotyledons were cultured on embryo induction (EI) medium containing concentration ranges of the auxin 2,4-D and the cytokinins BA, Bin, TDZ, or 2iP before transfer to embryo development (ED) medium. Medium with 2,4-D at 5 mg·liter-1 and TDZ at 0.1 mg·liter-1 was superior, with 49% of explants responding and an average of 3.3 somatic embryos per explant (6.8 somatic embryos per responding explant). More explants produced embryos when incubated on EI medium for 1 or 2 weeks (30% and 33%) than for 3 or 4 weeks or with no induction. However, 2 weeks was 2.9 times better than 1 week in terms of number of embryos per explant. One week of initial culture in darkness, followed by a 16 hour light/8 hour dark photoperiod, produced more responding explants (26%) than two or more weeks in darkness or no dark period at all; but 1 and 2 weeks of darkness resulted in a similar number of embryos per explant (2.1 and 2.8). Sucrose concentration in EI and ED media had a highly significant effect on embryo induction and development. EI medium with 3% sucrose resulted in more embryogenic explants than EI medium with 1.5% or 6% sucrose. However, treatments with 3% sucrose in EI medium and 3% or 6% sucrose in ED medium produced significantly more embryos per explant (8.5 and 11.9) than other treatments. Treatments did not affect embryo induction directly and regeneration per se but, instead, frequency and efficiency of somatic embryo development. The optimal treatments were tested with 51 other commercial varieties. All varieties underwent somatic embryogenesis, exhibiting a response of 5% to 100% explant response and 0.1-20.2 embryos per explant. Chemical names used: N-(phenylmethyl)-lH-purin-6-amine (benzyladenine or BA); N-(2-furanylmethyl)-lH-purin-6-amine (kinetin or BIN); N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron or TDZ); N-(3-methyl-2-butenyl)-lH-purin-6-amine (2iP); (2,4-dichlorophenoxy) acetic acid (2,4-D).

Free access

Jing-Tian Ling and Roger J. Sauve

Leaf segments of greenhouse-grown Ulmus americana L. plants cultured on a Murashige and Skoog basal salts medium supplemented with 0.22 mg/L thidiazuron formed friable type of callus and regenerated shoots. This friable callus readily formed a cell suspension when the callus was placed in a liquid MS medium containing 2 mg/L 1-naphthaleneacetic acid and 1 mg/L 6-benzylaminopurine. Shoots were regenerated from 3-month-old suspension cell cultures after the suspension cells had been cultured on solid medium. Shoots developed roots on MS medium containing 0.1 mg/L indole-3-butyric acid. Intact plants were successfully established in soil.