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  • Author or Editor: R. H. Zimmerman x
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`McIntosh' apple shoots were inoculated in vitro with Agrobacterium tumefaciens strain tms328::Tn5 (tms) carrying a functional cytokinin gene. Callus tissue, removed from the infected stems, produced shoots on shoot proliferation medium. After three subcultures, axillary shoot production from a tms-infected putative transformant was eight times that of controls. Subsequent shoot production on three different levels of BA (3, 6 and 10 uM) was significantly greater than from controls on all levels of BA. PCR analysis of putative transformants revealed an expected 503 bp DNA fragment corresponding to the amplified portion of the cytokinin gene. After 6 months of in vitro propagation, proliferation rates of shoots obtained from the original transformants were similar to the controls and the expected PCR fragment of 503 bp could only be detected by Southern analysis. Even though the T-DNA appears to be lost from the apple genome, the data suggest that the tms strain may be useful in co-infection experiments to induce shoot formation, thus avoiding difficult regeneration procedures.

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Abstract

Thornless blackberries (Rubus sp.) were propagated throughout the year by rooting leafy 1-node cuttings. Differences in ease of rooting among cultivars were evident with ‘Smoothstem’ generally being the most difficult and ‘Black Satin’, SI-US 68-6-6, and SI-US 68-6-17 being the easiest to root. Treatment with 0.3% indolebutyric acid in talc sometimes improved rooting slightly. Although more and longer roots developed when sand was the rooting medium, roots were brittle and broke off easily when the cuttings were handled. Cuttings rooted nearly as well in 1 peat: 1 perlite mix, had a more fibrous root system, and were easier to handle in transplanting. Rooting was as successful under a plastic tent as under intermittent mist. Node location along the cane did not influence rooting of the cuttings as long as the succulent tissue at the stem tip was not used.

Open Access

Abstract

In the article “Gelling Agent and Growth Regulator Effects on Shoot Vitrification of ‘Gala’ Apple in Vitro”, by P.-L. Pasqualetto, R.H. Zimmerman, and I. Fordham (J. Amer. Soc. Hort. Sci. 111:976–980, November 1986), two corrections should be noted: 1) On p. 979, the 11th line in the discussion, Fig. 1 should read Fig. 2. 2) The correct version of Table 1 is printed below.

Open Access

Abstract

Shoot tips of ‘Gala’ apple (Malus domestica Borkh.) were grown on proliferation medium containing Murashige and Skoog salts, supplemented with 0.56 mm myo-inositol; 1.2 μm thiamine-HCl; 2.2 or 4.4 μm BA; 0.005, 0.05, or 0.5 μm IBA; and 1.3 μm GA3. The media were solidified with Gelrite at concentrations from 0.5 to 1.5 g·liter−1 plus agar (Sigma) from 0.5 to 4.0 g·liter−1. Vitrification was influenced both by gelling agent and BA concentration, whereas the IBA concentration had little effect. Increasing either agar or Gelrite concentration resulted in a decreasing percentage of vitrified explants. The higher BA level generally increased vitrification, but increasing the agar concentration tended to reduce the difference in effect of the 2 BA levels. Certain combinations of gelling agents produced no vitrification with no reduction in shoot proliferation, and with a clarity of the medium approaching that of Gelrite alone. Chemical names used: N-(phenylmethyl)-lH-purin-6-amine [benzyladenine (BA)]; lH-indole-3-butanoic acid (IBA); and gibberellic acid (GA3).

Open Access

In vitro-grown shoots of `Doyenne d'Hiver' pear (Pyrus communis L.) were maintained for 7 days on 16-h photoperiods at photosynthetic photon fluxes (PPF) of 90, 180 or 270 μmol·m-2·s-1 and irradiated 6 h per day midway through the photoperiod at 0.2 (-UV-B) or 12.0 (+UV-B) kJ·m-2·d-1 of biologically effective ultraviolet-B (UV-BBE) radiation. Increased ethylene production from UV-BBE-treated shoots as compared to the control was recorded after 24 h in cultures grown under 90 and 180 μmol·m-2·s-1 and after 72 h in shoots grown under 270 μmol·m-2·s-1; PPF level had little effect on amount of ethylene evolved. Proliferation was highest at 270 μmol·m-2·s-1, but UV-BBE decreased proliferation and increased apical necrosis. UV-BBE treatment increased lipid peroxidation after 24 h based on malondialdehyde (MDA) determination, but thereafter had no consistent effect on MDA. UV-BBE exposure slightly decreased the monogalactosyldiacylglycerol/digalactosyldiacylglycerol ratio during the initial 24 h, showing an effect on chloroplast membranes.

Free access

RAPD analysis was performed on 44 species of Rubus. These species included representatives from seven of the 12 subgenera within the genus and several series within the Idaeobatus (raspberries) and Eubatus (blackberries) subgenera. For all species, up to five plants were initially analyzed by two 10-mer primers. The most heterozygous of these individuals was then analyzed using 13 additional primers. Wide band diversity exists among Rubus species; these differences were analyzed using the PHYLIP software program. These differences are repeatable, for example color sports of `Heritage' red raspberry produced identical banding patterns. The genetic similarity between eastern United States blackberries (Eubatus) and numerous species was compared to the ability of these same species to act as a suitable pollen parent for eastern blackberries. These data were used to construct a dendrogram of the subgenera studied here.

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Autumn olive (Elaeagnus umbellata Thunb.) has edible fruit with brilliant red or yellow pigmentation. An analysis of the pigment in fruit of five cultivars and six naturalized plants showed that the berries contain lycopene, α-cryptoxanthin, β-cryptoxanthin, β-carotene, lutein, phytoene, and phytofluene. The lycopene content per 100 g ranged from 15 to 54 mg in fresh fruit from the naturalized plants and from 17 to 48 mg in the four cultivars with red-pigmented fruit. A cultivar with yellow fruit had only 0.47 mg/100 g fresh fruit. In contrast, fresh tomato fruit, the major dietary source of lycopene, has a lycopene content per 100 g of ≈3 mg. This newly identified source of lycopene may provide an alternative to tomato as a dietary source of lycopene and related carotenoids.

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Shoot regeneration from apple (Malus domestica Borkh.) leaf explants following particle bombardment at various acceleration pressures was studied. Basal leaf segments of micropropagated `Royal Gala' apple were bombarded with 1 μm gold particles, accelerated using helium pressures of 4.5, 6.2, 7.6, 9.3, or 13.8 MPa (650–2000 psi), and cultured on shoot regeneration medium consisting of N6 salts supplemented with 10 μM TDZ for 5, 10, or 20 days in darkness. Bombarded and control explants exhibited 63% to 100% shoot regeneration. With a 5-day dark period, average shoot production per explant ranged from 6.1 to 14; bombardments of 4.5 and 6.2 MPa significantly increased shoot production over the controls. With a 10-day dark period, average shoot production per explant ranged from 9.1 to 22 following bombardment at 9.3 and 6.2 MPa, respectively. Following bombardment at 6.2 MPa, 75% of the explants produced more than 20 regenerants per explant. With a 20-day dark period, average shoot production per explant ranged from 8.9 to 19 following bombardment at 13.8 MPa and following no bombardment, respectively. Shoot production per explant was significantly less than the controls following bombardments ranging from 6.2 to 13.8 MPa. Shoot production was highest per explant with particle bombardment at 6.2 MPa followed by incubation in darkness for 10 days. Chemical name used: thidiazuron (TDZ).

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Particle bombardment has been shown to be useful for genetic manipulation of many plants; however, a critical component for successful transformation is the ability of transformed cells to regenerate plants. This study describes factors that affect the regeneration efficiency of apple leaf explants following particle bombardment. Basal leaf segments of micropropagated `Royal Gala' apple were treated with 1μm gold particles (0.5 μg/10μl), accelerated at either 4.5, 6.2, 7.6, 9.3 or 13.8 MPa, and cultured on N6 salts + l0μM TDZ regeneration medium for 5, 10 or 20 days in the dark. Both microprojectile-treated and control explants exhibited 85-100% regeneration. However, only 30-60% of the explants bombarded at 7.6, 9.3 and 13.8 MPa had more than 10 regenerants and 6-10% had more than 20 regenerants, whereas for control explants and those bombarded at 4.5 and 6.2 MPa, 70-90% had more than 10 regenerants and 30-50% had more than 20.

Free access

Abstract

No consistent trend towards increased inbreeding has existed within the U.S. Department of Agriculture pear breeding program over 17 years of crosses based on the mean inbreeding coefficient and the percentage of non-inbred progenies. Selections did not tend to be more or less inbred than the population of all seedings. There was consistent, but small, trend towards a reduction in seedling vigor with increased levels of inbreeding as measured by 5th year stem diameter. A significant positive, but small, association between increased inbreeding and improved flavor, grit, and texture were observed, even after correction for the effects of parental values for these characters. Limited inbreeding does not adversely affect improvement of fruit quality and appears to be of some benefit in facilitating selection of favorable alleles.

Open Access