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  • Author or Editor: Paul E. Read x
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The leaf reaction of the Phaseolus vulgaris L. germplasm—UNECA (M6 mutant derived from the cultivar Chimbolito, Costa Rica), `Chimbolito', BAC-6 (Brazil), XAN-159 (Centro Internacional de Agricultura Tropical, Cali, Colombia), and `PC-50' (Domican Republic)—to Xanthomonas campestris pv. phaseoli strain V4S1 (Dominican Republic) were determined in two replicated trials conducted in a greenhouse in Lincoln, Neb. (Feb.–Mar. and July–Aug. 1993). `PC-50' and `Chimbolito' were susceptible to Xcp strain V4S1 in both tests. UNECA, BAC-6, and XAN-159 had similar levels of resistance to Xcp in the July to August trial. However, in the February to March trial, the resistance of UNECA was greater than that of BAC-6 but less than that of XAN-159.

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Abstract

Shoot proliferation of lingonberry (Vaccinium vitis-idaea ssp. minus) was achieved in vitro from shoot tips excised from 1-year-old stock plants and cultured on a low-salt medium supplemented with 2iP. Rooting was obtained without auxin application by placing microshoots in a peat-vermiculite medium in a high humidity chamber. After 6 weeks, the rooted plantlets were transplanted into a peat-lite mix, subjected to a 2-week low humidity acclimation process and subsequently acclimated in a greenhouse under 50% shade. Within 9 months, these plantlets developed a rhizomatous growth habit, in contrast to the nonrhizomatous habit of conventionally rooted cuttings. Chemical names used: N-(3-methyl-2-butenyl)-1H-purin-6-amine (2iP).

Open Access

Shoot tips (7 to 10 mm long) of rosemary plant (Rosmarinus officinalis L. 'Lockwood de forest') were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations of thidiazuron (TDZ) (0, 0.5, 1.0, 1.5, and 2 mg/l) alone or with 3-indole acetic acid (IAA) at 0.5 mg/l. The effect of TDZ and IAA on the proliferation of rosemary shoot tips has been reported in a previous meeting. Here, we report on the effect of TDZ and IAA on the monoterpene constituents identified in the oil of rosemary plants propagated in vitro. The proliferated explants were soaked in hexane as a solvent, then the extractions were used for monoterpene analysis using GC/MS. A significant interaction of TDZ by IAA was found on most of the oil components identified. The highest levels of 1,8-cineole and borneol were obtained at 0.5 mg TDZ/l alone, while the highest level of camphor was obtained at 0.5 mg TDZ/l plus 0.5 mg IAA/l. The highest level of bornyl acetate was at 2 mg TDZ/l.

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The use of buffalograss [Buchloe dactyloides (Nutt.) Engelm] in home lawns and golf courses has been increasing because of its drought resistance and low growth habit. In vitro regeneration of buffalograss at a high frequency may provide an effective tool to introduce new variation for breeding use. The positive effects of AgNO3 on friable embryogenic callus production and regeneration efficiency is well documented in maize. In order to determine if AgNO3 has the same effect on buffalograss, two vegetatively propagated cultivars, a female `609' and a male `45-3' were tested at three different concentrations of AgNO3 at 5, 10, and 15 mg·L–1 using immature inflorescences as explants. Murashige and Skoog medium supplemented with 2 mg 2,4-D/L was employed as the control medium. Medium containing AgNO3 significantly promoted the production of friable callus for `45-3' with the highest percentage achieved at 10 mg AgNO3/L. AgNO3 medium led to production of significantly larger calli than found for the control. However, no difference was detected among 5, 10, and 15 mg AgNO3/L with regard to the callus formation ability and the size of callus initiated on these three treatments. Calli were then transferred to MS medium supplemented with BA at 0.1, 0.5 or 1.0 mg·L–1 to induce shoot formation. BA at 0.5 mg·L–1 gave the best differentiation response. Calli formed in the absence of AgNO3 produced more shoots per callus, but more calli were produced in the presence of AgNO3, and the overall regeneration efficiency was much higher with AgNO3 at 10 mg·L–1. In contrast, AgNO3 showed no promotive effect on callus production and regeneration for `609'.

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Few studies on embryogenesis in common bean (Phaseolus vulgaris L.) have been reported and only the early stages of somatic embryogenesis were observed. Dry seeds from two common bean lines were germinated in darkness on L-6 medium containing 4% sucrose, 0.2 g casein hydrolysate /liter and 2.0 g phytagel /liter. The medium for seed germination was supplemented with 0, 2, 4 or 6μM forchlorfenuron (CPPU). Explants from cotyledonary leaves, petioles, hypocotyls and shoot apices were prepared from 14 day-old seedlings. Callus was derived from explant cultures incubated in darkness at 26C on the medium containing 4 μM 2,4-D and 1 μM Kinetin. The callus was transferred after 4 weeks into 125 ml Erlenmeyer flasks containing 50 ml liquid medium and placed on a gyrotary shaker (120 rpm) under cool-white light (12 μmol.m-2 .s-1 ). The liquid medium was used with 2, 4 or 6 μM of 2,4-D alone or with zeatin supplements at relative concentrations of 0.25 and 0.5. Up to 200 somatic embryos from 40 to 50 mg callus inoculations were induced after 4 to 5 weeks. Callus derived from seedlings grown on CPPU-containing medium gave more repetitive somatic embryos. Cotyledonary stage embryos with clear bipolar structure were observed only from callus derived from seedlings grown on CPPU when transferred to suspension cultures containing 2,4-D and zeatin. All somatic embryos differentiated strong roots and some developed leaf-like structures on conversion medium.

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Callus of Rosmarinus officinalis L. 'Lockwood de forest' was induced from stem segments (3 mm long) using different concentrations of thidiazuron (TDZ). The original stem segments used as explants were found to have a higher level of linalool than was found for leaf segments. Linalool is one of the monoterpenes identified in rosemary plants and it has a pleasant aroma. TDZ has a significant effect on callus formation and callus texture. The callus formed was light green to yellow and/or had some meristimatic dark green cells. TDZ had a significant linear effect on the callus fresh weight. The meristimatic green cells formed on all calli except those proliferated on the lowest concentration of TDZ (0.5 mg/l). No callus was induced from stem segments cultured on TDZ-free medium. The fresh calli from other treatments were soaked in hexane as a solvent for monoterpene analysis using GC/MS. No monoterpenes could be detected in the callus induced on the medium containing the lowest concentration of TDZ. Comparing to the stem segments taken from the parent plants only 4 of 10 monoterpenes identified were found in the callus: α-pinene, β-pinene, 1,8-cineole, and camphor.

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Abstract

Ethylene (C2H4) and CO2 levels and callus formation were influenced by photoperiods (8 hours-SD; 16 hours-LD) under which ‘Nita’ dahlia stock plants were grown and leaf segments incubated in vitro. Larger callus and higher levels of C2H4 and CO2 were detected when tissues from stock plants under SD were incubated under SD (SD-SD) than when incubated under LD (SD-LD). Tissue under LD-LD or LD-SD formed similar amounts of callus to SD-LD cultures, but C2H4 and CO2 levels were higher. Compared to water-sprayed controls, 2500 mg/liter butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide) sprayed on SD stock plants one day before explant removal promoted callus formation, and C2H4 and CO2 production in tissue incubated under either SD or LD. Daminozide sprayed on LD stock plants had no influence on callus or C2H4, but CO2 was increased under SD or LD incubation.

Open Access

Abstract

Encapsulated 2-chloroethyl-trimethylammonium chloride (chlormequat) stimulated and retarded growth of tomatoes, petunias, snapdragons, and mar-igolds. Low rates (3-6 g of 1, 2 oi 4% active ingredients/liter of growing medium) stimulated earlier bloom up to 14 days in these crops and doubled stem diameter in tomato. Conversely, higher levels of encapsulated chlormequat (12-25 g/liter) retarded plant height to 50% of controls and produced stocky more symmetrical bedding plants without deleterious effects.

Open Access

Rosemary (Rosmarinus officinalis) belongs to the Lamiaceae family, and is native to the Mediterranean and one of the most important medicinal herbs containing antioxidants in its leaves. One of the most important antioxidants is rosmarinic acid (RA). The aim of this study was to test the concentration of (RA) and chlorophyll content in leaves and callus of five successive subcultures of five different genotypes of rosemary. They were: 1) `Majorca'; 2) Rosmarinusofficinalis; 3) `Pine Scented'; 4) `Madeline Hill', and 5) APR. It was found that the highest concentration of RA in leaves was in `Pine Scented', while the lowest concentration was for APR and `Madeline Hill'. However, in the callus the highest RA concentration was for Rosmarinusofficinalis in the second subculture and `Madeline Hill' in the third subculture, while the lowest RA concentration was for `Majorca', `Pine Scented', and APR. The RA concentration in callus declined after the second and the third subculture for Rosmarinusofficinalis and `Madeline Hill', respectively. We concluded that it is preferred to use `Pine Scented' for RA extraction from the leaves while for RA extraction from callus it is better to use Rosmarinusofficinalis in the second subculture or `Madeline Hill' in the third subculture.

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The American Chestnut Foundation (ACF) has conducted a breeding program aimed at developing blight-resistant chestnut trees exhibiting the phenotype of American Chestnut [Castanea dentata (Marsh) Borkh]. Because such plants are difficult to propagate, we developed a protocol for in vitro multiplication of candidate blight-resistant plants resulting from the ACF breeding programs. Dormant shoots were taken from 5- to 8-year-old trees and forced, producing softwood growth for use as a source of explants for shoot multiplication. Best shoot proliferation took place on WPM containing 0.2 mg BA/L. Explant material for the rooting experiments was taken from 6- to 12-month-old proliferating cultures. The basal rooting medium consisted of WPM containing 0.01 mg IBA/L and was overlaid with a thin opaque layer. Rooting was enhanced overall with this bilayer approach. A “D/W” medium (DKW and WPM) was also used as a rooting medium containing 0.01 mg IBA/L and 0.2 mg BA/L, which further enhanced leaf quality and rooting for some genotypes. After several transfers on the bilayer system, explant growth appeared to become less juvenile in stem and leaf development and more analogous to mature later-season growth. The rooting responses and the time for rooting to be induced were highly variable among the different genotypes.

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