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Michael Marcotrigiano

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Michael Marcotrigiano

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Michael Marcotrigiano and Grant Hackett

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Michael Marcotrigiano and Susan P. McGlew

A teaching exercise that rapidly and inexpensively demonstrates the effects of leaf reduction on the rooting of stem cuttings is described. Coleus stem cuttings with whole leaves, half leaves, or no leaves are placed in sand on either misted or nonmisted greenhouse benches. Rooting response is recorded by ranking root systems by comparison to a diagram. A demonstration is also described that uses leafless cuttings cultured in vitro on solidified media containing a carbohydrate and/or auxin source. This demonstration gives students information that will help them speculate on the physiological reasons for the poor rooting response of leafless herbaceous cuttings.

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Michael Marcotrigiano and Susan P. McGlew

In an effort to accelerate breeding programs and to study somaclonal variation, a micropropagation system was devised for cranberries (Vaccinium macrocarpon). Using a factorial design, explants taken from greenhouse grown plants were placed on Anderson's medium containing different concentrations of 2ip' GA3, and IBA, with 4 cultivars tested over 3 subcultures. In other experiments, explant source, macro and micro salt formulations, and rooting treatments, were studied. Optimal multiplication and shoot quality occurred when single node explants taken from greenhouse grown plants were placed on Anderson's media containing 150 uM 2iP, 1.0 uM IBA and no GA3. Histological examinations indicate that initial response is axillary bud proliferation but upon subculture adventitious shoot formation may be possible. Proliferated shoots could be rooted ex vitro in plug trays under plastic tents and without hormone treatments. Optimal rooting occurred under high light conditions in a 1:1 (v:v) peat:sand mix. Plants were easily transplanted into the field in spring and will be evaluated by comparison to conventionally propagated material.

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Michael Marcotrigiano and Susan P. McGlew

A two-stage micropropagation system was devised for cranberries (Vaccinium macrocarpon Ait.). Shoot-tip explants taken from four cultivars of greenhouse-grown plants were placed on media composed of Anderson's major salts, Murashige and Skoog's (MS) minor salts and organics, plus various concentrations of 2iP, IBA, and GA3. In other experiments, explant source, salt formulations for media, and rooting treatments were studied. Optimal multiplication and shoot quality occurred when nodal explants taken from greenhouse-grown or micropropagated plants were placed on medium containing 150 μm 2iP, 1.0 μm IBA, and no GA3. Histological examination revealed that the initial response of nodes to culture is axillary bud proliferation, but adventitious shoot formation occurred after 4 to 6 weeks. Cultures that contained only axillary shoots were not evident unless low levels of 2iP were used, at which point only axillary buds present on the explants were released. Proliferated shoots could be rooted ex vitro without auxin treatment. Optimal rooting occurred under high-light conditions. Plants were transplanted to the field for comparison to conventionally propagated material. Chemical names used: gibberellic acid (GA3), N-(3-methyl-2-butenyl)-1H-purin-6-amine (2iP), 1H-indole-3-butanoic acid (IBA).

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Bindu Chawla, Robert Bernatzki, and Michael Marcotrigiano

Lycopersicon peruvianum is a wild species of tomato that exhibits gametophytic self-incompatibility (S), wherein the SI response is controlled by the genotype of the pollen. Cultivated tomato (L. esculentum) is a self-compatible species. Assisted by phenotypic markers, periclinal graft chimeras between these two species have been obtained. Fruit set analysis following breeding demonstrated that the available five chimeras (PPE, PEE, PEP, EPP, and EEP) are able to accept pollen from L. peruvianum, suggesting that there is a failure of the SI response. SI response is known to be dependent on S-locus associated proteins. These proteins are present in the style, which is mainly derived from the L1 and L2 layers of meristem. RNA analysis of the style tissue using a cloned S-locus cDNA as a probe showed that, except for EEP, all chimeras expressed the S-allele. This was also confirmed by SDS-PAGE analysis of stylar proteins that were present in variable amounts depending on the periclinal combination. Thus, the breakdown of SI is not associated with the lack of expression of the S-locus. Further work is being conducted to understand the nature of this breakdown.

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Thomas H. Boyle, Michael Marcotrigiano, and Suzanne M. Hamlin

Investigations were performed to determine the influence of gibberellic acid (GA3) on intact plants and cultured phylloclades of `Crimson Giant' Easter cactus [Rhipsalidopsis gaertneri (Regel) Moran]. Responses of intact plants depended on GA3 concentration, number of spray applications, and application time. Single GA3 applications delayed flowering and reduced the percentage of apical phylloclades flowering and number of flower buds per plant when applied before floral primordia formation [from 20 days before to the start of long days (LDs)], but hastened flowering and did not affect the percentage of apical phylloclades flowering or number of flower buds per plant when applied during floral bud development (20 days after the start of LDs). When sprays were applied at or before the start of LDs, increasing the GA, concentration resulted in fewer plants flowering, longer flowering delays, and further decreases in the number of flower buds per plant. Multiple GA3 applications were more inhibitory to flowering than single applications. Whole plants and cultured phylloclades exhibited similar reactions to GA3, but cultured phylloclades were more responsive to GA3 than intact plants. Intact plants and cultured phylloclades generally produced more new phylloclades as GA3 concentration increased. Spine growth also increased when phylloclades were cultured in a GA3-containing medium. Flowering was accelerated by ≈55 days when GA, was applied to intact plants with 1- to 2-mm-long flower buds. GA, may be horticulturally useful for Easter cactus crop scheduling.

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Michael Marcotrigiano, Thomas H. Boyle, Pamela A. Morgan, and Karen L. Ambach

Nuclear-controlled leaf variegation was studied among Coleus × hybridus Voss (formerly C. blumei Benth.) cultivars propagated by seed and as shoot cultures on Murashige and Skoog (MS) medium + 1 to 3 mg BA/liter. Cultivars tested possessed pattern chlorophyll variegation and either pattern or nonpattern anthocyanin variegation. The gene controlling an albino midrib region appears to be fairly stable, with only 2% of the micropropagated plantlets having a solid-green leaf characteristic, a characteristic that was always inherited following selfing. Pattern anthocyanin variegation (PAV) was fairly stable, while nonpattern anthocyanin variegation (NAV) was very unstable. In addition, variants from pattern-variegated phenotypes produced offspring identical to their parent following selfing. In contrast, variants of nonpattern cultivars, when selfed, yielded offspring identical to the original cultivar, identical to the variant, or novel phenotypes. When variants were returned to culture, those derived from cultivars with PAV were more stable than those derived from nonpattern cultivars. In Coleus, micropropagation may induce epigenetic and/or heritable changes in leaf variegation. Cultivars with NAV are less stable than cultivars with PAV. Chemical names used; N-(phenylmethyl)-lH-purine-6-amine [benzyladenine (BA)].