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  • Author or Editor: Harrison Hughes x
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`Crimson Sweet' watermelon was transformed with a copper inducible ipt gene. Clonally propagated transformed and non-transformed plants were sprayed with three different concentrations (0, 50, 100 mm) of CuSO4 at the 2–3 leaf stage twice in a 24-hour period prior to their inoculation with fusarium wilt organisms. Plants were inoculated via root dip with two different isolates of Fusariumoxysporum sp. niveum Race 2. The pathogenic strains of Fusariumoxysporum sp. niveum Race 2, Fl 99-1, and Calg 15-19, were cultured on PDA solid medium and then transferred to a sterile flask filled with 50 mL of potato dextrose broth (PDB) liquid medium. These flasks were placed on a shaker at 100 rpm for 4–5 days before the inoculation date and the final concentration of 106 spores/mL was adjusted for inoculation. Roots of the experimental units were gently washed and were then infected by dipping them in to the beaker containing the isolates for 1 min. Inoculated plants were transferred to planting trays and maintained under growth chamber conditions. Plants then were watered as needed. Fusarium wilt symptoms initially appeared approximately 7–10 days after the infection. The Cu-ipt transformants exhibited a clear and significant resistance over non-transformed plants. The severity of disease development was relatively higher in the control Cu-ipt and non-transformed plants when compared to the plants treated with CuSO4. The control Cu-ipt plants were comparatively healthier than the control non-transformed plants. Infected plants were removed from soil 2 weeks after inoculation, washed and the stems were cut vertically for rating of browning of the vascular system.

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Grape cv. Valiant was micropropagated in an MS medium with and without 2% (W/V) of polyethylene glycol (PEG, MW 8000). Leaf anatomy of control (in vitro, no PEG), treated (in vitro, PEG), field grown and greenhouse grown plants were compared under light microscopy. Cell size, palisade layer formation, relative intercellular air space and apparent chloroplast number varied between the leaves of control and PEG treated (high osmoticum) plantlets. These leaf characteristics in the high osmoticum medium appeared more similar to the leaves of the greenhouse and field grown plants. Leaves from control plantlets contained cells of larger size, lacked normal palisade layer formation, greater intercellular pore spaces and fewer chloroplasts. Leaves of PEG treated plantlets had smaller cells, a more defined palisade layer, reduced intercellular pore spaces and greater number of chloroplasts. Leaves of greenhouse and field grown plants had small cells, a well-defined palisade layer, least intercellular pore space and greatest number of chloroplasts. These results demonstrate that a high osmoticum medium may be used to induce more normal leaf development.

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The merging of the Landscape Architecture Program (LA) with the Department of Horticulture had no effect on visibility of horticulture at Colorado State University and in the state. It did enhance the stature of the merged department as it became second only to the Department of Animal Sciences in terms of undergraduate majors and graduates in the College of Agricultural Sciences. The merger had only a limited impact on the budget. The LA is accredited. Accreditation standards aided the LA in justification of a new position. Since the merger, the Landscape Design and Contracting Program has become accredited through the Associated Landscape Contractors of America (Reston, Va.). Horticulture, which has no accrediting agency, is at a disadvantage in competing for open positions.

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Native turfgrasses have received greater attention in recent years because of their usefulness in growing in areas where many other grasses cannot. Saltgrass (Distichlis spicata) has good salt tolerance, but the natural germination rate for the seed is low. This is most likely due to the thickness of the seed coat inhibiting normal imbibition of water. Previous research in our laboratory has demonstrated increased germination with hand-scarification. The purpose of this research was to compare germination rates of machine-scarified, hand-scarified, and nonscarified seed. Scarifying the seeds by hand results in greater uniformity, but the operation is tedious and time-consuming. Machine scarification is quick, but the seeds have reduced uniformity. Two seed lots, one designated “Modoc” and one designated “Granite,” were compared in laboratory and field germination tests. Preliminary observations have shown that “Granite” seed had somewhat higher viability and vigor than the “Modoc” seed. Significantly greater germination occurred with scarification when seeds were germinated at 14 h of light at 30 °C and 10 h of darkness at 20 °C in the laboratory. Although scarification treatments were similar with the “Granite” seeds, near 80% germination, there were significant differences between hand and machine scarification with the”Modoc” seeds; hand scarified seed had greater germination. The field germination experiment had similar results to the laboratory experiments with “Granite” seed. However, scarification did not aid germination of “Modoc” seed. This is thought to be due to low vigor and associated death of seedlings prior to emergence. Preliminary data confirm the low vigor of the “Modoc” seed as compared to “Granite” seed.

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Distichlis spicata var. stricta (Torrey) Beetle is a native grass that tolerates salt, high pH, and some heavy metals. It has been proposed for use in several challenging environments, including mine spoils and salt-impacted areas of golf courses. But, its widespread use has been hindered by several factors, one of which is poor seed set. Because chromosome numbers are variable and some genotypes are aneuploids, there was concern that pollen viability in some genotypes was low. Pollen from several genotypes failed to germinate in vitro on four artificial media prepared with various levels of osmoticum. However, hand pollination in vivo resulted in profuse pollen germination for all genotypes tested. Germination on pollinated stigmas was observed at intervals beginning 2 h after pollination with a fluorescence microscope using aniline blue and acridine orange stains and in bright field using toluidine-O stain. Very young stigmas seemed unreceptive and, while pollen would germinate, the pollen tubes would not grow down through the style. On receptive stigmas, many pollen tubes grew down toward the egg and some reached it within 24 h. There was no evidence of impaired fertility. Aniline blue was the best method for observing pollen tube growth through the style, although toluidine-O was adequate for observing germination on the stigmatic surface.

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Inland saltgrass, Distichlis spicata var. stricta (Torr.) Beetle, is a native western U.S. grass that has potential in turf situations. Elite clones with outstanding potential have been selected. Poor seed production appears to be the main limiting factor for its use as turf in saline conditions. In order to better understand seed set, 40 genotypes were examined for chromosome number and morphology. Chromosome numbers of root tip metaphase spreads varied with the most common being 2n = 38. However, chromosome numbers of 39, 40, 42, and 74 were also observed. Meiotic examination of anthers revealed 19 bivalents for those with 38 chromosomes while those with 42 had 20 bivalents with 2 unpaired chromosomes. The unpaired chromosomes lagged at anaphase. Crosses among genotypes of different chromosome number have resulted in good seed set. Harvested seed are germinable and plants from these crosses are being grown for further studies.

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In this study, 11 species, hybrids, and color variants were characterized using randomly amplified polymorphic DNA (RAPD) analysis. Total genomic DNA was extracted using a 2% CTAB extraction buffer using fresh or frozen leaf material. The DNA was amplified using standard RAPD-PCR protocols utilizing 10-mer primers. All primers utilized exhibited a high degree of polymorphism in their banding patterns among the species and hybrids studied. The primers used produced ≈40 reproducible bands. It was possible to identify and uniquely distinguish all species and hybrids investigated using these bands.

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Freezing is the major abiotic stress that limits geographical distribution of warm-season turfgrasses. Prior studies have indicated variation in freezing tolerance in saltgrass clones. Therefore, this 2-year study examined the freezing tolerance of 27 saltgrass clones as related to collection sites in three zones of cold hardiness. Furthermore, these clones were evaluated for time of leaf browning in the fall with the intent to determine if there was a correlation between this trait and freezing tolerance. Rhizomes were sampled during 2004 and 2005 midwinters from clones established in Fort Collins, Colo., and then subjected to a freezing test. Saltgrass freezing tolerance was highly influenced by the climatic zone of clone origin in both years of the experiment. Clones with greater freezing tolerance turned brown earlier in fall in both seasons. Ranking of zones for the average LT50 was: zone 4 (–17.2 °C) < zone 5 (–14.4 °C) < zone 6 (–11.1 °C) in 2004 and zone 4 (–18.3 °C) < zone 5 (–15.7 °C) < zone 6 (–13.1 °C) in 2005. Clones from northern areas tolerated lower freezing temperatures better overall. This confirmed that freezing tolerance is inherited. Large intraspecific variation in freezing tolerance may be effectively used in developing cold-hardy cultivars.

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Efforts are ongoing at Colorado State University to develop turf-type saltgrass cultivars. Prior freezing studies have indicated variation in freezing tolerance in saltgrass lines. Therefore, this study was made to examine relative freezing tolerance of 27 saltgrass clones as related to collection sites in three zones of cold hardiness. Furthermore, these lines were evaluated for fall color retention with the intent to determine if there is a correlation with fall color and freezing tolerance. Saltgrass rhizomes were sampled in mid-winter 2004 from lines established in Fort Collins, Colo., and then subjected to a laboratory-freezing test. Saltgrass freezing tolerance was highly influenced by climate zones of clones' origin (P < 0.01) and genotypes within zones (P < 0.01). There was a high negative correlation between color retention in the fall and freezing tolerance (P < 0.01). Average freezing tolerance of saltgrass clones within zones of origin significantly differed among zones. Ranking of zones for least square mean LT50 (OC) was: zone 4 (–17.2) < zone 5 (-14.4) < zone 6 (–11.1). LT50 values in zone 4 ranged from –17.8 (accession 72) to –17.0 (accession 87). Clones in zone 5 showed LT50 values from –17.8 (accession A29) to –11.9 (accession A137). Zone 6 clones had LT50 values that ranged from –9.5 (accession C92) to –12.6 (accession C12). Large intraspecific variation in freezing tolerance may be effectively used in new cold hardy cultivar development. Environmental adaptation inherited by origin of clone is useful in defining clones' adaptation range and may along with fall color retention serve as a selection criterion in saltgrass cold hardiness improvement.

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Limited numbers of broad-leaved evergreen species grow well in the cold, dry plains of Colorado. The roundleaf buffaloberry, Sheperdia rotundifolia Parry, is a broad-leaved evergreen species that's adaptable to xeriphytic conditions of the Western states. Since little propagation information is available for this species, we studied procedures for clonal propagation with emphasis on tissue culture procedures. In this study, we evaluated the use of liquid media overlays on rapid propagation and the influence of node position on growth. A comparison of media overlay, transfer to fresh media and a control of no transfer (remained in same media) showed limited differences among treatments. Comparison of terminal, middle and basal node sections showed considerable differences. Sections from the middle produced more branches than the terminal and basal sections, though the branches were shorter than the terminal sections.

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