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  • Author or Editor: L.L. Davis x
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Significant research has been conducted on wildflower sod, but the reasoning behind the production system methods is not clear. The purpose of this research was to determine the influence of mowing height on the subsequent leaf growth and root biomass distribution in a wildflower sod production system. Rudbeckia hirta was grown in sand in polyvinyl chloride (PVC) tubes in simulating field conditions. Plants were either not mowed (control) or hand-clipped to 5.1, 7.6, or 10.2 cm to simulate mowing. After the initial mowing, plants were mowed at ≈7-day intervals. Total root depth, number of root axes in the top 2.5 cm, root: shoot ratio, total root dry weight, and root dry weight at depths of 0.0-2.5, 2.5-21.7, 21.7-40.8, and 40.8-60.0 cm were measured at the end of the study. Comparing the total root dry weight of all segments indicates that mowing significantly reduces root biomass. As mowing height increased, the depth of longest root increased linearly. Plants not mowed or plants mowed to 10.2 cm produced significantly more root axes in the top 2.5 cm of sand than did mowing heights of 5.1 or 7.6 cm. Root dry weight in the top 2.5 cm was considerably greater in nonmowed plants. Increased root axes in sod with higher mowing heights indicated a greater root density, which may also increase wildflower sod stability.

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Field-grown wildflower sod has been in production for several years, but as with any crop management system, the reasoning behind the methods is not always known. One characteristic of wildflower sod production that has been debated is the height at which the plant is maintained. The above-ground shoot growth is managed to reduce the damage to plants when undercut and to allow for ease of shipping. Growers typically use a height of 7.6 cm because this is the highest height allowed by many mowers. Also, root production is the key to forming a sod that will hold together well and withstand the rigors of undercutting, lifting, storage, and transplanting. The purpose of this study was to determine the influence of cutting height on the plant's ability to produce a sod. Rudbeckia hirta L. was used as a model wildflower species and was seeded into polyvinyl chloride (PVC) tubes 10.2 cm in diameter with a depth of 60 cm to simulate a field situation. To characterize shoot and root growth, during a period of 12 weeks plants either received no clipping or continuous clipping at heights of 5.1, 7.6, and 10.2 cm. Root dry weights were measured at depths of 0-2.54, 2.54-21.7, 21.7-40.8, and 40.8--60.0 cm. Leaf area measurements of the clippings were recorded to determine productivity. Results indicated that clipping the shoots of Rudbeckia hirta caused a decrease in root biomass.

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Water conservation in a landscape is an important issue because periodic water shortages are common in many regions of the world. This increases the importance of specifying landscape plants that require less water and matching the plant to site microclimates. Our objectives were to establish water-use rates for three herbaceous landscape plants and to determine the level of water reduction these plants can tolerate while maintaining both visual and landscape quality. Water use rates were determined for Schizachyrium scoparium (Little bluestem), Hosta spp. (Hosta) and Festuca cinerea `Dwarf' (Dwarf blue fescue) in studies using pot lysimeters at the Univ. of Nebraska Horticulture Research Greenhouse facility. Each lysimeter was watered to saturation, allowed to drain to field capacity, and weighed. The lysimeters were weighed again 24 h later, and the process was repeated to determine daily evapotranspiration. Results indicated that hosta used less water than dwarf blue fescue and little bluestem. In a subsequent study to compare the relative effects of withholding irrigation among these species, seven groups of five replicates of each species were grown in 1 peat: 0.33 vermiculite: 0.66 soil: 1 sand (by volume) in 7.6-L containers. Each container was watered to saturation, allowed to drain for 24 h to reach field capacity, and allowed to dry down in 10-day increments. Results of the dry-down study indicated that little bluestem maintained the best visual quality for the longest duration of drought, followed by dwarf blue fescue and hosta in decreasing order of visual quality.

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The rare plant, Fragaria multicipita Fern., was characterized by an unusual vegetative morphology that was long presumed to be suggestive of an ice front relict. While an additional species of Fragaria would be a potential source of genetic diversity for enhancing cultivated strawberry germplasm, evidence now indicates that such potential is not present in F. multicipita. Grafting of F. multicipita to F. chiloensis Duchesne resulted in transmission of a subgroup 16SrVI-B phytoplasma to, and the development of multicipital growth in, F. chiloensis. The results indicated that F. multicipita is a phytoplasma-diseased aberrant growth form of F. virginiana Duchesne and is an unfounded taxon. It is apparent that this plant population offers no unique potential for increasing genetic diversity in cultivated strawberry germplasm, but the phytoplasma may be capable of infecting commercial strawberry.

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Strawberry fruit phyllody, production of leaves and other vegetative organs from fruit tissue around achenes, has been ascribed to physiological causes due to temperature conditions during transplant cold storage, plant response to changing seasonal conditions at flower initiation time, and to phytoplasma infection. In examination of phylloid fruits from different strawberry clones and from different locations and sources, we found four distinct phytoplasmas associated with phyllody of strawberry fruit: strawberry multicipita (SM) phytoplasma (16S rRNA group VI, subgroup B), STRAWB2 phytoplasma (16S rRNA group I, subgroup K), clover yellow edge phytoplasma (16S rRNA group III, subgroup A), and a new group III phytoplasma. The SM and STRAWB2 phytoplasmas were detected in plants with phylloid fruit that also exhibited stunting and crown proliferation (SM phytoplasma) or stunting and leaf chlorosis (STRAWB2 phytoplasma). In no instances did we fail to detect phytoplasmas in phylloid fruit. To our knowledge, this is the first report to associate strawberry fruit phyllody with the presence of these phytoplasmas and to report that phytoplasmas other than those belonging to 16S rRNA group I (aster yellows group) can also be associated with strawberry fruit phyllody.

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Abstract

Minnesota 108 is a breeding line of pea (Pisum sativum L.) developed by cooperative effort of the Departments of Horticultural Science and Landscape Architecture and Plant Pathology. This germplasm combines near-commercial type and resistance to common root rot caused by Aphanomyces euteiches (Drechs.), and to fusarium wilt caused by Fusarium oxysporum f sp. pisi (Linford) race 1 Snyder & Hansen. It should be useful as a germplasm source for the transfer of root rot resistance to commercial cultivars by means of an improved testing technique (2).

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Abstract

‘Andover’ parsnip (Pastinaca sativa L.) is being released for commercial fresh-market and home garden production as a cultivar with desirable root type and resistance to field and storage attack by Itersonilia perplexans Derx. (1-4), which causes a foliar leaf spot, and, in storage, a root canker followed by root deterioration. The disease is commonly known as parsnip canker. A need for resistance to deterioration in storage gave rise to the breeding program. It was found that canker was a major reason for this deterioration, although other organisms are known to be involved.

Open Access

The susceptibility of 46 carrot cultivars to infection by Alternaria radicina Meier, Drechsler, and Eddy, causal agent of black rot disease, was evaluated in field trials with a toothpick inoculation method. Toothpicks infested with A. radicina were inserted into the shoulders of 10- to 12-week-old carrots (Daucus carota L.) and lesion areas were measured 9 to 10 weeks later. There were significant differences in lesion size among cultivars. Relatively resistant cultivars included `Panther' and `Caro-pak', and susceptible cultivars included `Royal Chantenay' and `Nogales'. Nine of the cultivars were inoculated with A. radicina-infested toothpicks and maintained in cold-storage for 10 weeks. Lesion development was greater in cold-storage than in the field, but the relative ranking of cultivars in terms of resistance to A. radicina was similar.

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This study was conducted to determine whether the type of pot used for the evaluation affected the resistance response of the sweetpotato plants, and to assess the resistance response to different root-knot nematode species. Five sweetpotato [Ipomoea batatas (L.) Lam] cultivars, `Beauregard', `Exce'l, `Jewel', `Hernandez', and `Porto Rico', were screened for M. incognita (race 3), Meloidogyne arenaria (race 2), and M. javanica, in both 10-cm-side, square pots and 4-cm-diameter, cone pots. Gall index, necrosis index, and number of nematode eggs per gram of root were used to estimate nematode-resistance reaction. Mean of all indices between the 2 pot types were not significantly different (α = 0.05). Gall and necrosis indices were not correlated in any of the cultivars. Resistance response depended on cultivars and nematode species for all variables analyzed. `Beauregard' was the most susceptible to Meloidogyne. `Hernandez' and `Excel' were found to be the most resistant cultivars to the Meloidogyne species.

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The toxic bait, Adios, was tested with the use of a trap crop in a field experiment at the Univ. of Nebraska during Summer 1998. The insecticide contains the secondary plant metabolites known as cucurbitacins that are highly attractive to the striped and spotted cucumber beetles, Acalymma vittatum and Diabrotica undecimuncata howardi, respectively. These beetles serve as the vector of the bacterial pathogen, Erwinia tracheiphila, which causes severe wilting and eventual death of susceptible cucurbits. The objective of the study was to determine whether treatments of Adios, when applied to a flowering trap crop of resistant squash plants, would lure the cucumber beetles away from the susceptible cucumber plants and reduce bacterial wilt. The study compared the effectiveness of a sprayed trap crop, the direct application of Adios to the cucumber plants and no treatment in a randomized complete-block design. A greater number of beetles were attracted to the sprayed and untreated cucumbers compared to the cucumbers surrounded by the treated trap plants. However, significant numbers of dead beetles were found near the sprayed cucumber plants. Untreated plants showed more feeding damage, diminished fruit quality, and an earlier observation date of wilt symptoms as compared to the other treatments. The treated trap plants and the direct application of Adios were effective in delaying infection in cucumbers compared to the untreated plants in the experimental plots. This treatment may be useful to home gardeners.

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