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  • Author or Editor: Charles E. Johnson x
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The glucose-6-phosphate dehydrogenase (G-6-PDH) and glucose oxidase methods are commonly adapted for plant invertase assay. A disadvantage of the G-6-PDH assay is the relatively high cost of the coupling enzymes and cofactors. A disadvantage of the glucose oxidase method, which uses a glucose kit (Sigma, 510-A), is the presence of high activities of acid invertase and alkaline invertase in the PGO enzyme formula (peroxidase and glucose oxidase), which gives a falsely high invertase activity value. An alternative and inexpensive coupled assay was developed for enzymatic assay of plant invertases. In this assay, ADP produced from phosphorylation of glucose and fructose (hydrolysis products of invertases) is coupled to oxidation of NADH by the enzymes pyruvate kinase and lactate dehydrogenase in presence of phosphoenolpyruvate and NADH. This method was compared with the glucose-6-phosphate dehydrogenase method by using protein preparations derived from plant materials of three different species. Statistical analysis indicated that the alternative assay was similar in accuracy to the glucose-6-phosphate dehydrogenase method, with an advantage of reducing the cost from $0.85 to $0.35 per assay.

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The common fig is a popular backyard fruit tree and grown in small orchards throughout the coastal regions of the southeastern U.S. Two commonly grown cultivars in coastal areas have distinct fruiting patterns which would be of interest to processors and marketers of summertime fruit. A study was conducted over a 5-year period to determine the fruiting characteristics of `Celeste' and `LSU Purple' figs. The 9-year-old orchard used for the study is located in St. Gabriel, LA. Annual results over a 5-year period indicated a longer and more productive fruit-bearing season for `LSU Purple' than `Celeste'. The fruit-bearing cycle for `LSU Purple' is about 4 weeks longer than is for `Celeste'. `Celeste' and `LSU Purple' exhibited different fruiting patterns over a 5-year period. `Celeste' consistently produced ripe fruit about one week before `LSU Purple' over the 5-year period. `Celeste' produced 85% of its total yield in a 2-week period with one main crop per year. However, `LSU Purple' produced two and sometimes three distinct crops each year. `LSU Purple' produced a greater total yield compared to `Celeste' with 6.45 kg/tree compared to 4.57 kg for `Celeste' during the 5-year evaluation. Additionally, `LSU Purple' retained foliage longer each year than `Celeste'; a characteristic perhaps due to a higher level of resistance to fig leaf rust. In areas where `LSU Purple' is adapted, this selection of fig may offer a more productive alternative to traditional cultivars planted.

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National demand for authentic Southern cuisine has contributed to the increased utilization of mayhaw fruit. Certain fruit characteristics are essential for the processing of mayhaw. Most of the mayhaw fruit used in processing comes from wild populations. Efforts are being made to identify superior clones from native populations. This study was undertaken to determine the chances of finding a superior clone with desirable processing attributes in a completely random population of mayhaw seedlings. Trees were removed from a 36 year-old mayhaw seedling orchard and relocated to a new orchard. The original orchard contained over 1500 trees. Five years after establishment in the new orchard, fruit were harvested from 75 of the trees and evaluated for fruit weight, percent malic acid, percent soluble solids, and color. Of the 75 trees, 48 were within one standard deviation of the mean trunk diameter. Seven trees fell below 12.1 cm and only 4 trees were larger than 19 cm. The mean fruit weight was 2.1 g with a range from 1.77-2.4 g. Sixty-seven percent of the trees produced fruit having weights within one standard deviation of the mean. Percent malic acid of mayhaw juice averaged 1.35% among the 75 trees. Seventy-two percent of the trees produced fruit with percent malic acid within one standard deviation of the mean. Mean percent soluble solids of mayhaw juice were 6.1 with a range of 5.36% to 7.01%. Seventy-three percent of the trees produced fruit with soluble solids percentages within one standard deviation of the mean. The probability of finding individuals in this population that exceeded the mean of these parameters (percent malic acid,%SS, and fruit weight) is less than 10%.

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Educational and research opportunities utilizing native plant species are being developed by the LSU Agricultural Center through the recent establishment of a native plant arboretum at the Calhoun Research Station. Plants indigenous to Louisiana and surrounding states are being collected and planted in the arboretum for evaluation of potential values for landscaping, in food industries, and/or wildlife management. Native trees being studied include species of oak (Quercus), maple (Acer), hickory (Carya), and dogwood (Cornus). Lesser known species of holly (Ilex) and hawthorn (Crataegus), are being evaluated for commercial production and landscape potential. Fruit being collected for field orchard studies include mayhaw (Crataegus opaca), pawpaw (Asimina triloba), and several native plums (Prunus spp.).

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Fruits from five mayhaw selections were harvested and frozen at –2 °C. Juice was extracted with a steamer and kept in storage at 5 °C until processing. Percent soluble solids, percent malic acid, initial pH, and color were then determined for postharvest characteristics. 550 mL juice was placed in a 2000-mL beaker and heated until boiling. Dry pectin mixed with a portion of the total sugar equivalent to 5–10 times the weight of the pectin was sprinkled into the boiling juice. Once pectin was in solution, the amount of sugar to obtain a ratio of ≈45 parts fruit: 55 parts sugar was added to the mixture. The mixture was cooked until the soluble solid reading reached 65% and then poured into jars to cool to room temperature. The five mayhaw jellies alone with one commercial apple and one commercial mayhaw were evaluated using a panel preference test. Evaluation was based on a scale from dislike extremely to like extremely. Preference scores indicated that mayhaw jellies were preferred to a commercially available apple jelly. There was a definite preference to deep red colored jellies. The specific varietal jellies were preferred to a commercially available mayhaw jelly.

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Field tests at two locations examined the influence of length and spacing of root propagules on blackberry plant establishment. Root propagules 10.2 cm long spaced 61 cm resulted in greater emergence, plant stand, and shoot growth than 5 cm and 2.5 cm root propagules. Differences in emergence and shoot growth between 10.2 cm progagules spaced 61 cm and 5 cm propagules spaced 61 cm were non-significant. Greenhouse tests compared four lengths of root propagules (15.2 cm, 10.2 cm, 5cm, 2.5 cm) for production of nursery plants. Percent emergence, time of emergence, and number of shoots per propagule produced from 2.5 cm propagules were comparable to results from 15.2 cm and 10.2 cm propagules.

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The peach breeding program in Louisiana was initiated in the late 1940's to develop adapted cultivars for Louisiana. The objectives of the program have been to develop large fruited disease resistant fresh market cultivars for all areas of Louisiana. The state is divided into three climatic zones in reference to the breeding program (north, south, and coastal). Cultivars have been developed that are adapted specifically for each zone. A few cultivars produce marketable fruit in all three zones. The annual chill units vary from 350 to 1000+ over the three zones. Seventeen cultivars have been released since 1969 and these are used throughout the southeast U.S. in production areas. A primary breeding objective is to develop a sequence of cultivars to service the market from late April through September. Also equally important is development of genetic disease resistance to bacterial spot, Xanthamonas campestris pv pruni.

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Home gardeners living in areas with alkaline water sources do not have easy or economically affordable means of acidifying irrigation water for vegetable production. One solution for achieving optimal vegetable yields using alkaline irrigation water is to grow the vegetables in a modified medium. To date, no medium on the retail market suits such growing needs. Therefore, medium recipes with varied levels (0, 4, or 8 lb/yard3) and sources of calcium [dolomitic lime, calcium sulfate (CaSO4)] and magnesium [dolomitic lime, magnesium sulfate (MgSO4)] were tested using an alkaline irrigation on ‘Oakleaf’ lettuce (Lactuca sativa), ‘Earliana’ and ‘Salad Delight’ cabbage (Brassica oleracea var. capitata), and ‘Snow Crown’ cauliflower (Brassica oleracea var. botrytis) crops. Additionally, crops were grown in two environments, under a high tunnel and on a nursery yard. High tunnel and nursery yard sites were used to test media performances in the presence of, and eliminating, rainwater to simulate container-grown vegetables growing in both a home garden situation and a commercial greenhouse production situation. The base mix of all media treatments in the study was 80 bark : 20 peat and fertilized with 12 lb/yard3 slow-release fertilizer at a rate of 1.8 lb/yard3 nitrogen (N), 0.5 lb/yard3 phosphorus (P), and 1 lb/yard3 potassium (K). This initial fertilizer application was incorporated to each medium before filling containers. Four treatments were tested against a commercially available medium, industry standard (IS) treatment (a commercially available bagged medium), and a control medium [treatment C (no supplemental calcium or magnesium fertilizer)] by supplementing the base mix with the following fertilizer levels: 4 lb/yard3 each of CaSO4 and MgSO4 (treatment 1); 4 lb/yard3 dolomitic lime (treatment 2); 4 lb/yard3 each of dolomitic lime, CaSO4, and MgSO4 (treatment 3); 8 lb/yard3 dolomitic lime (treatment 4). Media treatments 1 through 4 outperformed the IS and C media treatments in nearly all crops. All crops grown on the nursery yard, and cabbage grown under the high tunnel, had greater yields when grown in medium treatment 3, compared with the IS and C media treatments (P ≤ 0.05). All crops grown in medium treatment 2 on the nursery yard produced greater yields than the IS and C media treatments (P ≤ 0.05).

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Abstract

A production function was estimated for Ligustrum japonicum L. A medium comprised of 1 peatmoss: 2 sand: 2 pinebark with 10.8 g of fertilizer and 19.3 liters of water per container provides for the least cost production of a “salable” 70 g (dry weight) plant. The method is outlined for determining economic optimality for salable production.

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