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  • Author or Editor: K. E. Johnson x
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Trunk diameter, yield, root sprout production, and tree mortality of `Redglobe' peach were evaluated over a 14 year period on 5 rootstocks; `Lovell', `Halford', `Nemaguard', `Bailey', and `Siberian C'. Trunk diameter in year 14 was not different for trees on `Lovell' and `Halford', with diameters on 23.7 and 23.5 cm respectively, as compared to 93 and 45 kg on `Halford'. These were not significantly different from each other. Both `Lovell' and `Halford' produced 1.8 root sprouts per tree or less both years. Trunk diameter on `Nemaguard', `Bailey', and `Siberian C' was different from `Lovell' and `Halford'. Yields on `Nemaguard', `Bailey', and `Siberian C' were 92, 88, and 41 kg respectively, in year 12, with trees on `Siberian C' being different from the other 4 rootstocks. Yields in year 14 were 60 kg on `Nemaguard', 50 kg on `Bailey', and 28 kg on `Siberian C'. Root sprout averages per tree on `Nemaguard' were 1.6 and 6.7 in years 8 and 14 while `Bailey' averaged 1.1 and 7.7. Root sprouts on `Siberian C' were low in year 8, but increased in year 14 to 15.1 per tree. Tree mortality on `Siberian C' was 44% by year 14.

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Controlled crosses of a Vermillion red flesh color cultivar with 4 normal red flesh color cultivars were made. F1, F2, and backcross generations were grown in the field and the fruits evaluated for flesh color. All fruits of the F1 generation were Vermillion. The F2 generation segregated to a 9:7 ratio of vermillion to normal in all crosses. The probabilities of fit ranged from 0.10 to 0.95. This ratio is indicative of two dominant genes with complementary effects or double recessive epistasis, Backcrosses to the dominant parent produced almost all vermillion flesh fruit. Backcrosses to the recessive parents did not fit any documented ratios. Further analysis of the BC generations seems to suggest that flesh color is controlled by two dominant genes.

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Controlled crosses of a Vermillion red flesh color cultivar with 4 normal red flesh color cultivars were made. F1, F2, and backcross generations were grown in the field and the fruits evaluated for flesh color. All fruits of the F1 generation were Vermillion. The F2 generation segregated to a 9:7 ratio of vermillion to normal in all crosses. The probabilities of fit ranged from 0.10 to 0.95. This ratio is indicative of two dominant genes with complementary effects or double recessive epistasis, Backcrosses to the dominant parent produced almost all vermillion flesh fruit. Backcrosses to the recessive parents did not fit any documented ratios. Further analysis of the BC generations seems to suggest that flesh color is controlled by two dominant genes.

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Seed of 15 watermelon cultivars were evaluated for germinating ability at sub-optimum temperatures. Seeds of each cultivar were exposed to 12.8, 15.6, 18.3, 21.1, and 30.0°C for 8 days in a germinator in accordance to standard seed testing rules. Radical emergence was evaluated on day 5 and day 8. None of the cultivars germinated at 12.8C after 8 days exposure. At 15.6°C, 'Red-N-Sweet' and `Blackstone' had germinations of 54 and 40 percent respectively on day 5, and both increased to over 80 percent on day 8. At 18.3°C `Red-N-Sweet' and `Blackstone' exhibited at least 90 percent germination after 5 days while the other 14 cultivars ranged from 2.5 to 86 percent. At 21.1°C all cultivars except `Black Diamond' and `Allsweet' had germinations of 80 percent or higher on day 5. Germination increased to 90 percent or above by day 8 except for `Black Diamond' at 83 percent. There were no significant differences among cultivars at the 30°C optimum germinating temperature with cultivars having 89.5 percent or higher germination.

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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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Abstract

Seedlings of ‘Topa Topa’ avocado (Persea americana Mill.) were grown in steamed loamy sand soil with no fertilizer, complete fertilizer (N, P, K, S, Ca, Mg, Cu, Zn, Mn, Fe, Mo, B), −P, −Zn, −P and −Zn, and −Zn+10 × P(640 ppm P). Seedlings were inoculated separately with one of 2 isolates of Glomus fasciculatus (Thaxter) Gerd. & Trappe (GF) or were inoculated with a water filtrate of the mycorrhizal inoculum plus autoclaved mycorrhizal inoculum. Growth of mycorrhizal seedlings was 49-254% larger than nonmycorrhizal avocados except at the −Zn+10×P regime where mycorrhizal and nonmycorrhizal avocados were of similar size. Both mycorrhizal isolates increased absorption of N, P, and Cu at all fertilizer treatments and absorption of Zn was increased with all fertilizer treatments by one mycorrhizal isolate. Fertilization with P did not alter P concentrations in leaves of nonmycorrhizal plants but increased P concentrations in leaves of mycorrhizal seedlings. Fertilization with 10×P increased P concentrations in both mycorrhizal and nonmycorrhizal seedlings. One GF isolate appeared to be superior to the other based on mineral nutrition of the host avocados. Differences between the isolates apparently were related to their rate of growth or ability to infect. Poor growth of avocado seedlings in steamed or fumigated soil can be related to poor mineral nutrition due to the destruction of mycorrhizal fungi.

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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

An inexpensive chamber for controlled freezing of large container-grown plants up to 2 m in height was constructed using liquid nitrogen as a refrigerant. A microcomputer-based system was developed to control the cooling sequence and to collect data on tissue temperature, air temperature, and exotherms. Versatile software was written that allowed the programmed rate of temperature drop to be based on either tissue temperature or air temperature.

Open Access

We investigated if salt tolerance can be inferred from observable cues based on a woody species’ native habitat and leaf traits. Such inferences could improve species selection for urban landscapes constrained by soils irrigated with reclaimed water. We studied the C3 tree species Acer grandidentatum Nutt. (canyon maple; xeric-non-saline habitat) that was hypothesized to have some degree of salt tolerance based on its semiarid but non-saline native habitat. We compared it with A. macrophyllum Pursh. (bigleaf maple) from mesic/riparian-non-saline habitats with much larger leaves and Eucalyptus camaldulensis Dehnh. (eucalyptus/red gum) from mesic-saline habitats with schlerophyllous evergreen leaves. Five levels of increasing salt concentrations (non-saline control to 12 dS·m−1) were applied over 5 weeks to container-grown seedling trees in two separate studies, one in summer and the other in fall. We monitored leaf damage, gas exchange, and hydric behavior as measures of tree performance for 3 weeks after target salinity levels were reached. Eucalyptus was the most salt-tolerant among the species. At all elevated salinity levels, eucalyptus excluded salt from its root zone, unlike either maple species. Eucalyptus maintained intact, undamaged leaves with no effect on photosynthesis but with minor reductions in stomatal conductance (g S). Conversely, bigleaf maple suffered increasing leaf damage, nearly defoliated at the highest levels, with decreasing gas exchange as salt concentration increased. Canyon maple leaves were not damaged and gas exchange was minimally affected at 3 dS·m−1 but showed increasing damage at higher salt concentration. Salt-tolerant eucalyptus and riparian bigleaf maple framed canyon maple’s moderate salt tolerance up to 3 dS·m−1 that appears related to seasonal soil drying in its semiarid native habitat. These results highlight the potential to infer a degree of salt tolerance from either native habitat or known drought tolerance in selecting plant species for urban landscapes limited by soil salinity or brackish irrigation water. Observable cues such as xeri-morphic leaf traits may also provide visual evidence of salt tolerance.

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Hand thinning is a necessary and costly management practice in peach (Prunus persica) production. Stone fruit producers are finding it increasingly difficult to find a workforce to manually thin fruit crops, and the cost of farm labor is increasing. A new “hybrid” string thinner prototype designed to adjust crop load in vase or angled tree canopies was evaluated in processing and fresh fruit plantings in varying production systems in four U.S. growing regions in 2009. Data were uniformly collected across regions to determine blossom removal rate, fruit set, labor required for follow-up green fruit hand thinning, fruit size distribution at harvest, yield, and economic impact. String thinner trials with the variable tree forms demonstrated reduced labor costs compared with hand-thinned controls and increased crop value due to a larger distribution of fruit in marketable and higher market value sizes. Blossom removal ranged from 17% to 56%, hand thinning requirement was reduced by 19% to 100%, and fruit yield and size distribution improved in at least one string-thinning treatment per experiment. Net economic impact at optimum tractor and spindle speeds was $462 to $1490 and $264 to $934 per acre for processing and fresh market peaches, respectively. Case study interviews of growers who thinned a total of 154 acres indicated that commercial adoption of string-thinning technology would likely have positive impacts on the work place environment.

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