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  • Author or Editor: Lynn E. Long x
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Cotyledon explants were harvested from immature walnut fruits during July and August 1991. Media consisted of either WPM with 0.1 μM 2,4-D, 5.0 μM TDZ and 1.0 g/liter casein hydrolysate or DKW with 4.4 μM BA, 0.05 μM IBA, 9.3 μM Kinetin and 250 mg/liter l-glutamine. Treatments were arranged factorially with 2 gelling agents, 7 g/liter Sigma agar or 2 g/liter Gelrite and were incubated in light or in darkness. After 4 weeks, all explants were placed on basal DKW with no growth regulators and were cultured in darkness. The best treatment tested was from seeds collected 14 weeks post-anthesis on WPM, agar, and incubation in light (22 embryos/explant, 78% embryogenesis). Use of DKW and gelrite in darkness resulted in 1 embryo/explant and 38% embryogenesis. Up to 90% shoot organogenesis also occurred on cotyledon explants from seeds collected 16 weeks post-anthesis and placed on WPM. Shoots elongated on stationary liquid DKW with 10 μM BA.

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Genetic transformation studies are aided by use of selection agents, such as antibiotics or herbicides. To determine the level of kanamycin to be used as a selection agent, cotyledonary stage somatic embryos from J. nigra lines J26 and J28, J. nigra × J. hindsii line S11, and J. regia line SU2 were placed on gelrite solidified WPM with 1 g/liter casein hydrolysate and 250 mg/liter cefotaxime and 3% (w/v) sucrose. Dosages for inhibiting secondary embryogenesis were 40 mg/liter kanamycin for J. nigra and J. nigra × J. hindsii and 100 mg/liter for J. regia. For the bialaphos experiments, somatic embryos of J. nigra lines J26 and J28 and J. nigra × J. hindsii line S11 were cultured on gelrite solidified LP medium with 0.5 g/liter casein hydrolysate and 3% (w/v) sucrose. Between 0.1 and 1.0 mg/liter bialaphos, inhibited secondary embryogenesis.

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A field trial was conducted on a Cherryhill silt loam soil at The Dalles, OR, from 2006 to 2008. The impacts of switching from the traditional micro sprinkler irrigation (MS) to double-lateral drip irrigation (DD) and from no groundcover with herbicide control of weeds (NC) to in-row wheat (Triticum aestivum) straw mulching (ST) were evaluated in a split-plot design with four replicates. Irrigation water use, mineral nutrition, and productivity of ‘Lapins’ sweet cherry (Prunus avium) on ‘Mazzard’ rootstock (P. avium) and soil quality were measured on a plot basis. DD reduced irrigation water consumption by 47.6% to 58.2% compared with MS. Straw mulch lowered irrigation water use by 9.7% relative to NC. Total fruit yield and fruit quality of firmness, size, and sugar at harvest were similar for the irrigation treatments. Straw mulch increased fruit size by 0.6 mm on average relative to NC, which could result in increased grower profitability. The DD system enhanced percentage of marketable fruit by 8.6% relative to MS. Leaf phosphorus (P), boron (B), zinc (Zn), and iron (Fe) concentrations were reduced with DD over MS; consequently, more P, B, Zn, and Fe fertilizers might be needed under DD. Straw mulch markedly decreased the populations of flagellates and amoebae but slightly increased the population of ciliates. Straw mulch resulted in a soil microbial community with remarkably less protozoa. Overall, DD is a viable alternate irrigation system for producing sweet cherry orchards with limited water resources for irrigation. Switching from NC to ST could lower irrigation water use, reduce herbicide runoff, and protect soil from erosion.

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