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Kristine M. Lang and Ajay Nair

between 2007 and 2012 (U.S. Department of Agriculture [USDA], National Agricultural Statistics Service, 2014 ). A high tunnel is a solar-heated, passively ventilated, plastic-covered structure that lengthens the growing season for high-value specialty

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C.O. Gwathmey and A. E. Hall

Removal of pods from legume crops may extend reproductive duration by delaying leaf senescence. In two years of field experiments, cowpea (Vigna unguiculata [L.] Walp. cv. CB5) pods were continuously harvested as they reached color–break or southernpea stage. The largely monocarpic reproductive pattern of non-picked CB5 was altered to a bimodal distribution by picking. During the first podding period, removal did not appreciably change reproductive duration nor the number of pods produced. It reduced dry weight in seed 22–34% and significantly delayed leaf senescence relative to the non–picked control. This increase in source:sink ratio was accompanied by increasing starch concentrations in stems and was followed by generation of a second set of pods which doubled the reproductive duration of picked plants. By contrast, starch reserves declined during the first podset in senescent control plants, which produced few pods thereafter. Picked plants produced 41–60% more pods/m2 over the entire season than non–picked CB5, but total dry weight in seed did not differ significantly since pod removal limited aced fill.

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Gouchen Yang and Paul E. Read

BA, IBA and GA3 were incorporated into softwood tissues to be cultured in vitro or rooted as cuttings by adding the plant growth regulators (PGR) at various concentrations to a forcing solution containing 200 mg/l 8-hydroxyquinoline citrate and 2% sucrose. BA and GA3 helped break bud dormancy in autumn-collected stems and increased percent bud-break. IBA inhibited bud break and shoot elongation. Rooting of forced softwood cuttings was enhanced by IBA in the forcing solution, while GA3 inhibited the rooting of plant species tested. When dormant stems were forced with periodic additions of BA (10 mg/l) in the forcing solution, in vitro shoot proliferation was enhanced. However, inclusion of GA3 in the forcing solution reduced shoot proliferation. A pre-forcing NaOCl soak and a pre-forcing treatment with wetting agents accelerated bud break, size and number of shoots available for both micro- and macro-propagation of the woody plant species tested. The forcing solution protocol described is an effective PGR delivery system and it can be used by the propagator to extend the season for obtaining softwood growth suitable for use as in vitro explants or softwood cuttings.

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Marvin D. Butler and Robert E. Rush

Early maturity is of major importance to table grape producers in Arizona and the California desert. However, table grapes in this region often experience a delayed and erratic budbreak thought to be due to a lack of chilling. The influence of three rates of hydrogen cyanamide on budbreak timing and uniformity was evaluated at a commercial vineyard near Dateland, Ariz., during the 1984-85 season. Treatments were made to three table grape cultivars over three application dates. Additional research to evaluate possible interaction between time of pruning and application of hydrogen cyanamide was conducted during 1985-86. Of the three application rates evaluated, the 5% solution provided optimal results, inducing a greater total number of buds to break for perlette and flame seedless cultivars than nontreated plots. Early application resulted in a significantly earlier but extended budbreak; later applications were more dramatic and uniform. Budbreak was accelerated by 1 to 2 weeks for perlette, and up to 2 to 3 weeks for flame seedless and Thompson seedless cultivars. Hydrogen cyanamide applications also had a positive influence on earliness of blossom and percent soluble solutes at harvest. Pruning up to 11 days before or 14 days after application of hydrogen cyanamide generally did not have a significant effect on budbreak or maturity at harvest.

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J. R. Heckman, D. J. Prostak, and W. T. Hlubik

The presidedress soil nitrate test (PSNT) is an in-season soil test that evaluates the N supplying capacity of soil before side dressing to adjust N application rates. Increasing acceptance of this soil test among field corn growers in New Jersey has shown it to be an effective practice. Nitrogen application rates were reduced by an average of 45 kg-1 ha without loss of crop yield. Field calibration research to extend use of the PSNT to sweet corn has the potential to improve N fertilizer recommendations for this crop. A critical concentration of 25 mg kg-1 NO3-N in the surface 30 cm of soil is generally considered adequate for field corn. Certain crop features of sweet corn (earlier harvest, smaller plant size and population) suggested that the critical NO2-N level might be lower than for field corn while market quality suggested that it might be a higher value. Results from 40 sweet corn field calibration sites in New Jersey indicate that the PSNT critical soil NO3-N concentration may be greater for sweet corn than field corn. A preliminary critical level of 30 mg kg-1 NO3-N in the surface 30 cm of soil is suggested for use of the PSNT on sweet corn. Further research is being conducted to improve sidedress N recommendations based on the PSNT.

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Michael A. Fidanza and Peter H. Dernoeden

Rhizoctonia blight (RB), incited by Rhizoctonia solani Kühn, is a common disease of cool-season turfgrasses. This 2-year field study was conducted to determine the influence of N source, N application timing, and fungicide treatment on RB severity in `Caravelle' perennial ryegrass (Lolium perenne L.). Ringer Lawn Restore (Ringer), a slow-release N source, was compared to water-soluble urea. Nitrogen was applied according to either a spring (March, May, June, and September) or fall (September, October, November, and May) schedule. Plots received either N only or N plus the fungicide iprodione (3.1 kg a.i./ha applied at 21-day intervals). RB was reduced with fall-applied Ringer compared to spring-applied urea in both years in fungicide-free plots. Nitrogen generally enhanced foliar mycelium growth and RB during the initial infection periods (i.e., late June to late July). By mid- to late August there were extremely high levels of blighting among all fungicide-free treatments. Nitrogen source and N application time had no effect on the level of blighting in iprodione-treated plots. During early disease outbreaks, iprodione did not always prevent foliar mycelium from appearing, but it did protect turf from severe RB. Iprodione reduced blighting, but the level of disease suppression and resulting turfgrass quality provided on the extended spray interval was not acceptable for high-quality golf course fairways. Chemical name used: 3-(3,5-dichlorophenyl)-N-(1-methylethyl)-2,4-dioxo-1-imidazolidine carboxamide (iprodione).

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G. Tehrani and W.D. Lane

Sweet cherry breeding started at Vineland and Summerland in 1915 and 1924 and has resulted in the naming and introduction of 11 and 18 cultivars, respectively. `Victor' and `Van' were the first cultivars named from Vineland and Summerland, respectively, in 1925 and 1944. `Van' has become a popular cultivar in North America and Europe. The main objective in these breeding programs has been to develop cultivars that produce large quantities of firm-fleshed, crack-free, flavorful, large, black cherries with a range of maturity dates to extend the season of harvest. In the 1960's, the development of self-fertile cultivars was added to the objective of the programs. Already several self-fertile cultivars and advanced breeding selections have been named and introduced from Canada. The programs have also contributed to the assignment of cultivars to different pollen-incompatibility groups and verification of pedigree of sweet cherry cultivars. The impact of these long-term breeding programs in Canada and abroad will be discussed in detail.

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William M. Randle and Rachel Snyder

Mild onion consumption is increasing in the U.S. The ability to produce mild onions depends on selecting proper cultivars and growing them in an appropriate environment. A major decision in producing onions with mild flavor is determining when to stop applying sulfate to the crop. While adequate sulfur is necessary for good early onion growth, high levels of sulfur increase bulb pungency. A study was conducted where sulfate was eliminated from the fertility program at biweekly intervals during onion growth and development. Mature bulbs were then analyzed for flavor precursors and their biosynthetic intermediates, and pungency. Pungency linearly increased from 3.7 to 5.1 μmols pyruvic acid from the earliest cut-off date to the latest cut-off date, respectively. While total milligrams of flavor precursors did not significantly change in response to sulfate elimination, the methyl cysteine sulfoxide: 1-propenyl cysteine sulfoxide ratio did. Methyl cysteine sulfoxide concentration decreased in a quadratic manner while 1-propenyl cysteine sulfoxide linearly increased as sulfate fertility was extended in the growing season. Changes in individual precursors will significantly affect flavor perception as well as flavor intensity.

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Farrell C. Wise, Laura L. Greenwood, and D. Bradley Rowe

Clonal propagation of recalcitrant conifers like loblolly pine depends on producing juvenile cuttings on hedges sheared several times annually. Although dormant cuttings root well, it will be economically important to also root softwood shoots produced between shearings. Several variables were therefore evaluated in a factorial experiment to enhance rooting and handling of summer cuttings. Rooting percentages were equivalent for 3 media after a 5-week hardening period (56% overall), but open flats of 1 perlite:1 vermiculite induced larger root systems at the end of rooting and hardening phases. Extending the rooting period from 10 to 14 weeks increased rooting from about 45% to 58% by the end of hardening. Primary root length per cutting increased 12-63% during hardening, depending on medium. After transplanting, overwintering survival was 98%. Foam rooting wedges produced smallest root systems, and resulting plants were consistently shortest through the following growing season. Weekly applications of soluble fertilizer during the last 6 weeks of rooting did not improve rooting or subsequent growth

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Loretta J. Mikitzel, Max E Patterson, and John K. Fellman

Walla Walla Sweet onions (Allium cepa L.) have a short storage and marketing season. Studies to determine viable shelf life and to extend post-harvest life with controlled atmosphere (CA) storage were conducted. Onions were exposed to various CA gas mixtures in combination with heat curing (35°C) and/or chlorine dioxide (ClO2) fumigation, to control disease. Preliminary results indicated Botrytis was the primary cause of post-harvest losses. A 1% O2, 5% CO2 atmosphere appeared to maintain onion quality better than other gas mixtures tested during 15 weeks of CA storage (0°C). Carbon dioxide series above 5% show promise in reducing the 35% storage loss that occurred with the 5% CO2 treatment. Curing for at least 72 hours followed by a 1-hour ClO2 fumigation resulted in the least bulb decay and after 15 weeks of storage (1% O2, 5% CO2), 75% of the bulbs were in marketable condition. Onions stored 15 weeks in air (0°C, 70% RH) were unmarketable. Shelf life of freshly harvested onions was 18 days, after which the onions rapidly decayed. After CA storage, shelf life was reduced to 10-14 days due to rapid sprouting. To enjoy a 30-day market window, disease control is necessary for freshly harvested onions and sprouting must be controlled in post-storage onions.