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Andrew G. Reynolds, Margaret Cliff, Douglas A. Wardle, and Marjorie King

Eighty-five cultivars, selections and clones of winegrapes (Vitis) from European breeding and selection programs were evaluated between 1993–95 in a randomized completeblock experiment. These included selections from Alzey, Freiburg, Geilweilerhof, Geisenheim, Weinsberg, and Würzburg (Germany); Hungary; and the former USSR. Vines were grown under an organic management regime that included sodium silicate sprays for powdery mildew (Uncinula necator) control and oil + detergent for insect control but with little to no nitrogen or other nutritional inputs. The Weinsberg cultivars Heroldrebe and Helfensteiner showed promise viticulturally and sensorially as alternatives to `Pinot noir'. Cultivars from Geisenheim (`Gm 7117-10' and `Gm 7117-26') and Würzburg (`Cantaro' and `Fontanara') appeared promising as `Riesling' alternatives; many displayed similar sensory characteristics to `Riesling', along with reasonable viticultural performance. Cultivars selected at Alzey (`Faberrebe'), Freiburg (`Nobling'), and Weinsberg (`Holder') displayed sensory characteristics superior to the standard cultivar Müller-Thurgau, with very intense muscat, pear, fig, and spicy aromas and flavors. Several muscat-flavored Hungarian white wine cultivars appeared to be superior viticulturally and sensorially to the standard `Csabagyongye'; these included `Kozma Palne Muscotaly', `Zefir', and `Zengo'. Miscellaneous red wine cultivars that showed promise included Geilweilerhof cultivar Regent, and Hungarian selections Kozma 55 and Kozma 525. Vine yields decreased substantially in the 3-year evaluation period, primarily due to lack of nitrogen. Many of these cultivars appeared to be highly adaptable to viticultural regions where cold winters and low heat units during fruit maturation presently restrict cultivar choices.

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Michael D. Richardson, John McCalla, Tina Buxton, and Filippo Lulli

Many early spring bulb species are naturally found in grassy areas such as meadows or lawns. However, few studies have been conducted to define this concept in maintained lawns, especially warm-season lawns such as zoysiagrass (Zoysia japonica) or bermudagrass (Cynodon dactylon). Four early spring bulb species, including two crocus species (Crocus tommasinianus ‘Ruby Giant’ and Crocus chrysanthus ‘Goldilocks’), reticulated iris (Iris reticulata ‘Cantab’), and snowdrop (Galanthus elwesii) were established in a zoysiagrass lawn site in Fall 2010. In Spring 2011 and 2012, five common preemergence herbicides used on lawns were applied across the plots to determine phytotoxicity. In addition, mowing treatments were started on plots at two timings (15 Mar. and 15 Apr.) to determine how mowing might affect survival and performance of the bulb species. Early performance was good for all bulb species and greater than 50% flower production was observed in the first spring (2011) after planting. However, in the subsequent 3 years (2012–14), the only species that persisted and continued to flower adequately each spring was ‘Ruby Giant’ crocus. Herbicides and mowing did not affect bulb survival or performance in the trial, suggesting that typical lawn management practices will not be deleterious to the bulbs. These results demonstrate that early spring bulbs may be incorporated into dormant, warm-season lawns, but species and cultivar selection will be crucial for long-term performance.

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U.K. Schuch, J.A. Bethke, and R.A. Redak

Water stress and N fertilization can have a profound effect on populations of phytophagous insects. While species and cultivar selection can identify plants that are resistant to common insect pests, cultural practices may further decrease the susceptibility to insect attacks. Six poinsettia and six chrysanthemum cultivars were grown under well-watered or water-deficient conditions, and three fertilizer regimes with low, medium, or high concentrations of N. Vegetative plant growth and longevity and fecundity of various insect pests on these plants were determined. Host plant suitability to insects was estimated by the quantity of foliar soluble protein. Low irrigation reduced leaf area and leaf and stem dry weights 36% to 41% in poinsettias and 26% to 28% in chrysanthemum. Leaf area and leaf dry weight increased linearly in response to increasing fertilizer concentrations in poinsettia and chrysanthemum. Cultivar-specific differences were found for all variables of vegetative growth in poinsettiasand chrysanthemum. Cultivar also strongly affected insect preference, development, and fecundity. Low irrigation significantly reduced insect survivorship of the silverleaf whitefly on poinsettias. On chrysanthemum, leafminers, thrips, and melon aphids were unaffected by irrigation or fertilizer treatments. Chrysanthemum cultivar choice strongly affected the number of insects or development time.

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U.K. Schuch, J.A. Bethke, and R.A. Redak

Water stress and N fertilization can have a profound effect on populations of phytophagous insects. While species and cultivar selection can identify plants that are resistant to common insect pests, cultural practices may further decrease the susceptibility to insect attacks. Six poinsettia and six chrysanthemum cultivars were grown under well-watered or water-deficient conditions, and three fertilizer regimes with low, medium, or high concentrations of N. Vegetative plant growth and longevity and fecundity of various insect pests on these plants were determined. Host plant suitability to insects was estimated by the quantity of foliar soluble protein. Low irrigation reduced leaf area and leaf and stem dry weights 36% to 41% in poinsettias and 26% to 28% in chrysanthemum. Leaf area and leaf dry weight increased linearly in response to increasing fertilizer concentrations in poinsettia and chrysanthemum. Cultivar-specific differences were found for all variables of vegetative growth in poinsettiasand chrysanthemum. Cultivar also strongly affected insect preference, development, and fecundity. Low irrigation significantly reduced insect survivorship of the silverleaf whitefly on poinsettias. On chrysanthemum, leafminers, thrips, and melon aphids were unaffected by irrigation or fertilizer treatments. Chrysanthemum cultivar choice strongly affected the number of insects or development time.

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Quirien. E.A. van Oirschot, Debbie Rees, and Julia Aked

Sweet potato is an important staple food crop in East Africa, but under local marketing conditions it has a shelf life of generally no longer than 2 weeks. As a result, the potential for marketing over longer distances is limited. The role of changes in sensory properties and weight loss as limiting factors for shelf-life were investigated. The important sensory attributes of five sweet potato cultivars were determined in discussion sessions with four taste panels and were: floury, sweet, chestnutty, grainy, smooth, soft, fibrous, discoloration, and moist. The sensory profiles of the five cultivars (KSP20, Kemb10, Yanshu 1, Pumpkin, and SPK004) differed significantly (P < 0.001). However, after 4 and 8 weeks under simulated tropical storage conditions (26 °C, 80% to 90% RH) no significant changes in the attributes were detected in most cases (P > 0.05). Changes in sensory properties were therefore not considered to limit shelf life. Shelf life experiments in Tanzania under simulated marketing conditions (26 + 5 °C, 50% to 60% RH) with 29 local cultivars revealed that roots with high rates of weight loss also rot rapidly. It was found that weight losses (primarily due to water loss) were high and varied significantly among cultivars (12% to 45% loss in 21 days). Further studies will investigate the structure and strength of the periderm as the main barrier to water loss to facilitate future cultivar selection.

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Michelle M. Wisdom, Michael D. Richardson, Douglas E. Karcher, Donald C. Steinkraus, and Garry V. McDonald

Early-spring flowering bulbs can increase biodiversity while adding color to lawns and other grassy areas. However, few studies have investigated whether bulbs can flower and persist in warm-season lawns or provide feeding habitat for pollinating insects. Thirty early-spring flowering bulbs, including species of Anemone, Chionodoxa, Crocus, Eranthis, Hyacinthus, Ipheion, Iris, Leucojum, Muscari, and Narcissus, were established in bermudagrass (Cynodon dactylon L. Pers) and buffalograss [Buchloe dactyloides (Nutt.) J.T. Columbus] lawns in late autumn 2015 in Fayetteville AR. Bulbs were assessed over three growing seasons for flowering characteristics, persistence, and their ability to attract pollinating insects. A growing degree day model was also developed to predict peak flowering times in our region. Numerous bulb entries produced abundant flowers in bermudagrass and buffalograss lawns in the first year after planting, but persistence and flower production were reduced in both the second and third years of the trial. Five bulbs persisted for multiple years in both turfgrass species and continued to produce flowers, including Crocus flavus Weston ‘Golden Yellow’ (crocus), Leucojum aestivum L. (spring snowflake), Narcissus (daffodil) ‘Baby Moon’, Narcissus ‘Rip Van Winkle’, and Narcissus ‘Tete-a-Tete’. Several bulbs, primarily crocuses and Muscari spp. (grape hyacinth), were also observed to attract pollinating insects, principally honey bees (Apis mellifera). These results demonstrate that some early-spring bulbs can persist in competitive warm-season turfgrasses, while providing pollinator forage, but species and cultivar selection is critical for long-term success.

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Danny L. Barney

During the 1800s and early 1900s, red and white currants (Ribes L. subgenus Ribes), black currants (Ribes subgenus Coreosma), and gooseberries (Ribes subgenus Grossularia) were grown commercially in the United States. Because Ribes serve as alternative hosts of white pine blister rust (Cronartium ribicola J. C. Fischer) (WPBR), which was introduced from Europe, the federal government and many states either banned or severely restricted currant and gooseberry production beginning about 1933. The development of WPBR resistant pines and black currants (the most susceptible cultivated Ribes) renewed interest in commercial Ribes production. Climatic and soil conditions in selected areas of the U.S. inland northwest and intermountain west (INIW) are favorable for commercial currant and gooseberry production. Challenges to the establishment of a Ribes industry are labor, marketing, diseases, and pests. Careful site and cultivar selection are critical for successful commercial production. This article describes Ribes opportunities and risks associated with currant and gooseberry production in the INIW. The region includes Idaho and surrounding areas in Montana, Nevada, Oregon, Utah, Washington, and Wyoming.

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Christopher B. Watkins

The tolerances of horticultural commodities to CO2 are outlined, as are also the associated biochemical and physiological aspects of differences in tolerance between and within commodity types. These tolerances are related to responses to the use of modified atmosphere packaging (MAP) during storage. Commodities vary widely in their responses to elevated CO2, and low tolerance to the gas limits its use to maintain quality in some cases. Standard recommendations are generally those established to extend the storage period of any given commodity as long as possible, and safe atmospheres may differ substantially for shorter term exposures used in MAP. Use of MAP for storage of minimally processed products represents an important example of this, as storage periods and quality attributes required for commercial marketing of cut products can be very different from those of the whole product. Factors such as cultivar and postharvest treatment before imposing high CO2 can influence responses of commodities to CO2, but are rarely considered in cultivar selection or in commercial application. A better understanding of the physiology and biochemistry of commodity responses to CO2 is required for increased use of MAP.

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Bobby D. McCaslin, Michael R. Hughes, and Arden A. Baltensperger

Abstract

A field experiment was conducted to determine if the turf quality of bermudagrass (Cynodon dactylon L. Pers.) was influenced by an interaction of genotype and nitrogen fertilization. The currently recommended level for maintenance of adequate quality in New Mexico bermudagrass turf is 48 kg N/ha per month during the growing season, the highest rate used in the study. The response of 10 bermudagrass genotypes, ‘Common’, ‘FB 49’, ‘FB 119’, ‘FB 133’, ‘N-7’, ‘NM-B1’, ‘Ormond’, ‘Santa Ana’, ‘Tifgreen’, and ‘Texturf 10’ were evaluated at N levels of 0, 16, 33 and 48 kg N/ha per month during the growing season. Color, density, and clipping yield responses of the genotypes differed for the four N fertility Ievels.‘Texturf 10’ had the highest overall ranking at 48 kg N/ha per month and ‘Ormond’ had the highest ranking at 32 and 16 kg N/ha per month. Thus, cultivar selection must be considered in arriving at precision N fertilization of bermudagrass turf.

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Catherine M. Grieve, Stacy A. Bonos, and James A. Poss

Six selections of Kentucky bluegrass (Poa pratensis L.) cultivars, selected based on their drought tolerance under field and growth chamber conditions in New Brunswick, N.J., were evaluated for salt tolerance based on yield and growth rates at eight soil water salinities [2 (control), 6, 8, 10, 12, 14, 18, and 22 dSm-1] from Apr. to Sept. 2005 in Riverside, Calif. Cultivars Baron and Brilliant were selected as drought sensitive and `Cabernet', `Eagleton', and `Midnight' were selected as drought tolerant. A Texas × Kentucky bluegrass (Poa arachnifera × Poa pratensis) hybrid selection (identified as A01-856) developed for improved drought and heat tolerance was also included. Vegetative clones were established in a randomized complete-block design with three replications, each containing 11 clones. Cumulative biomass and clone diameters were measured over time to evaluate relative yields and growth rates for the six cultivar selections. Based upon maximum absolute biomass production as a function of increasing EC, the order of production was `Baron' > `Brilliant' > `Eagleton' > `Cabernet' ≥ `Midnight' > A01-856. Yield relative to the non-saline control (2 dSm-1) for each cultivar was similar, except that the differences between cultivars were less pronounced, and `Baron' slightly outperformed `Brilliant'. Clone area expansion rates were analyzed with a phasic growth model and beta, the intrinsic growth rate of the exponential phase parameter, significantly varied with salinity. Ranking of cultivars, based on expansion rates, was similar to that based on cumulative biomass. Salinity tolerance in this experiment did not appear to be related to the observed ranking for drought tolerance.