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Matthew Arrington and Lisa Wasko DeVetter

. Consequently, reduced honey bee foraging during key pollination periods may negatively impact fruit set and other yield components in blueberry cultivated in western Washington and elsewhere in the PNW. In addition to the reduced foraging activity during

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Amy F. Iezzoni and Colleen A. Mulinix

Abbreviations: PC, principal component. We acknowledge the Michigan Agricultural Experiment Station for their support of this research. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations

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Derek W. Barchenger, Robert A. Clark III, Paul A. Gniffke, Dolores R. Ledesma, Shih-wen Lin, Peter Hanson and Sanjeet Kumar

is high and stable yield and yield components. Breeders must examine whether a given cultivar is better adapted to a specific type of environment, and whether its performance is stable relative to that of other cultivars. Predictable performance over

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Kent E. Cushman, Thomas E. Horgan, David H. Nagel and Patrick D. Gerard

Pumpkins (Cucurbita pepo, C. moshata) were grown in northern Mississippi during 2000 and 2001 for the purpose of more narrowly defining plant population recommendations for commercial production in the humid southeastern United States. Four plant populations were examined for `Aspen': 908, 1361, 2045, and 3068 plants/acre (2244, 3363, 5053, and 7581 plants/ha, respectively) and for `Howden Biggie': 605, 908, 1361, and 2045 plants/acre (1495, 2244, 3363, 5053 plants/ha, respectively). Plant populations were adjusted by varying in-row spacing while holding between-row spacing constant at 8 ft (2.4 m). Plant population significantly affected yield of `Aspen' and `Howden Biggie'. Linear and quadratic terms were significant for `Aspen', with maximum yield (ton/acre and fruit/acre) for the quadratic relationship occurring at about 2045 plants/acre. In contrast, yield of `Howden Biggie' decreased significantly (ton/acre) and nonsignificantly (fruit/acre) in a linear relationship as plant population increased from 605 to 2045 plants/acre. Plant population significantly affected fruit weight and size. As plant population increased, weight and size decreased slightly but significantly in a linear relationship for `Aspen' (lb/fruit and inch3/fruit) and `Howden Biggie' (lb/fruit). The quadratic relationship for `Howden Biggie' (inch3/fruit) was significant and the minimum value occurred at about 1361 plants/acre. Plant population significantly affected pumpkin yield components associated with plant productivity. As plant population increased, number and weight of fruit per plant decreased sharply in a quadratic relationship for `Aspen' (lb/ plant and fruit/plant) and `Howden Biggie' (lb/plant). The linear relationship for `Howden Biggie' (fruit/ plant) also decreased significantly. At the highest plant populations for `Howden Biggie', 40% of the plants did not produce marketable pumpkins. In conclusion, recommendations of optimum plant populations for a semi-vining cultivar such as `Aspen' should be centered on about 2045 plants/acre. Published recommendations from Kentucky appear sound, advocating plant populations within the range of 1360 to 2720 plants/acre (3361 to 6721 plants/ha). For a vining cultivar such as `Howden Biggie', recommendations can be as low as 605 plants/acre. Published recommendations from Kentucky and Georgia, along with those published in the Vegetable Crop Guidelines for the Southeastern U.S., advocate plant populations for vining cultivars of approximately 725 to 1465 plants/acre (1790–3620 plants/ha). Our results with `Howden Biggie', a cultivar that produces larger pumpkins than most other vining cultivars grown for the wholesale market, indicate that producers of vining cultivars should use plant populations from the lowest values of these recommendations or use even lower values. Our results also indicate that growers can control size and weight of pumpkins by varying plant population, with increasing populations resulting in a slight decrease of size and weight.

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D.S. NeSmith

Watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] cultivars StarBrite and Crimson Sweet were grown during 1991 and 1992 in rows 1.5 m apart at plant spacings of 0.9, 1.5, or 2.2 m. Total fruit yield, marketable fruit yield, fruit-weight distribution, and estimated gross returns were determined for each spacing treatment. Total and marketable fruit yields were greater overall for `StarBrite' than for `Crimson Sweet'. Except for 1991 `Crimson Sweet' yields, marketable fruit yields per unit land area increased 29% to 34% as plant spacing decreased from 2.2 to 0.9 m. The yield component contributing the most to increased yields with high-density plantings was increased fruit count per unit land area. Average fruit weight responded only slightly to decreased plant spacing. Fruit-weight distribution on a relative frequency scale was stable regardless of plant spacing or production year. The potential for increasing gross returns per unit land area exists by increasing watermelon plant populations beyond the current Georgia recommendation of 2500 to 3000 plants/ha.

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Geoffrey M. May and Marvin P. Pritts

The main effects and interactions of soil-applied P, B, and Zn on yield and its components were examined in the field at two pH levels with `Earliglow' strawberries (Fragaria × ananassa Duch.). Applied nutrients had significant effects on several yield components, but responses depended on the levels of other nutrients or the soil pH At a soil pH of 5.5, yield responded linearly to B and quadratically to P. At pH 6.5, P interacted with B and Zn. Fruit count per inflorescence was the yield component most strongly associated with yield followed by individual fruit weight. However, these two yield components responded differently to soil-applied nutrients. Foliar nutrient levels generally did not increase with the amount of applied nutrient, but often an applied nutrient had a strong effect on the level of another nutrient. Leaf nutrient levels were often correlated with fruit levels, but foliar and fruit levels at harvest were not related to reproductive performance. Our study identifies some of the problems inherent in using foliar nutrient levels to predict a yield response and demonstrates how plant responses to single nutrients depend on soil chemistry and the presence of other nutrients.

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Ana I. López-Sesé and Jack Staub

Three U.S.-adapted Cucumis sativus var. sativus L. lines and one C. sativus var. hardwickii (R.) Alef.-derived line were crossed in a half-diallel design to determine their combining ability for several yield-related traits (yield components). Six F1 progenies were evaluated in a randomized complete block design with eight replications in 1999 and 2000 for fruit number and length/diameter ratio (L:D), lateral branch number, number of female flowering nodes, and days to anthesis. Combining ability was significantly influenced (p < 0.05) by year for most of the horticultural traits examined. General combining ability (GCA) was significant for all traits in each year. Specific combining ability (SCA) was significant in magnitude and direction for only fruit number and days to anthesis. Data indicate that the C. sativus var. hardwickii-derived inbred line WI 5551 possessed SCA for yield component traits, and thus maybe useful for improving fruit yield in commercial cucumber.

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Gopi Upreti and Harry C. Bittenbender

Thirteen coffee genotypes (Coffee arabica) were evaluated for yield stability in fourteen environments within Hawaii. The yield components (fruiting nodes, fruits/node, and fruit size) were also evaluated for stability in four environments. Genotype yield and component were regressed against environmental mean yield and yield component to determine the stability of yield and the components of yield.

Cultivars with means above the grand mean, regression coefficients ≤ 1, and the coefficients of linear determination ≥ 50% were considered to be superior and have phenotypic stability. Stable and superior genotypes are less sensitive to environmental changes and are more adapted to favorable and unfavorable conditions than unstable genotypes.

`Catuai' was stable for both yield and the components of yield (fruiting nodes, and fruits/node) which directly contribute to the yield. The genotype `SL 28' was unstable but highly responsive to favorable environments for yield as well as yield components. Selection for the stability of yield should be considered in coffee breeding programmes to develop genotypes adapted to diverse environmental conditions in Hawaii.

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Nicholi Vorsa, Richard Novy and Kim Patten

WA State bogs of the cultivar `McFarlin' exhibit highly variable productivity. Yield and various fruiting characteristics were sampled in 14 WA `McFarlin' bogs, representing two growing areas. Significant differences were found for yield, fruit number/area, percent fruit set, flowers/upright, fruit/upright, fruit weight and seed number/fruit. The variable, flowers/upright, accounted for 69% and 75% of the observed variation for yield and fruit number/area, respectively. A multivariate analysis model accounted for 93% of the variation for yield with 3 variables: flowers/upright (69%), fruit weight (20%), and seed number (4%). Principal component analysis identified three `groups' based on fruiting characteristics. DNA fingerprinting suggests, that variability in yield and fruiting characteristics, has a genetic component.

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J. M. Hart, Arthur Poole, Kris L. Wilder and B. C. Strik

Cranberries (Vaccinium macrocarpon Ait.) require low rates of N fertilizer compared to many horticultural and agronomic crops. Excess N promotes vegetative growth at the expense of yield. Growers desire information about N fertilization to achieve optimum yields without overgrowth, Little information has been published about N rate and timing influence on cranberries in south coastal Oregon. An N rate and timing field experiment with Crowley and Stevens cultivars was established to answer grower questions. N was applied at 0, 18, 36 and 54 kg/ha in various combinations at popcorn (white bud), hook, fruitset, early bud, and late bud. Yield, yield components, (fruit set, number of flowering and total uprights, berry size, flowers per upright and the proportion of uprights that flower), vegetative growth and anthocyanin content were measured. After 2 years of treatments, N rate or timing had little influence on yield or yield components in the previously heavily fertilized Crowley bed. In the previously lightly fertilized Stevens bed, N rate increased yield, vine growth, and the number of flowering uprights, N timing also influenced the number of flowering uprights. The total number of uprights was influenced by the interaction of N rate and timing.