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D. M. Glenn and W. V. Welker

The effect of ground covers on water uptake was studied using peach trees grown in a 4-part split root system. In 1992, one section of the root system was in bare soil and 3 sections were in combination with `K-31' tall fescue. In 1993, K-31 was eliminated in 2 additional sections, leaving 1 section in combination with `K-31'. When grass transpiration was suppressed by covering the K-31, tree water uptake/cm of root length was greater in the presence of grass compared to bare soil under well watered conditions. These data indicate that peach trees compensate for interspecific competition by increasing root hydraulic conductivity.

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John M. Rariden and Douglas V. Shaw

Runner plants from 16 strawberry (Fragaria ×ananassa Duch.) cultivars were grown using annual Mediterranean production systems to test for differences in productivity, performance traits, and vegetative growth attributes. Genotypes were included from germplasm adapted to four geographic regions: California and northwestern, northeastern, and mid-Atlantic or southeastern United States. The California genotypes were divided further into day-neutral and June-bearing categories. With these treatments, California cultivars had significantly larger plants and grew more rapidly during the fall and winter, had larger fruit, and produced at least twice the quantity of fruit of cultivars from the other regions. Variance components due to region explained 64% and 26% of the phenotypic variance for early and total yield, respectively, whereas differences among cultivars within regions explained 12% and 7% of the variance for these traits. Cultivars from all regions had significantly larger plants and were more productive when treated with 3 weeks of artificial vernalization. However, region × vernalization effects were nonsignificant for all traits, a result suggesting that selection in Mediterranean environments has not adapted germplasm specifically for low vernalization conditions.

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P. Revilla, V.M. Rodríguez, R.A. Malvar, A. Butrón, and A. Ordás

Four sweet corn (Zea mays L.) heterotic patterns have been reported among sugary1 (su1) open-pollinated cultivars: two among sweet corn cultivars (`Golden Bantam' × `Country Gentleman' and `Golden Bantam' × `Stowell's Evergreen'), one related to the `Reid' × `Lancaster' field corn heterotic pattern (`NE-HY-13A' × `NE-HY-13B'), and one related to the northern × southern Spain field corn heterotic pattern (`EPS31' × `EPS32'). The objective of this research was to compare the performance of sweet corn heterotic patterns. The four crosses and their seven parents were evaluated in 2 years, at two environments in northwestern Spain, as well as in a cold chamber. `Golden Bantam' × `Stowell's Evergreen' and `Golden Bantam' × `Country Gentleman' had poorer agronomic performance and better ear quality than `NE-HY-13A' × `NE-HY-13B' and `EPS31' × `EPS32'. `Golden Bantam' × `Stowell's Evergreen' had the best cold tolerance in the cold chamber. Earliness, emergence, and early vigor were higher for `EPS31' × `EPS32', related to the northern × southern Spain field corn heterotic pattern. Heterosis was positive and significant for several traits for `Golden Bantam' × `Stowell's Evergreen' and `Golden Bantam' × `Country Gentleman,' while heterosis was not significant for `NE-HY-13A' × `NE-HY-13B' and `EPS31' × `EPS32'. The objective of capitalizing on the `Reid' × `Lancaster' and the northern × southern Spain field corn heterotic patterns for improving sweet corn has failed. We believe that heterosis is lost when field corn heterotic patterns are combined with sweet corn, due to incompatibility in gene combination among sweet and field corn genetic backgrounds.

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Ed Kee

Mechanically harvested pickling cucumbers are a once-over destructive harvest system. Gynoecious hybrids are planted at high populations to obtain high yields and to concentrate maturity. Population, row width, plant spacing, and uniform emergence all affect yield and maturity. 65,000 plants/acre in 26 inch rows were found to optimize yield and provide the highest percentage of fruit at the desired uniform size.

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Jonathan P. Lynch and Stephen E. Beebe

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Mary Ruth McDonald*, Kevin Vander Kooi, Cathy Bakker, and Alan McKeown

Globe artichoke (Cynara scolymus L.) is a high value cool season crop which requires vernalization to induce flower formation. The climate in Ontario does not allow for survival of perennial cultivars or for consistent natural vernalization of annuals. Three methods of vernalization were tested: a controlled environment chamber, a lighted cold storage, or GA3 application in the field. Plants, cv. Green Globe Improved, were grown in a greenhouse set at 25 °C day temperature in 72-cell Styro-foam trays in a peat mix. At 4 weeks, plants receiving vernalization were transferred to growth chambers, or lighted coolers (four standard 8 foot cool white fluorescent lamps) at 10 °C for two weeks. The others stayed in the greenhouse. GA3 treatments (PROGIB, 15 g ai/ha) were applied at 2, 4 and 6 weeks after transplanting. Cultivars Green Globe Improved, Imperial Star, Emerald, and Large Green Globe were evaluated in separate trials. Trials were conducted at Simcoe, on coarse sand in a high heat area, and Kettleby, on organic soils in a cooler area of Ontario. Shortly after planting at Simcoe several 30 °C days occurred which devernalized and injured the crop. Artichokes grew well at the Kettleby site. Vernalization in the growth chamber was most effective and resulted in the earliest bud formation and highest total yield (1503 cases/ha). Large Green Globe was not well adapted to Ontario conditions. Imperial Star and Emerald produced the highest yields, 2180 and 1779 cases/ha, respectively. Globe artichokes can be grown successfully as an annual crop in cool production areas of Ontario.

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W.M. Tilson and H.D. Stiles

The analog output of a portable battery-powered infrared pyrometer capable of nondestructive measurement of blackberry fruit temperatures was collected, formatted, and stored by a Polycorder in the field during the 1996 and 1997 harvest seasons. The program written for the data recorder allowed collection of ≈10 temperatures per plot per minute. Download and analysis of the information gathered during a typical survey of 24 rep × treatment combinations was easily completed prior to subsequent surveys in the field at noon and midafternoon.

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J.M.S. Scholberg, B.L. McNeal, J.W. Jones, S.J. Locascio, S.R. Olsen, and C.D. Stanley

Modeling the growth of field-grown tomato (Lycopersicon esculentum Mill.) should assist researchers and commercial growers to outline optimal crop management strategies for specific locations and production systems. A generic crop-growth model (CROPGRO) was previously adapted to simulate the growth of fresh-market tomato under field conditions. Plant growth and development of field-grown tomato, and fruit yields, will be outlined and compared to model predictions for a number of locations in Florida, nitrogen fertilizer rates, and irrigation management practices. Possible application of the model to quantify effects of crop management on crop production will be discussed using simulated yield values for a wide range of environmental conditions.