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Martin L. Kaps and Patrick L. Byers

Fourteen highbush blueberry cultivars are being evaluated in south central Missouri mineral soil. This soil is often not ideal for culture of highbush blueberry. The planting site was initially pH 6.3 with a 92% base saturation on the cation exchange capacity. Sulfur additions, and summer and fall cover cropping were done for 2 years prior to planting to lower soil pH (5.3) and increase organic matter content. Four replications of three plants were set in a randomized complete block in early Apr. 1998. Plant spacing is 1.2 × 3.0 m on bermed rows that are mulched with chipped hardwood. Acidified irrigation water is supplied through drip lines. Fertilizer is applied annually both as dry ammonium sulfate and soluble nitrogen through drip lines at 84 kg·ha-1 N. Cumulative yield per bush after the first five harvest seasons showed `Bluecrop', `Brigitta Blue', `Chandler', `Darrow', `Legacy', `Nelson', and `Reka' at 17 to 21 kg; `Duke', `Nui', `Ozarkblue', and `Sierra' at 14 to 15 kg; and `Collins', `Summit', and `Toro' at 9 to 10 kg. Berry weight averaged 2 g with a low of 1.4 g (`Reka') to a high of 3.3 g (`Chandler'). Plant height averaged 155 cm with a low of 117 cm (`Nui') to a high of 188 cm (`Legacy', `Nelson'). Cultivars in the two higher yield groups were recommended to Missouri growers for planting.

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Thomas J. Zabadal

The effect of cane girdling, in combination with the common commercial practices of gibberellic acid applications and/or other crop control, on vine size and fruit characteristics was measured over 3 years for `Himrod' grapevines (Vitis ×labruscana × V. vinifera) grown in central New York state. Cane girdles 4 mm wide between the second and third node from the base of each fruiting cane resulted in vines that were capable of sustaining vine size while enhancing several aspects of fruit quality. When added to several vine-manipulation regimes, cane girdling increased cluster weight as much as 106%, berries per cluster as much as 138%, and berry weight as much as 17%. Although cane girdling increased yield as much as 66%, it consistently reduced fruit soluble solids concentration (SSC). Therefore, for cane girdling to contribute to sustained production of quality `Himrod' table grapes in a cool-growing-season climate, it will be necessary to practice it in combination with a level of crop control that will ensure acceptable fruit SSC.

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Douglas V. Shaw and Kirk D. Larson

Performance characteristics for eighteen strawberry cultivars (Fragaria ×ananassa), nine from California and nine from other North American sources, were evaluated in annual hill culture, with and without preplant soil fumigation (2 methyl bromide : 1 chloropicrin, 392 kg·ha-1). Plants grown in nonfumigated soil yielded 57% and 46% of the fruit produced by plants on adjacent fumigated soil for cultivars from California and other North American origins, respectively. Plants in nonfumigated soils also developed fruit with lower berry weight (94% and 95% of fumigated trials) and smaller spring plant diameter (83% and 76%) for California and other sources, respectively. Trait values for exotic cultivars ranged from 39% to 80% of those for California cultivars, and the variance component due to germplasm sources explained 41% to 81% of the phenotypic variance of random effects in the experiment. Conversely, significant germplasm source × fumigation interactions were not detected for any of the growth or performance traits evaluated, and the proportion of variance attributable to these interactions was at most 2% of that due to germplasm source. These results demonstrate that strawberry growth and productivity for California and other North American germplasm sources are increased similarly by fumigation. Despite differing selection history, germplasm developed outside of California contains no obvious genetic diversity useful for developing cultivars specifically adapted to the sublethal effects of organisms in nonfumigated soils.

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Imed Dami, Dave Ferree, Anton Prajitna, and Dave Scurlock

`Chambourcin' (Vitis sp.) is a French-American hybrid cultivar that has the propensity to overcrop, and its performance under cool climate and short growing season is not known. This study was conducted for five years (2000 to 2004) to evaluate the effect of three levels of cluster thinning (10, 20, and 30 clusters per vine) on yield and fruit composition of `Chambourcin' grown in northeastern Ohio. Cluster thinning reduced yield per vine and crop load, but increased pruning, cluster and berry weights. Cluster thinning also improved juice composition by increasing soluble solids and pH but not acidity. It was concluded that under the climatic conditions of this study, thinning to 10 clusters per vine (or 8 clusters per meter of row) produced the lowest yield but the highest vine size with the most optimum fruit composition. Therefore, vines from the 10-cluster treatment were considered the most balanced in the 5-year study. Additionally, due to the repeated coincidence of harvest with the first fall frost, it was suggested that the site in continental Northeast Ohio is risky for commercial production and longer and warmer seasons are thus preferred.

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Chrislyn A. Drake and James F. Hancock

Black root rot is a widespread disease of strawberry (Fragaria×ananassa Duchnesne) that causes the death of feeder roots and the degradation of structural roots. The major causal organisms of black root rot include Rhizoctonia fragariae Husain and W.E. McKeen, Pythiumspp. and Pratylenchuspenetrans(Cobb) Filipjev and Schuurmans Stekhoven. The current method of control for black root rot is methyl-bromide fumigation; however, methyl bromide is scheduled to be phased out in 2005, and its effects are short-lived in matted-row systems. The objectives of the study were to measure levels of tolerance to black root rot in 20 strawberry genotypes and to determine which pathogens were present in the soil. The genotypes were planted in four blocks each of methyl-bromide fumigated and nonfumigated soil, and were evaluated for crown number, number of flowers per crown, yield, and average berry weight over two years. The results showed that all three pathogens were present in the field, and that there was a significant genotype × fumigation interaction for yield and crown number in both years. The cultivars Bounty, Cabot, and Cavendish, all released from the breeding program in Nova Scotia, displayed tolerance to the pathogens that cause BRR. Greenhouse studies were conducted using a subset of the genotypes to determine if any one pathogen causes more damage than others, and to determine if susceptibility to a particular pathogen varies between genotypes.

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Andrew G. Reynolds, A.C. Cottrell, D.A. Wardle, and A.P. Gaunce

`Okanagan Riesling' (Vitis spp. parentage unknown) vine trunks treated in 1984 with three levels of NM (0, 10,000, and 20,000 mg·liter-1) and three levels of paclobutrazol (PB; 0, 250, and 500 mg·liter-1, in white latex paint were subjected to a reapplication in June 1987 at the same rates of NAA and at 0, 1000, and 2000 mg PB/liter. Linear reductions in suckers per vine were observed with increasing NAA concentration but not PB. Yield and clusters per vine were reduced by PB in the season following retreatment (1988), while berry weight was increased by NAA in 1987. Titratable acidity was increased by NAA in 1988, and pH was highest that season with PB at 1000 mg·liter-1 . No PB was detected in fruit tissue in 1987, but NAA levels of 2.4 and 2.0 μg·kg-1 were detected in clusters sampled from the 10,000- and 20,000-mg·liter -1 treatments, respectively. Chemical names used: l-naphthaleneacetic acid (NAA); β-1[(4-chlorophenyl)methy]-α-1 (l,l-dimethylethyl)-1H-l,2,4-triazole-l-ethanol (paclobutrazol).

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Teryl R. Roper and J. Klueh

The sources of carbohydrate and other resources for fruit growth in cranberry (Vaccinium macrocarpon Ait.) can be spatially partitioned into new growth, old leaves, and woody stems or other adjoining uprights. This research was conducted to determine which spatial source of resources was most important for fruit set in cranberry. At fruit set in late June, we removed the current season growth, one year old and older leaves, or both from 50 uprights per treatment plus a control at two locations. At harvest, fruit set, fruit number and size were determined. In all cases, removing the current season's growth significantly decreased fruit set. Removing both the current season's growth and old leaves produced an additional reduction in fruit set. Removing only old leaves reduced fruit set at one location but not the other. Fruit length, diameter or mean berry weight was not reduced by any treatment. The response of cranberry to resource limitation apparently is to reduce fruit numbers rather than fruit size. This research suggests that current season growth is the primary source of carbohydrates for fruit set in cranberry and that once the fruit are set they have sufficient sink strength to attract resources from a distance.

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Joseph A. Fiola and Gary C. Pavlis

Downy Mildew, Plasmopara viticola, causes major damage and economic loss to many wine grape cultivars grown in the Northeast. The purpose of the experiment was to test the efficacy of Vossen Blue (VB; iron pigment) in association with fungicides for the control of Downy Mildew disease of wine grapes in New Jersey. The experimental plot was a planting of `Seyval Blanc' (5th leaf). Treatments (applied via back-pack sprayer) included no fungicide (control I), full fungicide (FF) (RCE commercial recs; control II), FF + 4%VB, FF + 8%VB, 8%VB, Half Rate Fungicide (HF) + 4%VB, HF + 8%VB. There were no significant differences between treatments for total yield, average cluster weight, average berry weight, Brix %, and pH. Spectrophotometric (Hunter's Lab) analysis of foliage samples revealed that leaf samples from the VB treatments had greater green color (correlate: increased chlorophyll). Analysis of subjective (1-9) disease incidence data: FF8 significantly lower disease score that FF; FF4, HF4, HF8, and FF no difference. Compared to normal full fungicide: superior Downy Mildew control was achieved by adding VB to full fungicide; equal control was achieved with half fungicide and VB.

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Creighton L. Gupton

Crosses between `Humble' and five other blackberry cultivars were made to determine the efficacy of `Humble' as a source of resistance to rosette (incited by Cercosporella rubi). Seven cultivars and three selections were planted at a disease free location and at a location where rosette is known to occur to determine the effect of double blossom on yield, berry weight, and ripening date. `Cheyenne' X `Humble,' `Humble' X `Brazos,' and `Navaho' X (`Humble' X `Brazos') produced progenies with various levels of resistance. Promising selections were made from the latter two crosses. Genotype X location interaction was significant for yield and not significant for either Julian date of 50% ripe fruit or weight per berry. These results suggest that rosette reduces yield but has little if any effect on weight per berry or ripening date. `Shawnee' and `Choctaw' were the highest yielding cultivars under disease free conditions; however, their yields were low in the test where they were infected with rosette. `Brazos,' `Choctaw,' and `Rosborough' were the earliest ripening and `Navaho' was the latest ripening cultivar.

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John R. Clark and James N. Moore

`Jupiter' is the fifth table grape cultivar released from the Univ. of Arkansas grape breeding program. `Jupiter' originated from a cross of Ark. 1258 × Ark. 1672 made in 1981. The original seedling vine was selected in 1984, and `Jupiter' was tested as Ark. 1985. `Jupiter' was tested at two locations in Arkansas (Fayetteville and Clarksville) and at West Lafayette, Ind. Fruit of `Jupiter' are reddish-blue, and berry weight averaged 5.5 g over 12 years of evaluation at Clarksville. Fruit are seedless, have a non-slipskin texture, ripen early mid-season, and averaged 19.8% soluble solids. Flavor is a mild muscat, a noteworthy character of this new cultivar. Clusters averaged 257 g over 12 years and are well-filled. Yields of `Jupiter' have been very good, exceeding 29 t/ha at Clarksville. Hardiness of `Jupiter' was greater than `Einset Seedless', `Himrod', or `Vanessa Seedless', but less than `Mars' or `Reliance' at West Lafayette. `Jupiter' is recommended for trial where other other eastern U.S. table grape cultivars are adapted.