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Laurie E. Boyden* and Peter Cousins

Development of rootstocks resistant to root-knot nematodes (Meloidogyne spp.) is a priority in grape breeding. The N allele, present in Harmony and Freedom rootstocks, confers resistance to N-avirulent strains of Meloidogyne. Extensive planting of rootstocks containing N has led to the development of N-virulent nematode strains, prompting a search for new resistance alleles. A seedling population derived from Vitis nesbittiana Comeaux was evaluated to investigate the genetic control of nematode resistance in this species. Hybridization with easily propagated rootstock selections will be required to utilize nematode resistance found in V. nesbittiana, a native of Mexico. The female parent of the population was 161-49C, a V. riparia × V. berlandieri hybrid rootstock. 161-49C does not contribute nematode resistance to its progeny. The male parent was V. nesbittiana DVIT 2236.12, an accession held in the U.S. National Plant Germplasm system. Nematode resistance of the 161-49C × V. nesbittiana DVIT 2236.12 population was assessed in greenhouse pot culture. Seedling roots were stained in an eosin-Y solution six weeks after inoculation with 1500 N-virulent M. arenaria juveniles. Resistance classes of seedlings were determined by assessing the degree of galling and number of egg masses per root system. Segregation in the seedling population was consistent with a 1:1 ratio of resistance to susceptibility, indicating that the V. nesbittiana accession is heterozygous for a dominant allele conferring resistance to N-virulent root-knot nematodes. The genetic relationship between this allele and the N allele has yet to be determined.

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Brandon Smith* and Lailiang Cheng

One-year-old `Concord' grapevines (Vitis labrusca L.) were fertigated twice weekly for 11 weeks with a complete nutrient solution containing 1, 10, 20, 50 or 100 μmol iron (Fe) from ferric ethylenediamine di (o-hydroxyphenylacetic) acid (Fe-EDDHA). Leaf total Fe content did not increase in response to Fe supply, however both “active” Fe (extracted with 2, 2'-dipyridyl) and chlorophyll (Chl) content increased as applied Fe increased. At the lowest active Fe level, leaf absorptance and maximum PSII efficiency (Fv/Fm) were slightly decreased, and non-photochemical quenching was significantly greater. PSII quantum efficiency decreased curvilinearly as active Fe content decreased. On a Chl basis, the xanthophyll cycle pool size, lutein, and beta-carotene increased curvilinearly as active Fe decreased, and neoxanthin increased at the lowest Fe level. Activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase followed a similar trend and increased under Fe deficiency, when expressed on a Chl basis. Antioxidant metabolites also increased in response to Fe limitation. On a Chl basis, ascorbate (AsA), dehydroascorbate (DAsA), reduced glutathione (GSH) and oxidized glutathione (GSSG) content was greater at the lowest active Fe levels. We did not find a difference in the ratio of AsA to DAsA or GSH to GSSG. In conclusion, both photoprotective mechanisms, xanthophyll cyle-dependent thermal dissipation and the ascorbate-glutatione antioxidant system, are enhanced in response to iron deficiency to cope with excess absorbed light.

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M. Dolores Loureiro, M. Carmen Martínez, Jean-Michel Boursiquot, and Patrice This

`Albariño' (Vitis vinifera L.) is an important grape cultivar in Spain, morphologically diverse but subject to much misnaming. The objectives of the present work were to correct some of the more common misnamings concerning `Albariño' and to evaluate the genetic variability within this cultivar by analyzing DNA polymorphisms using randomly amplified polymorphic DNA (RAPD) markers and microsatellite techniques. Several accessions of `Albariño' (16 accessions from Misión Biológica de Galicia, one accession from El Encin, one accession from Rancho de la Merced), related cultivars (`Alvarinho', `Caíño blanco', `Cainho branco', `Loureiro'), and cultivars presumably identical to misnomers (`Savagnin blanc' and `Gewürztraminer') were analyzed using 20 RAPD markers and six microsatellite loci. Both techniques revealed polymorphism among `Albariño', `Caíño blanco', `Albariño' from Rancho de la Merced and `Loureiro'. No polymorphism was detected among the 16 `Albariño' accessions from Galicia, the `Albariño' accession from El Encin and `Alvarinho', nor among the `Albariño' accession from Rancho de la Merced, `Savagnin blanc' and `Gewürztraminer', nor between `Caíño blanco' and `Cainho branco'. These results enabled us to clarify the main misnomers concerning these cultivars. The absence of polymorphism among the true `Albariño' accessions did not allow the detection of any clonal variation. The suitability of both techniques for defining the cultivar level for grapevine is discussed.

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Andrew G. Reynolds, Douglas A. Wardle, and Marjorie Dever

Vitis vinifera L. cultivars Müller-Thurgau, Muscat Ottonel, Gewürztraminer, and Kerner were studied for 1 year to document changes in fruit terpene levels from berry stage to free-run and press-juice stages. Substantial amounts of free volatile terpenes (FVTs) and potentially volatile terpenes (PVTs) were lost between berry and juice stages. PVTs were higher in press juices of `Gewürztraminer' and `Muscat Ottonel' than in free-run juices. In another experiment, juices from `Miiller-Thurgau', `Muscat Ottonel', `Kerner', `Optima', `Pearl of Csaba', and `Siegerrebe', harvested 10 to 20 days after a designated initial harvest date, contained higher FVTs and PVTs than initially. A third experiment with `Kerner', `Müller-Thurgau', `Optima', and `Siegerrebe' found highest FVTs and PVTs in juices from grapes subjected to skin contact compared with grapes crushed and immediately pressed. Sensory evaluation showed aroma differences between wines from free-run and press juices of `Miiller-Thurgau' and `Muscat Ottonel', aroma and flavor differences due to harvest date for all cultivars except `Pearl of Csaba', and aroma and flavor differences due to skin contact for `Siegerrebe'.

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Peter C. Andersen and Charles A. Sims

The influence of bilateral cordon (BC) and cane training systems and level of pruning severity on vegetative and reproductive characteristics of Vitis hybrid `Suwannee' were determined from 1987 to 1989. In 1987, yield and quality were similar on BC- and cane-trained vines. In 1988, shoot count, yield, and quality were similar regardless of training system and pruning severity (50, 70, or 90 nodes per vine). When data from both training systems were combined, yield was related to the number of shoots. Vines pruned more severely compensated by producing more shoots from non-count (non-node) positions on the canes, cordon, or spurs. Similarly, in 1989 yield and berry quality were not affected by training system or levels of pruning severity (50, 70, 90, or 110 nodes), although berry weight was affected by training system, and shoot count and shoot length were affected by level of pruning severity. Interactive effects of training system and pruning level were not significant in either year. An analysis of combined data for 1989 indicated that yield was affected by the number of nodes and shoots. Thus, `Suwannee' may be trained to the BC system, which is more readily adapted to mechanization. Pruning to a specific number of nodes per vine was not critical.

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Sudarsono and Ronald G. Goldy

Four muscadine grape (Vitis rotundifolia Michx.) cultivars (Carlos, Noble, Regale, and Tarheel) were evaluated for their ability to be cultured in vitro. Axillary buds were placed on Murashige and Skoog medium as modified by Chee. Different levels of benzylaminopurine [(BA) 0.5 to 10.0 μm], kinetin [(KIN) 0.5 to 5.0 μm], and thidiazuron [(TDZ) 0.5 to 11.3 μm], and different explant positions were evaluated for their effect on in vitro explant establishment and shoot production. Thidiazuron (2.3 to 4.5 μm) alone or in combination with BA (1.0 to 5.0 μm) or KIN (1.0 or 5.0 μm) was effective for establishing axillary buds. Similar levels were also effective for promoting shoot proliferation. Explants originating from the 10 basal nodes of a shoot with at least 25 nodes gave better shoot proliferation than explants originating from the 10 distal nodes. Chemical names used: 6-benzylaminopurine, 6-furfurylaminopu. rine (kinetin):N -phenyl-N'-l,2,3 -thiadiazol-5-y lurea (thidiazuron).

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Zhongbo Ren and Jiang Lu

Non-native grape species such as V. vinifera and V. labrusca can not sustain the hot and humid environment of Florida due to their susceptibility to various diseases. Vitis rotundifolia (muscadine grapes) is native to Florida and the southeastern United States and adapted well to this climate condition. They are highly resistant to almost all grape foliage diseases and root pests such as nematode and phylloxera. Theoretically, muscadine grapes may become a valuable rootstock for bunch grapes. Unfortunately, most previous studies found that muscadine grapes were graft-incompatible with bunch grapes by normal grafting techniques. This study was to look for an alternative technique to graft V. vinifera onto muscadine rootstocks. A preliminary study indicated that bunch grape scions were successfully grafted on adult muscadine grapes. Two V. vinifera grape cultivars, `Thompson Seedless' and `Chardonnay', and two muscadine grape cultivars, `Carlos' and `Alachua', were used for this study. The muscadine grapes used as rootstocks are 6-year old field-grown vines and V. vinifera was used as scions. Using the common V-type grafting method was completely failed in more than 150 attempts. We then tried to insert the first-year buds of V. vinifera into 1- to 3-year-old muscadine canes. Surprisingly, the survival rate of the inserting buds was moderately high when `Carlos' was used as the rootstock. `Thompson Seedless'/`Carlos', `Chardonnay'/`Carlos' reached 53% and 33%, respectively. Successful grafting but lower survival rate was also obtained when `Alachua' was used as the rootstock (10% in `Thompson Seedless/`Alachua' and 3% in `Chardonny'/`Alachua'). The average survival rate of `Thompson Seedless' on the muscadine rootstocks was 36%, and `Chardonnay' was 12%. Regardless the cultivar of the scions, buds survived on `Carlos' and `Alachua' rootstocks were 44% and 5%, respectively. Results from this study indicated that V. vinifera grapes could be successfully grafted onto muscadine rootstocks. The survival rate varied depending on cultivars used for both scion and rootstock. It would be very interesting to see if resistance to certain diseases such as the Pierce's disease can be improved in those V. vinifera grape with muscadine roots and trunks derived from this preliminary study.

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M. Padgett-Johnson, L.E. Williams, and M.A. Walker

A comparison was made among 16 native North American Vitis species and Vitis vinifera L. ('Carignane') grown in the San Joaquin Valley of California with or without irrigation over 2 years. Predawn water potential (ΨPD), predawn leaf osmotic potential (Ψπ), midday leaf (Ψl), and stem water potential (Ψstem), stomatal conductance (gs), net CO2 assimilation rate (A), and intrinsic water use efficiency (WUE) were measured on five dates during the growing season the first year of the study and pruning weights were evaluated both years. Net gas exchange and water potential components taken on the last measurement date in 1992 and pruning weights of the nonirrigated species were less (or more negative for Ψ components) than those of the irrigated vines. The 17 Vitis species were ranked according to their relative drought tolerance based upon their performance without irrigation and when compared to their irrigated cohort. The Vitis species considered most drought tolerant were V. californica, V. champinii, V. doaniana, V. longii, V. girdiana, and V. arizonica. Those six species generally had high values of A, gs, and pruning weights and more favorable vine water status at the end of the study than the other species when grown without irrigation. The drought-induced reductions in the measured parameters also were less for those species when compared to their irrigated cohorts. The least drought tolerant species were, V. berlandieri, V. cinerea, V. lincecumii, V. riparia, and V. solonis. The drought-tolerant rankings were generally associated with the species' native habitat and probable soil water availability.

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Summaira Riaz, Keith E. Garrison, Gerald S. Dangl, Jean-Michel Boursiquot, and Carole P. Meredith

In total, 25 clones of Vitis vinifera `Pinot noir' and 22 clones of `Chardonnay' were analyzed with 100 microsatellite markers, selected from an initial screening of 228 markers. Of the 100 markers, 17 detected polymorphism within one or both of the cultivars. In `Pinot noir', 15 polymorphic markers detected 15 different genotypes, uniquely distinguished 12 clones out of the 25 and separated the remaining 13 clones into 3 groups. In `Chardonnay', 9 polymorphic markers detected 9 genotypes and uniquely distinguished 6 clones out of the 22. The remaining 16 clones were separated into 3 groups. For markers that were polymorphic in `Pinot noir' and `Chardonnay', none of the variant alleles were common to both cultivars. It is inferred from this result that the natural cross that produced `Chardonnay' probably occurred when `Pinot' was still relatively young. Many of the variant genotypes were expressed as three alleles. Further analysis revealed the presence of chimeras in which the third allele was present in leaf but not root or wood tissues, confirming that the grape apical meristem is functionally two-layered. Some clones that share the same microsatellite genotype are documented to have originated in the same locality, suggesting that the origins of undocumented clones may be traced by comparing their microsatellite genotypes with those of well-documented clones. Because clones of `Pinot noir' and `Chardonnay' are often visually indistinguishable, microsatellite genotyping may also be useful to detect identification errors in collections and nurseries.

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John Fitzgerald and W. Keith Patterson

Canopy management and ethephon application (100 mg·liter-1 2 weeks after veraison) were investigated for 2 years as possible ways to improve color and overall quality of `Reliance' grapes (Vitis spp.). Canopy management consisted of leaf removal, shoot positioning, and cluster thinning. Grapevines were subjected to one of two levels of leaf removal and one of two levels of preharvest ethephon spray and were either thinned to a basal cluster or nonthinned. Thinning and ethephon advanced harvest dates by 5 to 8 days and 2 to 3 days, respectively. In 1989, berry weight was increased by thinning but was not affected by leaf removal or ethephon. Leaf removal (direct sun exposure) of thinned and nonthinned treatments increased “L” values (lighter colored fruit) in 1989. In 1990, leaf removal, ethephon, and thinning resulted in higher “L” values. The “a” values were significantly increased by leaf removal in 1989 and 1990 and by thinning in 1989, a result indicating increased skin redness. Exposed clusters of nonthinned treatments had significantly higher “b” values due to more yellow fruit in 1989 than in 1990. Ethephon increased “b” values in thinned and nonthinned treatments. In 1990, leaf removal increased “b” values. Thinning resulted in more evenly colored, redder fruit. Leaf removal caused a lightening and yellowing of the skin. Juice from leaf removal treatments in 1990 had significantly higher “L”, “a”, and “b” values. Ethephon significantly increased the “a” value of juice in 1989, and leaf removal significantly increased the “b” value in 1989. The percent soluble solids of juice was generally decreased by ethephon and increased by leaf removal and thinning. Titratable acidity was decreased by leaf removal and ethephon and increased by thinning in both years. Leaf removal decreased berry pH in 1990. Thinning increased coloration, and direct exposure to light decreased coloration. The results with ethephon were not conclusive. Chemical name used: 2-chloro-ethyl-phosphonic acid (ethephon).