Grape Species Research Articles

Ochratoxin A and ochratoxigenic Aspergillus species in Argentinean wine grapes cultivated under organic and non-organic systems

The evolution of contamination with Aspergillus section Nigri and ochratoxin A occurrence was evaluated in four vineyards located at Mendoza province, Argentina during 2003–2004. The survey included two grape varieties, one of late maturation (Bonarda) and the other of early maturation (Tempranillo). The vineyards were set under non-organic and organic cropping systems. Bunches of grapes at different growth stages were collected, and berries (50 by sample) were plated on Petri dishes containing Dichloran 18% Glycerol Agar (DG18) and Dichloran Rose Bengal Chloramphenicol Agar (DRBC) media. After an incubation period of 7 days at 25 °C ± 1 °C, the mycoflora belonging to Aspergillus section Nigri was identified. The ability to produce ochratoxin A (OTA) by the potential ochratoxigenic species was evaluated on YES (2% yeast extract, 15% sucrose) medium. The cultures were incubated at 30 °C ± 1 °C for 10 days in darkness. The OTA content of the grapes was determined by HPLC. Through the different growth stages, from setting to harvest, grape contamination by the Aspergillus species, section Nigri increased. The main species isolated belonged to the A. niger aggregate. From 246 strains evaluated 24% was ochratoxigenic. OTA was not detected in grapes during the survey.

Thermostability of Photosynthesis of Vitis aestivalis and V. vinifera

High temperature adversely affects photosynthetic rates and thylakoid activities in many species, but photosynthesis response to heat stress is not well defined in grapes (Vitis L.). Genotypes within species respond differently to high temperatures, indicating a genetic variability for the trait. The objective of this study was to determine the physiological responses of two grape species to high temperature, at the whole-plant level and at the cellular level. Gas exchange, relative chlorophyll content, and chlorophyll fluorescence of intact leaves and thermostability of extracted thylakoids of the American (V. aestivalis Michx.) `Cynthiana' and European (V. vinifera L.) `Semillon', `Pinot Noir', `Chardonnay', and `Cabernet Sauvignon' wine grapes were evaluated. One-year-old vines were placed in controlled environmental chamber held at 20/15, 30/25, or 40/35 °C day/night for 4 weeks. Net CO2 assimilation (A) rate, stomatal conductance (gs), transpiration (E) rate, chlorophyll content, and chlorophyll fluorescence of intact leaves were measured at weekly intervals. Chlorophyll fluorescence of thylakoids extracted from V. aestivalis `Cynthiana' and V. vinifera `Pinot Noir' subjected to temperatures ranging from 20 to 50 °C was measured. Optimal temperatures for photosynthesis were 20/15 °C for `Cynthiana' and `Semillon' and 30/25 °C for the other three V. vinifera cultivars. The A, gs, E, chlorophyll content, and chlorophyll fluorescence values at 40/35 °C were lower in `Cynthiana' than `Pinot Noir'. In general, reduction of A coincided with decline in gs in `Cynthiana', whereas no strong relationship between A and gs was observed in V. vinifera cultivars. Variable chlorophyll fluorescence (Fv) and the quantum efficiency of photosystem II (Fv/Fm) of intact leaves for all the cultivars decreased at 40/35 °C, with severe decline in `Cynthiana' and `Cabernet Sauvignon,' moderate decline in `Semillon' and `Chardonnay', and slight decline in `Pinot Noir'. A distinct effect of high temperature on Fv and Fv/Fm of `Cynthiana' was exerted after 2 weeks of exposure. Prolonged-exposure to 40/35 °C led to 78% decrease in Fv/Fm in `Cynthiana', compared with 8% decrease in `Pinot Noir'. In general, Fv and Fv/Fm of extracted thylakoids declined as temperature increased, with more decline in `Cynthiana' than in `Pinot Noir'. Based on A rates and Fv/Fm ratios, results showed that `Cynthiana' has lower optimal temperature for photosynthesis (20/15 °C) than `Pinot Noir' (30/25 °C). Chlorophyll fluorescence responses of intact leaves and extracted thylakoids to high temperatures indicate that `Pinot Noir' possess higher photosynthetic activity than `Cynthiana'. Results of this work could be used in selection programs for the development of heat resistant cultivars in the warmest regions.

Resistance to Pierce’s Disease inMuscadinia rotundifoliaand Other Native Grape Species

Pierce’s disease (PD), caused by the bacterium <i>Xylella fastidiosa</i>, is a major disease of grapevines. Grape species native to southern areas of North America where the disease is severe have evolved resistance to PD. Using controlled greenhouse trials, a quantitative assessment of the level of resistance in cultivated and wild selections of five native grape species was made. Conclusions were based on estimates of bacterial concentrations in stem tissue via ELISA and subjective evaluations of disease symptoms. <i>Vitis labrusca,</i> native to the northeast United States where PD is absent, appears to be as susceptible as <i>Vitis vinifera</i>. California natives <i>Vitis californica</i> and <i>Vitis girdiana</i> appear to be moderately susceptible, although there was significant variation among the <i>V. girdiana</i> selections. In contrast, <i>Muscadinia rotundifolia</i> and <i>Vitis arizonica</i>, both native to areas of severe disease pressure, appear to be very resistant. A pattern of resistance correlating with geographic variation in disease pressure was also evident within species. Wild accessions of <i>M. rotundifolia</i> from cooler areas such as Tennessee, where PD is uncommon, supported up to 20x higher concentrations of bacteria than the accessions from Florida where PD is severe. Trials with wild accessions of <i>V. girdiana</i> showed a similar pattern, with susceptible selections supporting up to 100x higher bacterial concentrations. Results demonstrated a gradient of resistance both among and within species, consistent with the hypothesis that PD resistance has evolved in response to disease pressure. This study identifies candidate plant material for breeding projects and provides insight into the genetic and physiological basis of PD resistance in native grapes.

TRI-TROPHIC INTERACTIONS AMONG GRAPEVINES, A FUNGAL PATHOGEN, AND A MYCOPHAGOUS MITE

Grapevines are grown commercially in many parts of the world. The biotrophic pathogen of grapevine and causal agent of grapevine powdery mildew (Uncinula necator) is likewise distributed, and a serious constraint on production. We discovered in previous work that a tydeid mite (Orthotydeus lambi) suppressed U. necator on riverbank grapevine (Vitis riparia). In the present study, we quantified the direct and interactive effects among the host plant, pathogen, and mite. We planted 15 grape genotypes selected from three Vitis species, plus interspecific hybrids, in a common garden. The genotypes displayed significant variation in a morphological trait known to influence mite population densities: the size of domatia, the tufts of nonglandular trichomes at vein axils of the abaxial leaf surface. Vines were either experimentally infested with O. lambi (“release” vines) or kept free of mites. Over a four-year period we quantified the severity of powdery mildew on foliage as well as the density of O. lambi. In the absence of O. lambi, disease severity was highest among genotypes of the European grape species V. vinifera. Susceptibility varied from high to moderate among Vitis interspecific hybrids, while genotypes from the native North American species, V. riparia and V. labrusca, were generally resistant. O. lambi successfully established on release vines quickly, achieving densities similar to those found on wild V. riparia one year after release. O. lambi significantly suppressed foliar disease for genotypes of all grape species, although the magnitude of suppression varied. Moreover, there was a significant effect of grape species and grape genotype on O. lambi abundance that was positively correlated with the size of domatia. In some years, the positive association between domatia size and density of O. lambi translated into less severe foliar disease, after controlling for differences in inherent resistance. Although the importance of host-plant genetics and abiotic environmental factors in plant disease is well recognized, this study shows that natural enemies of pathogenic fungi, and their interactions with the host plant, can play a significant role. A more complete understanding of the complex interactions within this system may enhance the efficacy of mycophagous mites as biological agents for powdery mildew.

Oxygen radical absorbance capacities of grape/wine industry byproducts and effect of solvent type on extraction of grape seed polyphenols

Grape seed powders, byproducts of either winemaking or grape processing, were prepared from Vitis vinifera (Merlot and Chardonnay) and Vitis rotundifolia (Muscadine) species. Water, methanol, acetone and ethanol were tested as extractants on Muscadine seed powder. Antioxidant activities of grape seeds and skins were determined as oxygen radical absorbance capacity with phycoerythrin (ORAC PE) for both grape species. The results indicated that aqueous solutions of ethanol, methanol or acetone were better than a single-compound solvent system for extraction of total phenols from Muscadine seed powder. Antioxidant capacities of Chardonnay, Merlot and Muscadine grape seeds were 638, 345 and 311 μmol Trolox equivalent (TE)/g dry weight in decreasing order ( P < 0.05 ) , respectively. (ORAC PE) values of Chardonnay and Merlot grape skin powders were similar. Total phenol contents of extracts used to determine the antioxidant capacities of grape seeds and skins had a trend similar to (ORAC PE) values. Our results showed that health functional components of grape skin and seed powders from the tested byproducts of grape/wine industry are comparable to those of fruits and vegetables.

Correlation between Glassy-winged Sharp Shooter Feeding Preference and Pierce's Disease Development on Grapevines

Although some of the American native Vitis species and their hybrids, particularly those originated from the southeastern United States, have been known for resistance to Pierce's disease (PD), their resistant status against the glassy-winged sharp shooter [GWSS, Homalodisca coagulata (Say)], the vector transmitting PD pathogen (Xylellafastidiosa Well), has not been reported. To determine GWSS feeding preferences on different grape species/cultivars and correlations of feeding to Pierce's disease development, a survey was conducted at Florida A&amp;M University, Tallahassee. The feeding preference of GWSS on different species/cultivars was evaluated in two different ways: 1) count the number of GWSS on different grapevines in the field; and 2) determine the feeding preference by measuring the excretion of the GWSS feeding on difference grape species/cultivars, including highly susceptible V. vinifera cultivars, native American grape species and hybrids, and muscadine grapes. Results from this study indicated that the frequency of GWSS visits on different grapevines varied among the species/cultivars investigated. For example, PD-resistant grape V. rotundifolia (muscadine grape) had significantly fewer GWSS visits than did the PD-susceptible V. vinifera grape. The frequency of GWSS visits to V. labrusca, the native American grape susceptible to PD, was intermediate between those found on V. rotundifolia and V. vinifera. Similarly, the GWSS sucked more xylem sap when they fed on PD-susceptible grapevines than on PD-resistant ones. Overall, there is a positive correlation between the GWSS visits/feeding and the status of grapevine resistance/susceptibility to Pierce's disease.

Ochratoxin A-producing species in grapes and sun-dried grapes and their relation to ecophysiological factors

To explain the dominance of OTA-producing fungal species in sun-dried grapes for special wine production through an ecophysiological approach. Grapes at different ripening stages, sun-dried grapes and raisins were analysed for fungal presence, and isolates identified. Aspergillus section Nigri incidence in grapes increased with grape maturation. In the ecophysiological study five isolates (Alternaria alternata, Cladosporium herbarum, Penicillium decumbens, Aspergillus carbonarius, A. niger aggregate and A. section Nigri uniseriate) were inoculated in SNM medium at four a(w) (0.82-0.97) and incubated at 20, 30 and 40 degrees C for 18 d. Isolates were also inoculated in pairs to evaluate fungal interactions recording their growth rates and indexes of dominance. Aspergillus section Nigri grew in a wider range of temperature and a(w), had higher growth rates than the others under most of the conditions tested and showed behaviour usually dominant. The presence of A. section Nigri is predominant in grapes during harvesting and sun-drying period likely because of a better adaptation to hot and humid environment. The duration of the drying period should be reduced as much as possible without compromising the quality of the final product, or drying the grapes in controlled chambers with dry hot air flow.

Preliminary Pathogenesis-relative Pathways Network Analysis and Relative Putative Genes Annotation In Vitis shuttleworthii Grape through EST Analysis

Vitis shuttleworthii is one of the most disease and pest resistant grape species originated and distributed in the southeast United States. It is highly resistant to Pierce's disease, anthracnose, black rot and downy mildew diseases, which are the limited factors to grow Vitis vinifera grapes in this region. A V. shuttleworthii cDNA library was constructed with mRNA isolated from leaves and flowers harvested during anthesis. 12,008 clean EST sequences were obtained and assembled. and generated 5776 unigenes 2106 contigs and 3670 singletons). ESTs distribution based on protein function using a modified MIPS MATDB Arabidopsis Scheme revealed that 7% of the V. shuttleworthii ESTs were related to disease/pest defense or stress tolerance genes. Over 300 contigs containing complete or 90% open coding region of known functional genes were obtained. The ESTs that were annotated as pathogenesis-related proteins, enzymes in salicylic acid, jasmonic acid, and ethylene signaling, were selected for further study in order to elucidate the role and interaction of them in the signal transduction cascade that leads to grape defense gene activation upon treatment of bacterial pathogen. We report the identification of novel disease resistant genes based on preliminary pathogenesis-relative pathways network analysis.

PCR Assay for Identification of Aspergillus Carbonarius and Aspergillus Japonicus

Black Aspergilli, and in particular Aspergillus carbonarius, are the main causes of contamination of grapes and their by-products by ochratoxin A. A PCR-based method was developed to detect DNA of A. carbonarius and A. japonicus. Two pairs of primers (CARBO1/2 and JAPO1/2) designed from the calmodulin gene, produced PCR products of 371 and 583 bp for A. carbonarius and A. japonicus, respectively. Primer specificity was tested with DNA of 107 strains belonging to Aspergillus section Nigri isolated mostly from grapes in Europe. The sensitivity of primers CARBO1/2 and JAPO1/2 was 12.5 pg when using pure total genomic DNA of the two species. The developed primers provide a powerful tool for detection of the main ochratoxigenic producing Aspergillus species in grapes.

Handling, Storage and Postharvest Physiology of Muscadine Grapes

Abstract General principles pertaining to the regulation of temperature, relative humidity, and modified or controlled atmosphere conditions for maintaining the quality of fruits and vegetables during storage and transit can be applied to muscadine grapes. Muscadine grapes (Vitis rotundifoliaMichx.) are grown primarily in the southern United States and differ from other grape species and hybrids in that their berries are borne in small clusters of 3 to 10 berries and detach from their pedicels when ripe. In general high quality muscadines are free of injury, decay, and sunscald, appear and feel turgid, have a dry stem scar, and are fully bronze or black in color.

The inheritances of fruit skin and must colors in a series of interspecific and intraspecific crosses between V. vinifera and the wild grape species native to China

A total of 1015 seedlings, obtained by 11 interspecific crosses between Chinese wild grapes and V. vinifera, five intraspecific crosses of V. vinifera and one intraspecific cross of V. romanetii were grown in a vineyard of Northwestern Agricultural University for 10 years. Fruit skin color, must color and ionic anthocyanin (IA) concentration of berry skin were evaluated. Color of berry skin was governed by two gene pairs. Clones’ skin color genotypes were deduced according to hybrids segregation ratio. Inheritances of must color and IA content were also investigated. Poor relationships were found between skin, must color and IA concentration. The results demonstrated that clones’ fruit color and IA content could be predicted according to parental genotype in grape crossbreeding. The results would be important to breed new grape cultivars with different colors using the valuable wild grapes native to China as parents.

English

&nbsp; European (Vitis vinifera) and American (Vitis labrusca) grape species succumb to a bacterial disease known as Pierce&rsquo;s Disease (PD). In contrast, muscadine grape genotypes (Vitis rotundifolia) are tolerant/resistant to PD. This is due to the unique biochemical composition of muscadine xylem.&nbsp; However, because of low protein concentration, conventional methods such as low-pressure chromatography and PAGE are unsuitable for grape xylem protein characterization.&nbsp; In addition, these procedures are tedious, time-consuming and require large amount of sample.&nbsp; This study reports a procedure for isolating and separating proteins from muscadine and bunch grape xylem tissue. The procedure consists of separation of xylem from cortex and phloem, removal of pigments and other gummy substances from xylem with ethanol: ethylacetate (2:1) and subsequent Capillary Electrophoretic (CE) analysis of xylem protein extracts to achieve desired resolution.&nbsp; Number of peaks, peak height and areas, retention time and baseline position were used to compare resolution and study the effect of sample and separation buffer.&nbsp;&nbsp;Xylem tissue proteins extracted with 0.05% sodium borate buffer (pH 8.3) and subjected to CE using 1.2% sodium borate (pH 8.3) as a separation buffer were found to yield most satisfactory resolution of grape xylem proteins.&nbsp; The data obtained by CE were consistent and reproducible, and hence, is well suited to obtain excellent resolution of xylem tissue protein for identifying differences in protein composition among the grape genotypes. Key words:&nbsp; Capillary electrophoresis, grape,&nbsp;Vitis, xylem, Pierce&rsquo;s disease, protein.

The arrest of development of abortive reproductive organs in the unisexual flower of Vitis vinifera ssp. silvestris

During the first stages of development, flowers of most dioecious species are hermaphroditic, with their transition to unisexual flowers being the result of the developmental arrest of one set of reproductive organs. In this work, we describe the development of male and female flowers of the dioecious wild grape species Vitis vinifera ssp. silvestris through scanning electron microscopy analysis and cytological observations, focusing our attention on the transition from bisexual to unisexual development. We divide floral development of the wild grape into eight stages. Differences between male and female flowers appear first at stage 6, when the style and stigma start to differentiate in female but not in male flowers. Cytological analysis of the slowly growing abortive pistil of male flowers shows that megagametophyte formation is, surprisingly, not inhibited. Instead of pistil abortion in the male flower, sexual determination is accomplished through programmed death of external nucellus cells and some layers of integumentary cells. Sterility of male structures in female flowers follows a different pattern, with microspore abnormalities evident from the time of their release from the tetrad. Sterile microspores and pollen grains in female flowers display an abnormal round shape, lacking colpi and possessing uniformly thickened cell walls that impede germination.

Selecting in situ conservation sites for grape genetic resources in the USA

Previously, there has not been any in situ conservation sites for crop germplasm within the United States Department of Agriculture (USDA), Agricultural Research Service (ARS), National Plant Germplasm System (NPGS). Using morphologic and molecular (SSR markers) techniques, we assessed the genetic variation present in populations of rock grape (Vitis rupestris Scheele), a native American grape species, throughout its range. We identified seven in situ conservation sites for rock grape using a strategy based on morphologic and molecular data, taxonomic information, population size and integrity, and landholder commitment. In collaboration with federal and state landholding agencies, we have established the first NPGS in situ conservation sites for American wild relatives of a crop.

Locating the sources of an invasive pest, grape phylloxera, using a mitochondrial DNA gene genealogy.

Range expansions through human introductions have increased with global commerce and have led to the extinction of native species, alterations in community structure and pest status of the invasive species. Inferring the evolutionary history of invasive species can help to build a firmer footing for management tactics. This study used mitochondrial DNA (mtDNA) sequence comparisons of samples collected from the native and introduced ranges of a pest herbivore of cultivated grapes, grape phylloxera (Daktulosphaira vitifoliae Fitch, Phylloxeridae) to infer the sources and pattern of introductions into worldwide viticulture. Introductions into viticulture from its native North American range first occurred in the mid-19th century. The pattern of spread has suggested a focus of introduction into France, but independent introductions may have occurred elsewhere. The results show that the introduced population represents a limited subsample of the native genetic diversity. The data suggest that most grape phylloxera in viticulture, including all European, have originated in the northeastern USA where the grape species Vitis riparia dominates. There was evidence for independent introductions into South Africa and California. Most California haplotypes were most closely related to native grape phylloxera from the Atlantic Coast on V. vulpina. It is likely that subsequent spread from California into Australia, New Zealand and Peru has occurred.

Resistance gene analogs are candidate markers for disease-resistance genes in grape ( Vitis spp.).

A set of NBS-containing sequences was isolated from genomic DNA of two grape species ( Vitis amurensis and Vitis riparia) and characterised in a panel of Vitis genotypes carrying different levels of resistance against downy mildew and other diseases. A PCR-mediated approach made use of degenerate primers designed on conserved regions encoding known R-genes, and provided the source for cloning grape analogous sequences. Cloned sequences were digested with ten endonucleases and 29 out of 71 putative recombinant clones, which showed unique restriction patterns, were sequenced. Using a threshold value of 40% identity, at least 12 grape NBS-sequences had a high overall similarity with known R-genes, such as the Arabidopsis gene RPS5 and the tobacco gene N. The presence of internal conserved motifs provided evidence that sequences isolated from grape may belong to the NBS-LRR gene family. A cluster analysis based on the deduced amino acid sequence and carried out on grape NBS-sequences, together with several analogous domains of known R-genes, classified grape sequences into three major groups. A grape sequence of each group was used as a probe on Southern blots with digested genomic DNA from resistant and susceptible grapes. One of the NBS-containing probes showed a clear-cut separation between resistant species and susceptible varieties. This evidence makes the probe a candidate marker for disease resistance genes in Vitis germplasm.

Identification of resistance gene analogs linked to a powdery mildew resistance locus in grapevine.

Oligonucleotide primers, designed to conserved regions of nucleotide binding site (NBS) motifs within previously cloned pathogen resistance genes, were used to amplify resistance gene analogs (RGAs) from grapevine. Twenty eight unique grapevine RGA sequences were identified and subdivided into 22 groups on the basis of nucleic acid sequence-identity of approximately 70% or greater. Representatives from each group were used in a bulked segregant analysis strategy to screen for restriction fragment length polymorphisms linked to the powdery mildew resistance locus, Run1, introgressed into Vitis vinifera L. from the wild grape species Muscadinia rotundifolia. Three RGA markers were found to be tightly linked to the Run1 locus. Of these markers, two (GLP1-12 and MHD145) cosegregated with the resistance phenotype in 167 progeny tested, whereas the third marker (MHD98) was mapped to a position 2.4 cM from the Run1 locus. The results demonstrate the usefulness of RGA sequences, when used in combination with bulked segregant analysis, to rapidly generate markers tightly linked to resistance loci in crop species.

A METHOD FOR EVALUATION AND STANDARDIZATION OF OLIGOMERIC PROANTHOCYANIDIN COMPLEXES ISOLATED FROM VARIOUS RAW PLANT MATERIALS

At present, the most widely and successfully used antioxidants are complexes of oligomeric proanthocyanidins (COPCs), which are considered as the most important biologically active additives [1]. These complexes are based on two monomer units, catechol and (–)-epicatechol, as well as on their galloyl derivatives. COPCs are obtained due to the ability of these compounds to form polymeric structures from two or more subunits [1]. Commercial raw material sources for the synthesis of COPCs are grape seeds (Vitis vinifera) and pine bark (Pinus maritima). COPCs obtained from pine bark are compositionally stable because the product originates from raw material of the same kind and proanthocyanidins are extracted by the same method [2]. In contrast, COPCs obtained from grape seeds can significantly differ in composition because different methods are employed for the extraction of biologically active substances and the raw material can represent various grape species. The high importance of COPCs for the human organism [1] and the wide use of these additives in food products are confirmed by the fact that a special committee was created in the USA for COPC quality control and the standardization of grape seed extracts on the market. However, no methods capable of adequately characterizing and evaluating these products have been developed so far. The purpose of this study was to develop a simple method for COPC standardization that would require no complicated equipment and could qualitatively characterize each COPC fraction, including phenolic acids (PAs), monomer catechols (MCs), low-molecular proanthocyanidins (LMPCs, n = 2 – 4), and high-molecular proanthocyanidins (HMPCs, n 5), as well as the distribution of antiradical activity (ARA) between these fractions. EXPERIMENTAL PART

GRAPES, GALLS, AND GEOGRAPHY: THE DISTRIBUTION OF NUCLEAR AND MITOCHONDRIAL DNA VARIATION ACROSS HOST-PLANT SPECIES AND REGIONS IN A SPECIALIST HERBIVORE

Studies of patterns of molecular variation in natural populations can provide important insights into a number of evolutionary problems. Among these, the question of whether geographic factors are more important than ecological factors in promoting population differentiation and ultimately speciation has been an important and contentious area in evolutionary biology. Systems involving herbivorous insects have played a leading role in this discussion. This study examined the distribution of molecular variation in a highly specialized gall-forming insect, grape phylloxera (Daktulosphaira vitifoliae Fitch), that is found on both sympatric and allopatric host-plant species of the genus Vitis. In addition, the relationship of insects in the introduced range in the United States to ancestral populations in the native range was examined. Evidence for differentiation along host-plant lines from both nuclear (RAPD) and mitochondrial (COI) DNA was confounded with the effect of geography. Differentiation was found where hosts were allopatric or parapatric, but no evidence was found for such differentiation on two hosts, V. vulpina and V. aestivalis, that are broadly sympatric. The question of population differentiation onto these sympatric hosts can be considered to be resolved--it has not occurred in spite of a long history of association. Evidence was equivocal, but suggestive of a period of divergence in allopatry prior to reestablishment of contact, for insects associated with another host plant species, V. cinerea, found in both sympatric and parapatric populations. A low level of diversity and placement of samples collected from the grape species V. riparia at the tip of a phylogenetic tree supports the hypothesis that this host has been recently colonized from populations from the Mississippi Valley. A polyphyletic origin for biotype B grape phylloxera was supported: Although most samples collected from vineyards in the introduced range in California had similar haplotypes, they were closely related to natives on V. vulpina from the Atlantic Coast-Piedmont region. All samples collected from vineyards in Oregon and Washington were closely related to natives on V. riparia in the northern United States.

In Situ Conservation of America's Wild Grapes

In Situ Conservation of America's Wild Grapes