Grape Roots Research Articles

Fungal infections of grapevine roots in phylloxera-infested vineyards

Wounds caused by feeding of grape phylloxera on grape roots can become infected with a variety of fungi. Fusarium roseum, F. oxysporum and Pythium ultimum are important in Vitis vinifera Chardonnay wounds whereas F. oxysporum and Cephalosporium sp. are important for the moderately tolerant rootstock AXR#1. Proportion of root lengths infected in the phloem parenchyma were measured in two vineyards through the 1996 growing season and into the winter. Infection rates were highest in spring (as measured in May) but decreased to a low level by the end of summer. There was a second infection peak in fall. We suggest that the decline in fungal infections was due to death of highly infected roots and their removal from the sampled pool of roots. Loss of roots is a logical cause of vine decline and explains why there have been poor correlations between phylloxera populations and vine damage symptoms.

Effects of intercropping vines with tobacco and root extracts of tobacco on grape phylloxera, Daktulosphaira vitifoliae Fitch

The effects of grape-tobacco intercropping patterns on populations of grape phylloxera, Daktulosphaira vitifoliae Fitch, as well as on the growth and development of the infested vines were evaluated in the field and the impact of an aqueous tobacco root extract on grape phylloxera was evaluated using a laboratory bioassay. The aqueous tobacco root extract exhibited biological activity against this pest. The egg mortality, nymph mortality, development period, life span and female fecundity were significantly affected. In the field trial, grape phylloxera populations were clearly lower as compared to the monoculture pattern. However, the rates of newly developed roots and newly infested grape roots were significantly higher and lower, in intercropping patterns than in the vine monoculture, respectively. The grape phylloxera population number on the grape roots decreased each year, and the vine trees gradually renewed upon continuous intercropping with tobacco over three years. These results confirmed that intercropping grapes with tobacco can effectively control grape phylloxera in an infested vineyard. The results also indicated that additional crops could be intercropped with grapes and are effective against grape phylloxera, which should be explored as an integrated approach for controlling the pest.

Changes of mycorrhizal colonization along moist gradient in a vineyard of Eger (Hungary)

Abstract The role of mycorrhizal fungi has special importance in the case of low soil moisture because the colonization of vine roots by mycorrhiza increases water and nutrient uptake and thus aids the avoidance of biotic and abiotic stresses of grape. Our aim was to investigate in the Eger wine region the changes of mycorrhizal colonization, water potential, and yield quality and quantity of grape roots at three altitudes, along a changing soil moist gradient. Our results show that the degree of mycorrhizal colonization is higher in drier areas, which supports the water and nutrient uptake of the host plant.

CLONING AND CHARACTERIZATION OF THE DAGGER NEMATODE RESISTANCE GENE XIR1

The dagger nematode, Xiphinema index, feeds aggressively on grape roots and in the process vectors grapevine fanleaf virus (GFLV) leading to the severe viral disease known as fanleaf degeneration. Disease symptoms consist of disrupted fruit set caused by GFLV and depressed plant growth caused by root damage from X. index. The use of fumigants to control X. index in vineyards is no longer recommended because of their high cost, detrimental environmental effects and lack of effective soil penetration to control nematodes on a deep perennial root system. Therefore, resistance to X. index has been an important objective in grape rootstock breeding programs. We previously demonstrated that resistance to X. index derived from a Vitis arizonica/girdiana hybrid b42-26 was largely controlled by a major quantitative trait locus, XiR1 (X. index Resistance 1) located on chromosome 19. Genetic studies leading to the isolation and characterization of the genes conferring resistance to X. index would further our understanding of resistance and assist molecular and classical breeding efforts to control X. index. In this report, we present the development of high resolution genetic and physical maps in the XiR1 region as well as the isolation of the XiR1 locus by a positional cloning approach. This study has identified the first locus responsible for ectoparasitic nematode resistance. The markers developed from this study are being used to expedite the breeding of resistant grape rootstocks.

Spatial Distribution of Grape Root Borer (Lepidoptera: Sesiidae) Infestations in Virginia Vineyards and Implications for Sampling

Grape root borer, Vitacea polistiformis (Harris) (Lepidoptera: Sesiidae) is a potentially destructive pest of grape vines, Vitis spp. in the eastern United States. After feeding on grape roots for ≍2 yr in Virginia, larvae pupate beneath the soil surface around the vine base. Adults emerge during July and August, leaving empty pupal exuviae on or protruding from the soil. Weekly collections of pupal exuviae from an ≍1-m-diameter weed-free zone around the base of a grid of sample vines in Virginia vineyards were conducted in July and August, 2008-2012, and their distribution was characterized using both nonspatial (dispersion) and spatial techniques. Taylor's power law showed a significant aggregation of pupal exuviae, based on data from 19 vineyard blocks. Combined use of geostatistical and Spatial Analysis by Distance IndicEs methods indicated evidence of an aggregated pupal exuviae distribution pattern in seven of the nine blocks used for those analyses. Grape root borer pupal exuviae exhibited spatial dependency within a mean distance of 8.8 m, based on the range values of best-fitted variograms. Interpolated and clustering index-based infestation distribution maps were developed to show the spatial pattern of the insect within the vineyard blocks. The temporal distribution of pupal exuviae showed that the majority of moths emerged during the 3-wk period spanning the third week of July and the first week of August. The spatial distribution of grape root borer pupal exuviae was used in combination with temporal moth emergence patterns to develop a quantitative and efficient sampling scheme to assess infestations.

Gene expression profiling of rootstock ‘140Ru’ and Vitis vinifera L. cv. ‘Crimson Seedless’ grape roots infected with grape phylloxera

Grape phylloxera (Daktulosphaira vitifolia Fitch) is the most devastating pest of grape. Information concerning the molecular basis of grape root–phylloxera interactions will enhance the future development of effective management tools against this pest. In this study, changes in gene transcript abundance in grape roots in response to phylloxera infestation were measured using the Affymetrix Vitis vinifera Genome Array. Two genetically related grape roots, rootstock ‘140Ru’ (potted ‘140Ru’, which forms nodosities but no tuberosities in response to phylloxera infestation) and V. vinifera L. cv. ‘Crimson Seedless’ (which forms both nodosities and tuberosities) were utilized in the current study. Pairwise comparisons followed by false discovery rate analysis indicated that the expression levels of 1,204 transcripts changed significantly in ‘140Ru’; 599 increased and 625 decreased. However, in ‘Crimson Seedless’, the expression of 799 transcripts changed significantly, including 305 that increased and 494 that decreased. Comparative analysis of these transcripts indicated that a total of 155 transcripts were common to both resistance and susceptible responses. In this set, the levels of 48 transcripts increased in ‘140Ru’ but decreased in ‘Crimson Seedless’. Quantitative real-time RT-PCR confirmed the results of the microarray analysis. Since nodosities potentially function as nutrient reservoirs, probe sets corresponding to the categories of energy metabolism and carbohydrate metabolism were more commonly induced in ‘Crimson Seedless’. Defense responses of ‘140Ru’ to phylloxera attack were detected. Probe sets that were uniquely induced in ‘140Ru’ are associated with the biosynthesis of secondary metabolites. This study may aid in the identification of genes involved in plant defenses against grape phylloxera.

Behavioral Response of Grape Root Borer (Lepidoptera: Sesiidae) Neonates to Grape Root Volatiles

Grape root borer, Vitacea polistiformis (Harris), is an oligophagous and potentially destructive pest of grape in commercial vineyards throughout much of the eastern United States. Larvae feed on vine roots, although little is known about their below-ground interactions with host plants. The behavioral response of groups of grape root borer neonates to stimuli from host and nonhost roots was evaluated in single and paired stimuli bioassays in which stimuli were presented in opposing wells attached to the bottom of petri dish arenas. Stimulus sources included root pieces and root headspace volatiles from 3309 and 420-A grape rootstocks (host) and apple (nonhost) and ethanol-based extracts of 3309 and 420-A roots. In single stimulus assays, significantly more larvae were recovered from wells containing grape roots, apple roots, grape extracts, and grape root volatiles than from control wells, but there was no significant response to volatiles collected from the headspace of apple roots. In paired stimuli assays, significantly more larvae were recovered from wells containing grape than apple roots. There was no difference in larval distribution between wells when 420-A and 3309 roots were presented simultaneously, although a significantly greater response to 3309 than 420-A root extract was recorded. When soil was added to the assays, significantly more larvae were recovered from wells containing grape roots than from those containing only soil, but this response was not detected in assays using buried apple roots. These results are discussed in relation to the plant-insect interactions between grape root borer larvae and their Vitaceae hosts.

Comparison of root anatomy and xylem vessel structure in rain-fed and supplementary irrigated ‘Yaghooti-Syah Shiraz’ grapevine (Vitis vinifera L.)

Changes in environmental conditions may lead to modifications in structural development of plant root. Effects of supplementary irrigation and soil depths (0–90 cm) on anatomical changes in xylem were investigated in rain-fed Vitis vinifera L. cv. Yaghooti-Syah Shiraz. Irrigated and control roots were prepared according to routine histological procedure. Light microscopic observations revealed the structural features of drought tolerant control roots and their changes after the treatment. Irrigated roots were characterized by the absence of starch grains in parenchyma cells, uniformity of parenchymatous pith cells, and a decrease in periderm thickness. Morphometric investigation of xylem showed that irrigated and deep roots had larger mean and maximum vessel diameter and fewer vessel number than rain-fed and shallow roots, at every soil depth of every treatment. Secondary xylem vessel diameter and number were more affected by irrigation and soil depths than metaxylem. Grape roots responded to supplementary irrigation and increasing soil depth by reducing protective and supporting tissues and increasing vessel diameter.

Delayed response to ring nematode (Mesocriconema xenoplax) feeding on grape roots linked to vine carbohydrate reserves and nematode feeding pressure

The chronic impact of ring nematode (Mesocriconema xenoplax) feeding on grapevine (Vitis vinifera) was studied under controlled conditions. ‘Pinot noir’ grapevines were exposed to ring nematode or kept nematode-free for three growing seasons and vines were either grown in full sunlight, 15% of full sun, or partially defoliated to manipulate vine carbohydrate status. Whole plants were destructively sampled to assess the impact of ring nematode on whole plant biomass, carbohydrate, and mineral nutrient accumulation. Vine shoot growth and total biomass was unaffected by ring nematode in the first growing season, although reserves of nonstructural carbohydrates (NSC), P, K, and Ca in the roots and wood were reduced in all canopy management treatments. Vine shoot growth and total biomass were reduced by ring nematode in Year 2, and greater declines in reserve NSC and most mineral nutrients had occurred. Reserves of NSC were affected more than biomass or nutrients during the second year. During the third year of exposure to ring nematode, vines in the 15% sun treatment were dying (prompting an earlier destructive harvest), even though these vines had similar biomass and NSC reserves as the partially defoliated vines at the end of the second year. The demise of the 15% sun vines was associated with higher ring nematodes per unit of root mass, as compared to either full sun or defoliated vines. Therefore, predicting plant response to this nematode requires an understanding of nematode density per quantity of roots, not nematodes per unit of soil which is how plant parasitic nematodes are currently enumerated.

NEW TREND FOR Meloidogyne javanica MANAGEMENT BY Myrothecium verrucaria (DITERA) AS PROMISING BIOLOGICAL AGENT.

Evaluation of DiTera a commercial formulation of Myrothecium verrucaria against Meloidogyne javanica was examined in-vitro for mortality, greenhouse as well as field trials on tomato and grape using various rates and method of applications. In-vitro test revealed a positive correlation between M. javanica J­2 mortality and biocide compound rate and concentration at various exposure periods. Larval mortality significantly increased with the increase of rates and concentrations from 10 up to 30%, as well, whereas, a slightly increase in M. javanica J­2 mortalitywas insignificantly noticed according to the tested two temperatures. With respect to tomato greenhouse trial, all tested DiTera rates and type of applications obviously caused remarkable increase in tomato growth cv. Castle Rock. Among DiTera rates, treatment at 0.3 g / seedling ranked first in increasing percentage of fresh weight of the whole plant with values of 56.73, 41.70 and 77.32% for the three type of applications i.e. at planting, post planting and pre planting respectively. As the rates of DiTera increased from 0.1 up to 0.3 g/ seedling, the percentage increase values of such plant growth parameter increased from 21.26 to 41.70%; 36.6 to 56.73%; and 57.5 to 77.32% for post planting, at planting and pre- planting application, respectively. Similar trend was noticed for suppressing nematode parameters, where the pre-planting application ranked first with values of 85.2, 89.2 and 94.1%, for the rate of 0.1, 0.2 and 0.3 g/ seedling, respectively. Moreover, It is worthy to note that there was a positive correlation between the rate of nematode build-up and DiTera compound rates, whereas this nematode criterion recorded to be the least value (0.26) by oxamyl treatment. Meanwhile, in tomato field trial, the rate of 0.3 g/ tomato seedling significantly decreased the number of galls on tomato roots with reduction percentages of 85.8, 71.0 and 59.7% for the pre-, at- and post- planting applications, respectively. All tested DiTera rates along with application times reduced tested nematode parameters. Among the three application times, the pre-planting method of adding DiTera compound accomplished the highest reduction percentages of nematode population densities with values of 74.3, 82.2 and 85.2 for 0.1, 0.2 and 0.3 g /plant respectively. Regarding grape greenhouse and field trials, all tested DiTera applications i.e. 2 g/plant 4 , 5, and 6 times at one week interval in both greenhouse and field trials obviously showed protection performance in grape plants cv. Thompson against nematode infestation of M. javanica in terms of reduction percentages of tested nematode parameters on grape roots as well. Likewise, as the addition of 2 g/ plant raised from four up to six times at one week interval, nematode criteria significantly decreased. Plants receiving DiTera treatments six times accomplished the highest reduction percentages in nematode parameters followed by that of five times and then four times applications. Moreover, oxamyl treatment twice at one month interval surpassed all tested DiTera application in suppressing nematode population, number of galls and eggmasses in both trials.

Cloning and characterization of XiR1, a locus responsible for dagger nematode resistance in grape

The dagger nematode, Xiphinema index, feeds aggressively on grape roots and in the process, vectors grapevine fanleaf virus (GFLV) leading to the severe viral disease known as fanleaf degeneration. Resistance to X. index and GFLV has been the key objective of grape rootstock breeding programs. A previous study found that resistance to X. index derived from Vitis arizonica was largely controlled by a major quantitative trait locus, XiR1 (X. index Resistance 1), located on chromosome 19. The study presented here develops high-resolution genetic and physical maps in an effort to identify the XiR1 gene(s). The mapping was carried out with 1,375 genotypes in three populations derived from D8909-15, a resistant selection from a cross of V. rupestris A. de Serres (susceptible) × V. arizonica b42-26 (resistant). Resistance to X. index was evaluated on 99 informative recombinants that were identified by screening the three populations with two markers flanking the XiR1 locus. The high-resolution genetic map of XiR1 was primarily constructed with seven DNA markers developed in this study. Physical mapping of XiR1 was accomplished by screening three bacterial artificial chromosome (BAC) libraries constructed from D8909-15, V. vinifera Cabernet Sauvignon and V. arizonica b42-26. A total of 32 BAC clones were identified and the XiR1 locus was delineated within a 115 kb region. Sequence analysis of three BAC clones identified putative nucleotide binding/leucine-rich repeat (NB-LRR) genes. This is the first report of a closely linked major gene locus responsible for ectoparasitic nematode resistance. The markers developed from this study are being used to expedite the breeding of resistant grape rootstocks.

Biological and environmental factors controlling root dynamics and function: effects of root ageing and soil moisture

Understanding factors controlling root dynamics and functioning can lead to more efficient and profitable vineyard management. However, our current understanding of root dynamics and their regulation by plant and environmental factors is limited, particularly under field conditions. This paper presents current understanding of grape root dynamics, highlighting studies using minirhizotron cameras, which directly assess root dynamics, and experiments on roots of known age, which link root phenology and function. Data summarised here show timing of grape root production varies widely among different regions, as well as among rootstocks and canopy management systems in the same region. Timing of production can be responsive to differences in soil moisture. Lifespan of grape roots, however, appears less affected by soil moisture because of nocturnal hydraulic redistribution. Root function, such as capacity for P and N uptake, declines rapidly with root age. Differences in timing and spatial distribution of root production can effect above-ground growth and vineyard water-use efficiency. Improving our understanding of when roots grow and are functionally active in agricultural systems can lead to improved water and fertiliser applications, and more precise vineyard management. Because both environmental and biological factors affect root dynamics, simple predictions of timing of root production or standing populations with shoot development are unlikely to be achieved. However, with multi-year data on root dynamics, and environmental and biological factors, regionally specific models of root populations and their functioning may be possible to develop.

The diversity of arbuscular mycorrhizal fungi amplified from grapevine roots (Vitis vinifera L.) in Oregon vineyards is seasonally stable and influenced by soil and vine age

The diversity of arbuscular mycorrhizal fungi (AMF) in 10 Oregon vineyards was assessed by examining spores in soil and amplifying mycorrhizal DNA from roots. Seventeen spore morphotypes were found in soil, including seven species in the Acaulosporaceae. Eighteen phylotypes were amplified from grape roots with AM1 and NS31 primers, and clones were dominated by Glomus spp. (> 99%). A few clones (< 1%) representing a single phylotype within Gigasporaceae, and a single clone within Archaeosporaceae were amplified from roots with AM1-NS31 primers. A separate experiment employing known proportions of grape roots colonized by Glomus intraradices or by Gigaspora rosea showed that fungi within Gigasporaceae might be underrepresented in clone abundance when Glomus spp. co-occur in roots. No clones representing fungi within the Acaulosporaceae were amplified from vineyards, although specific fungi within Acaulosporaceae were shown to colonize Pinot noir roots in sterilized soil and were amplified from these roots. Four Glomus phylotypes, including G. intraradices, were found in roots from all 10 vineyards, and these fungi accounted for 81% of clones. AMF phylotypes amplified from roots did not change during the growing season, although six phylotypes varied with soil type. The presence of three phylotypes was affected by vineyard age, and phylotype richness appeared to decline as vineyard age increased beyond 20 y. PCA analysis supported the hypothesis that the AMF community is different in red-hill soils than in valley soils and indicated certain phylotypes might be associated with lower soil and vine nutrient status. However, the changes in the AMF community in grape roots across vineyards were subtle because most root samples were dominated by the same three or four phylotypes. A separate analysis using primers to amplify AMF from the Archeasporaceae/Paraglomeraceae showed most root samples also were colonized by at least one Paraglomus or Archaeospora phylotype.

Ring nematodes ( Mesocriconema xenoplax) alter root colonization and function of arbuscular mycorrhizal fungi in grape roots in a low P soil

A reduction of arbuscules in roots of grapevines ( Vitis vinifera) observed when ring nematodes were added to field microplots led to the hypothesis that nematode feeding suppresses arbuscules by competing for root carbohydrates. Support for this hypothesis was tested by growing ‘Pinot noir’ grapevines in a factorial experiment with three levels of initial nematode densities (0, 0.1, 1.0 nematodes g −1 soil), two levels of light (full sun, 50% sun), and two levels of AMF (nonAMF, +AMF). Effects on plant growth were primarily driven by a light and AMF treatment interaction, such that low light increased stem dry matter accumulation at the expense of roots in +AMF vines only. Nematodes had only a minor influence on plant growth (leaf mass was reduced at the highest nematode density), but nematodes did not affect overall plant dry matter accumulation. Since nonAMF vines were severely limited by P and their growth was so poor, the impact of nematode and light treatments was further analyzed in +AMF plants only. Nematode populations, AMF colonization, and root carbohydrates were differentially affected by initial nematode density or light levels. Root biomass, and reducing sugar and starch concentrations in fine roots were reduced by low light, but the final nematode populations and arbuscule frequencies in roots were unaffected by light. Nematodes reduced arbuscules and starch concentrations in fine roots, but did not affect total colonization by AMF (hyphae, vesicles or arbuscules). Nematodes reduced plant P and K uptake at the highest density, and low light reduced Mg uptake. These findings are consistent with the hypothesis that ring nematodes suppress arbuscules in roots via competition for root carbohydrates. However, the lack of a treatment interaction between light and nematodes in our study suggests that ring nematode–AMF interactions in grape roots are controlled by more than competition for photosynthate.

MODELING CARBON ALLOCATION BELOW GROUND

Belowground carbon expenditure has been difficult to measure, and even more so to predict. Root growth is influenced by both direct effects on plant metabolism and indirect effects of soil drying and interactions with soil organisms. In Concord grape, crop load may compete with root growth when soil moisture is not limiting. Root lifespan also is difficult to predict but some success can be achieved by taking a cost-benefit perspective to unraveling some of the processes affecting root lifespan. Root respiration is affected by both short- and long-term temperature conditions. Short-term studies suggested that elevated soil temperature may have direct effects on root respiration that follow a Q10 response of about 1.7 2. More recent work indicates that plant respiratory responses to soil temperature may be a function of plant growing temperature and soil moisture. Citrus and grape roots exposed to increasing temperatures above 20 °C for more than three days exhibited homeostatic respiratory responses, presumably to avoid excess carbohydrate metabolism. Moreover, citrus roots in dry soil exhibited no temperature response but maintain respiration at a stable basal rate.

Chromosome and plasmid-encoded N-acyl homoserine lactones produced by Agrobacterium vitis wildtype and mutants that differ in their interactions with grape and tobacco

Agrobacterium vitis causes crown gall disease on grapevines. It also induces a specific necrosis on grape roots and a hypersensitive response (HR) on tobacco that are regulated by a complex quorum-sensing regulatory system. Strain F2/5 produces at least six N-acyl-homoserine lactones (AHLs) that function as signal molecules in quorum-sensing. The AHLs differ in acyl side chain length (8–16 carbons) as determined by gas chromatography/mass spectrometry and electrospray ionization tandem mass spectrometry. Mutant derivatives of F2/5 differ in ability to cause necrosis and the HR and show variable AHL profiles as determined by a thin-layer chromatography/biosensor assay. All wildtype A. vitis strains revealed the presence of long-chain AHLs regardless of tumorigenicity or ability to cause the HR. Whereas genes encoding long-chain AHLs are predicted to reside on the F2/5 chromosome, the determinants for short-chain AHLs were shown to be located on conjugal plasmids.

Interactions of three species of plant-parasitic nematodes with arbuscular mycorrhizal fungus, Glomus macrocarpus, and their effect on grape biochemistry

AbstractThe arbuscular mycorrhizal fungus (AM fungus),Glomus macrocarpus, and the nematodes, Meloidogyne incognita and Tylenchulus semipenetrans, have negative reciprocal effects on spore production, nematode development and reproduction when coinfecting grape roots. Glomus macrocarpus was antagonistic to Rotylenchulus reniformis development and reproduction whilst the nematode was synergistic to spore production. Glomus macrocarpus alone or in combination with M. incognita or T. semipenetrans increased root protein, total soluble sugars, total carbohydrates and decreased lipids and dry matter. Glomus macrocarpus together with R. reniformis decreased protein, total soluble sugars, total carbohydrates and dry matter and greatly increased lipids. Compared to the healthy control, G. macrocarpus alone or in combination with M. incognita or R. reniformis decreased the N, P and K content of leaves. Glomus macrocarpus together with T. semipenetrans improved N, P and K concentrations but the latter was still less than that of healthy plants.

An assessment method for the quantification of Daktulosphaira vitifoliae (Fitch) (Hem., Phylloxeridae) populations in the field

Abstract: Grape phylloxera is a plant parasite that has started to become a pest again in European viticulture in spite of the use of grafted rootstocks. Since the middle of the 1980s, there have been various reports of vine damage caused by phylloxera. It was shown that in some cases there is no direct correlation between the occurrence of phylloxera and vine damage. In this context, phytopathogenic microorganisms, especially fungi, are mentioned in literature. To investigate the possible interactions it is necessary to be able to assess phylloxera populations in the field, e.g. to correlate phylloxera abundance with the vigour of the vines. Because of the non‐homogenous distribution of the grape roots in the soil and of phylloxera on the roots, a method that meets these conditions was established. For the root sampling, a method that ensures reproducible numbers and a high probability of root detection was developed. The second component of the method is a ranking system for the visual assessment of the populations. For the validation of the assessment system, the absolute number of phylloxera feeding sites, all phylloxera instars and phylloxera eggs were related to the weight of fresh and dry roots. The statistical analysis has shown a significant differentiation between the assessment classes (P ≤ 0.01). Furthermore, a correlation (R2 = 0.732) between the phylloxera populations, assessed with this method, and soil temperatures could be shown. Such a correlation was shown in various studies and, therefore, supports the validity of the assessment system presented in this paper.

Development and transferability of apricot and grape EST microsatellite markers across taxa.

EST microsatellite markers were developed in apricot (Prunus armeniaca L.) and grape (Vitis vinifera L.). cDNA libraries from either apricot leaves or grape roots were used in an enrichment procedure for GA and CA repeats. The transferability of EST simple sequence repeat (SSR) markers from apricot and grapevine to other related and unrelated species was examined. Overall, grape primers amplified products in most of the Vitaceae accessions while the apricot primers amplified polymorphic alleles only in closely related species of the Rosaceae. In this taxonomic family, ten EST SSR loci were tested, and one single primer pair, PacB22, was amplified across species and sections in the Prunoideae and Maloideae. Sequencing of EST SSR loci in other species and genera confirmed a higher level of conservation in the microsatellite motif and flanking regions in the Vitaceae compared to the Rosaceae. Two distinct fragments of the PacB22 locus amplified across the Malus and Pyrus genera; however, while the coding region was highly conserved, the microsatellite repeat motif was no longer present. The banding pattern was explained by base substitution and insertion/deletion events in the intronic region of PacB22. This study includes the determination of the degree of polymorphism detected among species and genera in two unrelated taxonomic families and the evaluation of the information provided by the microsatellite repeats and the flanking regions.

Histological Investigations on Infection of Grape Roots and Shoots by «Phaeoacremonium» spp.

Tissue-cultured grapevines cv. Cabernet Sauvignon were used to determine whether injury is a prerequisite to penetration of shoot and root tissue by Phaeoacremonium spp. and to ascertain the path of invasion inside the host. Uninjured and injured roots and shoots were inoculated with P. inflatipes and P. aleophilum at approximately 106 spores ml-1. Isolation and scanning electron microscopy observations showed that Phaeoacremonium spp. was capable of penetrating uninjured roots and shoots. Light microscopy observations of paraffin embedded sections showed that rapid spread of the fungus in roots was through the vascular tissues and intercellular spaces of the cortex. In the shoots, spread of the fungus was initially through the intercellular spaces of the epidermis, cortex, and pith; rapid spread apparently occurred in the intercellular spaces of the pith. Spores were seen in the pith area as well as in the xylem. Remote from the point of inoculation, hyphae were seen in the epidermis, cortex, pith, and vascular tissues without noticeable change in appearance of the invaded cells. Symptoms of the disease were observed in some plants 2 months after inoculation but isolations made in symptomless plants after 2 weeks showed the presence of the fungus in all parts of the plant.