Vector Of Grapevine Fanleaf Virus Research Articles

NEMATOFAUNA PRESENT IN THE VENETIAN VINEYARD

Attacks of plant-parasitic nematodes can seriously affect grapevine yield and quality, also due to synergistic damages caused by the co-presence of nematodes and viruses. A survey was carried out in vineyards from a D.O.C.G. area of Veneto region, Italy, in order to better understand the relationship between grapevine plants and presence of phytonematodes. Most concerns were raised by detection of species as Mesocriconema xenoplax and Xiphinema index, this latter as the vector of grapevine fanleaf virus (GFLV), the most economically important nepovirus in vineyards. Some individuals of Pratylenchus vulnus were also found. Numerous predaceous nematodes as Mononchida were found within several soil samples. Mononchida play an important role in contrasting the spread of other nematodes, including plant-parasitic nematodes. During the survey, other non-plant-parasitic nematodes as Dorylaimina and Rhabditida were homogeneusly distribuited among samples. Key Words: grapevine, Grapevine fanleaf virus (GFLV), nematodes, trophic groups, Xiphinema index.

Characterization of the Biogenic Volatile Organic Compounds (BVOCs) and Analysis of the PR1 Molecular Marker in Vitis vinifera L. Inoculated with the Nematode Xiphinema index.

Upon pathogen attack, plants very quickly undergo rather complex physico-chemical changes, such as the production of new chemicals or alterations in membrane and cell wall properties, to reduce disease damages. An underestimated threat is represented by root parasitic nematodes. In Vitis vinifera L., the nematode Xiphinema index is the unique vector of Grapevine fanleaf virus, responsible for fanleaf degeneration, one of the most widespread and economically damaging diseases worldwide. The aim of this study was to investigate changes in the emission of biogenic volatile organic compounds (BVOCs) in grapevines attacked by X. index. BVOCs play a role in plant defensive mechanisms and are synthetized in response to biotic damages. In our study, the BVOC profile was altered by the nematode feeding process. We found a decrease in β-ocimene and limonene monoterpene emissions, as well as an increase in α-farnesene and α-bergamotene sesquiterpene emissions in nematode-treated plants. Moreover, we evaluated the PR1 gene expression. The transcript level of PR1 gene was higher in the nematode-wounded roots, while in the leaf tissues it showed a lower expression compared to control grapevines.

THE GENETIC MAPPING OF XIPHINEMA INDEX RESISTANCE DERIVED FROM VITIS ARIZONICA

A breeding program to develop rootstocks with resistance to Xiphinema index, the dagger nematode vector of grapevine fanleaf virus (GFLV), has been underway for many years at UC Davis. A mapping population (0705) derived from 161-49C × R8916-22 was created in 2007 to develop an SSR-based linkage map for X. index resistance. 161-49C is a commercial rootstock susceptible to X. index feeding and R8916-22 is a heterozygous resistant cross originating from b40-14, a form of Vitis arizonica. Preliminary results suggest a 1:1 resistant:susceptible segregation ratio for X. index under greenhouse conditions. Previous studies showed that X. index resistance was controlled by a single homozygous locus. To date, 190 of 400 SSR markers were polymorphic, with coverage on all 19 linkage groups. These markers and others are being applied to the entire 0705 population to complete a genetic map of this excellent source of X. index resistance.

Local and systemic mycorrhiza-induced protection against the ectoparasitic nematode Xiphinema index involves priming of defence gene responses in grapevine

The ectoparasitic dagger nematode (Xiphinema index), vector of Grapevine fanleaf virus (GFLV), provokes gall formation and can cause severe damage to the root system of grapevines. Mycorrhiza formation by Glomus (syn. Rhizophagus) intraradices BEG141 reduced both gall formation on roots of the grapevine rootstock SO4 (Vitis berlandieri×V. riparia) and nematode number in the surrounding soil. Suppressive effects increased with time and were greater when the nematode was post-inoculated rather than co-inoculated with the arbuscular mycorrhizal (AM) fungus. Using a split-root system, decreased X. index development was shown in mycorrhizal and non-mycorrhizal parts of mycorrhizal root systems, indicating that both local and systemic induced bioprotection mechanisms were active against the ectoparasitic nematode. Expression analyses of ESTs (expressed sequence tags) generated in an SSH (subtractive suppressive hybridization) library, representing plant genes up-regulated during mycorrhiza-induced control of X. index, and of described grapevine defence genes showed activation of chitinase 1b, pathogenesis-related 10, glutathione S-transferase, stilbene synthase 1, 5-enolpyruvyl shikimate-3-phosphate synthase, and a heat shock proein 70-interacting protein in association with the observed local and/or systemic induced bioprotection against the nematode. Overall, the data suggest priming of grapevine defence responses by the AM fungus and transmission of a plant-mediated signal to non-mycorrhizal tissues. Grapevine gene responses during AM-induced local and systemic bioprotection against X. index point to biological processes that are related either to direct effects on the nematode or to protection against nematode-imposed stress to maintain root tissue integrity.

Development of nine polymorphic microsatellite markers for the phytoparasitic nematode Xiphinema index, the vector of the grapevine fanleaf virus

We report isolation, characterization and cross-species amplification of nine microsatellite loci from the phytoparasitic nematode Xiphinema index, the vector of grapevine fanleaf virus. Levels of polymorphism were evaluated in 62 individuals from two X. index populations. The number of alleles varies between two and 10 depending on locus and population. Observed heterozygosity on loci across both populations varied from 0.32 to 0.857 (mean 0.545). The primers were tested for cross-species amplification in three other species of phytoparasitic nematodes of the Xiphinema genus. These nine microsatellite loci constitute valuable markers for population genetics and phylogeographical studies of X. index.

OCCURRENCE OF XIPHINEMA INDEX IN LEBANESE VINEYARDS

SUMMARY Soil samples were collected in late spring 2005 from vineyards in 25 different locations of the Bekaa valley, the main grapevine-growing area of Lebanon, to investigate the presence of the longidorid nematode Xiphinema index Thorne & Allen, the vector of Grapevine fanleaf virus (GFLV). Approximately 14% of the samples contained the nematode, which was found in all developmental stages except for males, which are very rare in this species. The density of the nematode population ranged from 8 to 45 specimens/500 ml of soil. The main morphological characteristics of taxonomic relevance in the Lebanese population of X. index are described, while selected morphometric parameters from a population of 18 specimens were compared with those reported in the literature. This is the first survey for the presence and distribution of X. index in Lebanon.

Research Note virus transmission by grape phylloxera (Daktulosphaira vittfoliae Fitch)

Grape phylloxera (Daktulosphaira vitifoliae FITCH) infests immature roots of both Vitis vinifera L. and phylloxera resistant rootstocks. A capability to transmit viticultural viruses would make grape phylloxera a phytosanitary threat even under conditions where direct damage by the insect is not likely. We tested the hypothesis that phylloxera could transmit grapevine fanleaf virus (GFLV) by planting infected and non-infected vines in common 10 liter pots and infecting roots of the infected vine with grape phylloxera. In this test infection of a previously non-infected plant in the absence of nematode population suggests that grape phylloxera is a vector of GFLV.

Isolation and characterisation of microsatellites for Xiphinema index using degenerate oligonucleotide primed PCR

Abstract A short insert genomic library for Xiphinema index, the natural vector of Grapevine Fanleaf Virus, was constructed from degenerate oligonucleotide primed PCR (DOP-PCR) products. The genomic library was screened for (CA)n microsatellites. Screening of 6200 colonies and comparison of the sequencing results revealed seven (CA)n containing microsatellites, coded here as XIMSL1, XIMSL2, XIMSL3, XIMSL4, XIMSL5, XIMSL6 and XIMSS1. XIMSL prefixed microsatellites were followed by the motif of the same long interspersed element. Microsatellite XIMSS1 has some similarity to the short interspersed element. Except for XIMSL1, all microsatellites were proven to be effective diagnostic tools at species level. Genetic diversity between and within populations was also evaluated for each microsatellite.

Distribution of parasitic nematodes in vineyards in central and north-eastern Victoria

A survey of 16 1 vineyards in central and north-eastern Victoria determined the distribution of plant parasitic nematodes, particularly Xiphinema index, a vector of grapevine fanleaf virus. From the North-Central and Geelong Vine Disease Districts respectively, 185 and 3 soil samples were collected between 1978 and 1982. Fifteen genera of stylet-bearing nematodes were found, and those of known or suspected economic importance were Helicotylenchus (found in 24% of samples), Pratylenchus (21%), Xiphinema ( 13%), Criconemella (8%), Longidorus (7%) and Paratrichodorus (2%) . X. index was found in three samples from two vineyards, both within 10 km of Rutherglen in north-eastern Victoria. Neither Meloidogyne javanica nor Tylenchulus semipenetrans were detected, although both are common in other viticultural areas of Victoria.