Grafting Genotype Combination Effect of Vitis ssp. on Roots Phylloxeration Degree and Vigor of Grapevine

The present study investigated whether different grafting combinations (hypobiont-epibiont) of Vitis spp. influence root infection with phylloxera and thus vine biomass on potted 2-year-old plants. The study was conducted simultaneously at two locations in Slovenia (VEM) and Hungary (GF). The dormant canes of ‘Johanniter’ (JOH), ‘Riesling’ (RR) and Vitis berlandieri × Vitis riparia ‘Teleki 5C’ (5C) were hetero-grafted (each with each) and autografted (each with itself), so that nine plant combinations were used for the trial. The roots of the experimental plants at different ages (1–2 years) were infested with two phylloxera populations originating from two locations (VEM, GF). Plant growth was quantified 120 days after inoculation by measuring root and shoot biomass, while the extent of phylloxera infestation was assessed by the number of feeding sites (nodosities, tuberosities) and the number of larval stages of phylloxera. In most cases, the genotype of the hypobiont influenced the degree of phylloxera infestation on all roots of the two-year-old root system. At both locations, the highest number of nodosities and the highest increase in phylloxera population was observed on the autografted Teleki 5C (5C/5C). The phylloxera biotype derived from Vitis vinifera roots (GF) induced tuberosities, especially on roots of combinations where JOH and RR were used as hypobionts. No correlation was found between biomass and phylloxera infestation. The hypobiont genotype had no effect on cane biomass at the end of the growth cycle at either experimental site

DvEffector matches with effectors of <i>Acyrthosiphon pisum</i>.

DvEffector matches with effectors of Acyrthosiphon pisum.</p

Conserved DvEffectors with phytophagous insects.

A summary of the BlastP search results of the DvEffectors against salivary gland proteins of phytophagous insects with different feeding behaviour: Plant hoppers–vascular feeders (green): Nephotettix cincticeps [11], Nilaparvata lugens, Sogatella frucifera, Laodelphax striatellus [59]; Aphids—phloem feeders (blue): Acyrthosiphon pisum [15, 16], Myzus persicae, Rhopalosiphum padi, Myzus cerasi [24], Sitobion avenae [19]; Gall midges—gall feeders (rosa): Mayetiola destructor [61], Mayetiola avenae, Mayetiola hordei [60] and Stink bugs—non-phloem feeders (yellow): Halyomorpha halys and Nezara viridula [62]. Numbers within the circles indicated the ortholog matches (-value -50 and a bit score >100) between DvEffectors and the salivary gland proteins of at least one insect species within the insect feeding category.</p

Protein secretion pipeline applied to the <i>D</i>. <i>vitifoliae</i> salivary gland proteome.

Protein secretion pipeline applied to the D. vitifoliae salivary gland proteome.</p

Characterisation of the salivary gland proteome.

Gene ontology characterisation of the salivary gland proteome of D. vitifoliae larvae feeding on root galls of Teleki 5C (V. berlandieri x V. riparia). A) Protein top blast hit analysis ranked by species; B) Molecular weight distribution [kDa] of 1511 proteins of the salivary gland proteome and the secreted DvEffectors subset (420 proteins); C) GO enrichment analysis conducted with Blast2Go.</p

Analysed DvEffector genes and primers used for qRT-PCR.

Analysed DvEffector genes and primers used for qRT-PCR.</p

Relative gene expression levels of <i>D</i>. <i>vitifoliae</i> effector genes.

Expression levels [NRQ] of genes coding for A) conserved effectors of D. vitifoliae and A. pisum (Dv1-5) and B) false positives detected within the salivary gland proteome of D. vitifoliae but not associated to feeding (Fp1-3). RNA was extracted from salivary glands dissected from of feeding (SG0) and starving larvae (SG24). ActinA1 (DV3000100) was used as reference gene. Error bars indicate standard deviations of three independent biological replicates each consisting of salivary glands dissected from 100 individuals. Minor letters refer to significant differences obtained by Independent T-tests (p < 0.05).</p

Comparative Transcriptome Analysis of Two Root-Feeding Grape Phylloxera (D. vitifoliae) Lineages Feeding on a Rootstock and V. vinifera

Grape phylloxera is one of the most dangerous insect pests for worldwide viticulture. The leaf- and root-galling phylloxerid has been managed by grafting European grapevines onto American rootstock hybrids. Recent reports pinpoint the appearance of host-adapted biotypes, but information about the biomolecular characteristics underlying grape phylloxera biotypisation and its role in host performance is scarce. Using RNA-sequencing, we sequenced the transcriptome of two larval stages: L1 (probing) and L2-3 (feeding) larvae of two root-feeding grape phylloxera lineages feeding on the rootstock Teleki 5C (biotype C) and V. vinifera Riesling (biotype A). In total, 7501 differentially expressed genes (DEGs) were commonly modulated by the two biotypes. For the probing larvae, we found an increased number of DEGs functionally associated with insect chemoreception traits, such as odorant-binding proteins, chemosensory proteins, ionotropic, odorant, and gustatory receptors. The transcriptomic profile of feeding larvae was enriched with DEGs associated with the primary metabolism. Larvae feeding on the tolerant rootstock Teleki 5C exhibited higher numbers of plant defense suppression-associated DEGs than larvae feeding on the susceptible host. Based on the identified DEGs, we discuss their potential role for the compatible grape phylloxera–Vitis interaction belowground. This study was the first to compare the transcriptomes of two grape phylloxera lineages feeding on a tolerant and susceptible host, respectively, and to identify DEGs involved in the molecular interaction with these hosts. Our data provide a source for future studies on host adaptation mechanisms of grape phylloxera and help to elucidate grape phylloxera resistance further.</jats:p