Luca Zulini

Identification of Biomarkers for Defense Response to Plasmopara viticola in a Resistant Grape Variety

Downy mildew (Plasmopara viticola) is one of the most destructive diseases of the cultivated species Vitis vinifera. The use of resistant varieties, originally derived from backcrosses of North American Vitis spp., is a promising solution to reduce disease damage in the vineyards. To shed light on the type and the timing of pathogen-triggered resistance, this work aimed at discovering biomarkers for the defense response in the resistant variety Bianca, using leaf discs after inoculation with a suspension of P. viticola. We investigated primary and secondary metabolism at 12, 24, 48, and 96 h post-inoculation (hpi). We used methods of identification and quantification for lipids (LC-MS/MS), phenols (LC-MS/MS), primary compounds (GC-MS), and semi-quantification for volatile compounds (GC-MS). We were able to identify and quantify or semi-quantify 176 metabolites, among which 53 were modulated in response to pathogen infection. The earliest changes occurred in primary metabolism at 24–48 hpi and involved lipid compounds, specifically unsaturated fatty acid and ceramide; amino acids, in particular proline; and some acids and sugars. At 48 hpi, we also found changes in volatile compounds and accumulation of benzaldehyde, a promoter of salicylic acid-mediated defense. Secondary metabolism was strongly induced only at later stages. The classes of compounds that increased at 96 hpi included phenylpropanoids, flavonols, stilbenes, and stilbenoids. Among stilbenoids we found an accumulation of ampelopsin H + vaticanol C, pallidol, ampelopsin D + quadrangularin A, Z-miyabenol C, and α-viniferin in inoculated samples. Some of these compounds are known as phytoalexins, while others are novel biomarkers for the defense response in Bianca. This work highlighted some important aspects of the host response to P. viticola in a commercial variety under controlled conditions, providing biomarkers for a better understanding of the mechanism of plant defense and a potential application in field studies of resistant varieties.

Downy mildew resistance evaluation in 28 grapevine hybrids promising for breeding programs in Trentino region (Italy)

Downy mildew is a major grapevine disease caused by the biotrophic oomycete, Plasmopara viticola. Numerous disease resistance studies of diverse Vitis germplasm have been previously carried out to identify downy mildew resistance sources; however, ratings were mainly reported using leaf disc in vitro testing and foliage field assessment, or upon leaf and cluster field evaluations. In the current study, 28 grapevine hybrid cultivars were screened using leaf disc bioassay, for disease resistance characterization of both existing and wild-collected materials. 16 hybrids were identified as highly resistant or resistant, and will serve as relevant resistance donors in future pre-breeding and breeding programs. All grapevine hybrids were evaluated for foliar and cluster downy mildew resistance in an untreated field trial over three successive years. This study showed that the leaf disc bioassay provided some information on the resistance level of the genotypes under scrutiny, but it was a weak predictor of their resistance level under field conditions on leaves and even more on bunches. These findings are relevant to future applications in both traditional and marker-assisted breeding programs which promote sustainable viticulture.

Grapevine breeding programs in Italy

Abstract Grapevine breeding has been actively conducted in Italy since the end of the nineteenth century, producing approximately 800 varieties (rootstocks, wine and table grapes). The major Italian rootstock, wine and table grape breeders are listed, including the main varieties they obtained, such as Pirovano (cv. Italia), Paulsen (1103P rootstock), Dalmasso (cv. Albarossa), Ruggeri (140Ru rootstock), Prosperi (cv. Clotilde Prosperi), Manzoni (cv. Manzoni bianco), Terzi (cv. Incrocio Terzi 1) and Rigotti (cv. Rebo). Current breeding programs to obtain new rootstocks, new disease-resistant varieties and crossings within Vitis vinifera cvs. to improve some technological traits are described.