Recovery and sanitary selection of local vines of the Sardinia

A study was made on the recovery genotypes local grapevine with the aim to conserve them and to evaluate their health status and thus to improve the quality of the propagation material. Clone accessions of 61 vines were grafted and placed in a germoplasma field. The varieties that were considered enologically valuable were subjected to sanitary selection. Some vines showed indubitable healthy qualities, and should be immediately evaluated from an economical point view and then certificated. Possible sanitation treatments were also evaluated, with the aim of extending the number clone accessions to be included in experimental trials to access their yield

Molecular analysis of grapevine Pinot gris virus and its association with grapevine leaf mottling and deformation on 'Vermentino' grapevines in Sardinia

In 2017–2018, grapevines of cultivar 'Vermentino' infected with grapevine Pinot gris virus (GPGV) in Sardinia, Italy, exhibited leaf symptoms of mosaic, chlorotic mottling, and curling, and stunted shoots. Disease incidence assessed in 2018 was greater (67%, 103 symptomatic plants out of 153 monitored) than in 2017 (26%, 40 of 153 plants). All symptomatic samples tested by RT-PCR were positive for GPGV in both years, while 70% (53 of 76) of the asymptomatic samples in 2017, and 42% (19 of 45) in 2018, were also positive for GPGV. Characterizing six GPGV isolates from 'Vermentino' by RT-PCR and sequencing of a genomic fragment covering the movement and coat protein genes showed high conservation at the nucleotide level (98.7% to 100.0%) among Sardinian isolates and isolates for which sequence information is available in GenBank. Phylogenetic analysis indicated that most Sardinian GPGV isolates grouped with other European isolates. This is the first characterization of GPGV in a Sardinian vineyard

Expression of grapevine leaf stripe disease foliar symptoms in four cultivars in relation to grapevine phenology and climatic conditions

Grapevine leaf stripe disease (GLSD) symptom expression was analysed in four vineyards and four cultivars, in Sardinia (Italy), taking into account ten-year annual and five-year monthly surveys. The cumulative incidence of symptomatic plants reached high values on Sauvignon blanc, Cabernet sauvignon and Cannonau (81.9, 79.4 and 66.5% respectively), but low on Merlot (25.1%). Symptoms appeared during or before the 50% flowering stage and maximum increments were assessed in June and partially in July. Annual incidence of foliar symptoms fluctuated in the ten years of the survey. Positive regressions were found between incidence of vines that exhibited foliar symptoms in year n but were symptomless in year n-1 and rain parameters in the 30 days after stabilization of mean temperature around 10°C, when colonization of pruning wounds begins. This relationship could suggest the involvement of new infections or re-infections on symptom expression in the following growth season. Significant regressions between incidence of vines that exhibited foliar symptoms in year n but were symptomless in the year n+1 and climatic parameters were also recorded. High temperatures and low rainfall in the period from pre-flowering to veraìson were conducive to a higher number of asymptomatic plants. Regarding monthly foliar symptoms evolution, an increase in temperature from 50% sprouting until June led to a greater number of new symptomatic plants. On the other hand, a smaller percentage of new symptomatic plants was associated with an increase in temperature from June to July, which may have influenced vine water balance and transport of toxins by the sap flow

Identification of grapevine virus G and grapevine virus H in Sardinia, Italy

Grapevine virus G (GVG) and grapevine virus H (GVH) (genus Vitivirus) are recently discovered viruses. Analysis of 38 samples from Sardinian grapevine cultivars for the presence of GVG and GVH was carried out using RT-PCR. All samples were also tested for grapevine Pinot gris virus (GPGV) using RT-PCR, and for grapevine leafroll virus -1, -2 and -3, grapevine virus A (GVA) and B (GVB), arabis mosaic virus (ArMV), grapevine fanleaf virus (GFLV) and grapevine fleck virus (GFkV) using multiplex RT-PCR. GVG was confirmed in four vines, and GVH was detected in only one sample. In phylogenetic analyses of the coat protein (CP) region, the Sardinian GVG isolates clustered separately from isolates from Croatia and New Zealand. The Sardinian GVH isolate clustered with most sequences from other countries, but with greater affinity to isolates from California (USA) for the CP region, whereas it clustered with isolates from Croatia in the RNA-dependent RNA polymerase (RdRp) region. In addition to GVG and GVH, many samples were coinfected with GVA, viruses from the leafroll complex, and GPGV. This is the first record of GVG and GVH occurring in Italy

Genetic variability, chemotype distribution, and aggressiveness of Fusarium culmorum on durum wheat in Tunisia

Fusarium culmorum is the most commonly reported root rot pathogen in Tunisian durum wheat. Isolates of the pathogen from four durum wheat growing areas in the north of Tunisia were analyzed for their chemotypes. Two chemotypes were detected at unequal abundance (96% of 3-ADON and 4% of NIV). Distribution of a SNP mutation located at the position 34 bp after the first exon of the EF-1α partial sequence was analysed, to verify whether the haplotype was specifically associated to Fusarium root rot. A and T haplotypes were homogeneously distributed in three different Tunisian regions (Mateur, Beja and Bousalem) but not for the region of Bizerte, from which greatest number of A haplotype strains were detected. The isolates were tested for their virulence under glasshouse conditions, and a mean of 91% of crown and root infection was observed. Chemotype influenced virulence, but there was no significant influence of the geographical origin or haplotype on virulence. The distribution of three inter simple sequence repeats (ISSR) was examined, to better understand the structure of F. culmorum populations in Tunisia. A total of 27 fragments were obtained with eight polymorphic bands. Cluster analysis showed a high level of similarity between isolates. Analysis of molecular variance confirmed that there was little genetic differentiation among F. culmorum strains from different locations

New findings on phytoplasmas-affected Auchenorrhyncha populations in Sardinian vineyards

Epidemiological research was carried out in two vineyards affected by "Bois noir" (BN). Auchenorrhyncha potential vectors of BN, were monitored periodically between May to November 2004 in a vineyard and between May to June 2005 in the other. Auchenorrhyncha samples were tested to assess phytoplasmas presence using PCR and RFLP. Euscelis lineolatus was positive to 16SrI-C ("Clover phyllody" reference strain) in 2004 while, in 2005, at the preimaginal age, at the 16SrXII-A ("Stolbur" reference strain) phytoplasmas. Exitianus taeniaticeps acquired 16SrI-B ("Maryland aster yellow" reference strain), 16SrV-A ("Elm yellow" reference strain) and 16SrX-C ("Pear decline" reference strain) phytoplasmas in 2004. Resulted news host of phytoplasmas: Psammotettix alienus was positive to 16SrI-B, 16SrV-A, 16SrX-A phytoplasmas ("Apple proliferation" reference strain) in 2004 and to 16SrXII-A in 2005. E. lineolatus and P. alienus for 16SrXII-A E. taeniaticeps for 16SrV-A 16SrX-C and P. alienus for 16SrV-A and 16SrX-A Researches on the effective epidemiological role of E. lineolatus and P. alienus in BN are in progress. \ua92006 IEEE

Inter-laboratory validation of PCR-based protocol for detection of olive viruses

Sanitary selection and certification of olive cultivars require sensitive diagnostic methods and effective sanitation protocols. Although much attention has been paid in the past few years to the development of diagnostic tools for reliable virus identification, the need to define a common and standardized diagnostic protocol led to the implementation of a ring test among nine Italian diagnostic laboratories. A one-step RT-PCR protocol and different primer sets, targeting the most common olive viruses covered by phytosanitary rules, were tested in each laboratory, using the same batch of positive and healthy controls as well as the same amplification conditions and reaction components. The one-step RT-PCR, performed using several specific primer sets, was able efficiently to detect the target viruses in all laboratories. Furthermore, a one-step RT-PCR protocol was used successfully for the first time for detection of Tobacco necrosis virus (TNV) and Olive mild mosaic virus (OMMV). Results showed that all target viruses were not uniformly distributed in the canopy, and that at least two subsets of samples must be collected from each plant. This standardized protocol is now being used to produce nuclear stocks for 70 different Italian olive cultivars, in the framework of the national project OLVIVA, which involves 25 national research institutions