Indagine sanitaria relativa alla presenza di patogeni di nuova introduzione in Sardegna

My work was focused on the detection of some new pathogens in Sardinia, namely: Grapevine Pinot gris virus (GPGV) and Grapevine asteroid mosaic virus (GAMaV) affecing grapevine and Olpidium spp. fungal pathogens on curcubits.In the first chapter, I report the results of a monitoring conducted in Sardinia and Lazio regions in 2016, aiming to detect vineyards manifesting Grapevine leaf mottling and deformation (GLMD) disease. A total of 195 grapevine samples were examined in the two regions; 54 samples were collected from different areas and cultivars in Sardinia. GPGV was identified as responsible of GLMD for the first time in Sardinia and Lazio. GPGV was ascertained in all symptomatic but also in some asymptomatic samples. About 28% of the total analysed (52) samples tested positive for GPGV; this number increases up to 54% (28 samples) if we consider only the samples taken in Sardinia. The virus was not detected in samples from vineyards older than 10 years and/or planted with local cultivars, with a few exceptions.In the third chapter, investigations on GLMD and GPGV continued in a Vermentino vineyard severely affected by the disease. For this purpose, 154 samples were collected in 2017 and 2018. Samples were classified into three categories based on the symptoms: symptomatic, asymptomatic and showing other symptoms. During the 2-years survey, all symptomatic samples tested for the presence/absence of GPGV were positive, and also 52% of the asymptomatic ones. Furthermore, the number of positive samples collected from symptomatic plants was much higher in 2018 than in 2017, as many of the asymptomatic, but GPGV positive plants sampled in 2017 showed symptoms in 2018. A blast analysis of movement protein (MP) and coat protein (CP) sequences from Sardinian isolates showed a high identity level (between 98.67 and 100%) with sequences deposited in GenBank. Both MP and CP phylogenetic trees showed that most CP and MP sequences are grouped within the European strain clade. The third chapter reports the first detection of GAMaV in Italy. Analysis of the grapevine genome revealed the presence of sequences belonging to the GAMaV in four Cannonau cv plants. This was confirmed by the amplification of the RNA extracted from berries with specific primers. No detectable symptoms were observed in any of the infected vines, hence supporting the hypothesis that GAMaV may be largely latent or semilatent.Chapters 4 and 5 report for the first time in Italy the occurence of Olpidium virulentus and O. bornovanus on watermelon and of O. virulentus, O. bornovanus and O. brassicae on cucumber. This is the result of a monitoring conducted on watermelon and cucumber in northern Sardinia, where plants with symptoms of "collapse", usually attributed to Melon necrotic spot virus or Monosporascus spp., were reported. Symptomatic plants were sampled together with infected soil adjacent to symptomatic roots. Pathogenicity tests carried out in greenhouses using infected soil reproduced symptoms observed in the field. Olpidium species were identified by using morphological and molecular methods.