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

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

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

<em>In Vitro</em> Cultures for the Production of Secondary Metabolites

Plants’ secondary metabolism is an important source of medicinal and industrial products. Even though natural ecosystems are still the most important font of this kind of substance, excessive harvesting of spontaneous flora can act as a direct cause of biodiversity loss. Different technologies are used for in vitro production which, in addition to being useful for safeguarding biodiversity, make available to industry substances that are difficult to produce in vivo. Moreover, the growing demand for secondary metabolites encourages the use of new biotechnology tools to create new, more productive in vitro transgenic plant cultures