Alberto Materazzi

Survival of Sclerotinia minor Jagger sclerotia in solarized soil

Soil solarization reduced both recovery and viability ofSclerotinia minor sclerotia depending on the depth of burial. Highest reduction of these parameters was obtained at 4–6 cm depth (55%) and 0–2 cm depth (96%) respectively. Soil solarization accelerated the exponential decay of sclerotia observed in natural soil. In the upper 6 cm of soil this decay was so fast that after about 14 days loss of the sclerotial viability approached values recorded at the end of the treatment after 41 days. The number of sclerotia colonized by microorganisms is higher in solarized than in non-solarized plots.

RFID temperature sensors for monitoring soil solarization with biodegradable films

RFID sensors are effective for real-time temperature monitoring during solarization.Lesions of biodegradable film can be highlighted by RFID temperature assessment.Easy-to-use monitoring tools help the farmer to understand the thermal effect. Soil-borne pathogen and weed control can be achieved by soil solarization even if estimation of time treatment is difficult to assess. Thus, due to dependence to environmental conditions and the need to minimize the time of treatments, the implementation of monitoring tools may help in solarization managements, especially when biodegradable films were applied or weather condition are subjected to significant variation. Digitalization of data relative to plants thanks to RFID applications has been used for health or treatment monitoring, sample collecting and retrieving sanitary information: this paper presents the testing of RFID sensor application for soil solarization purposes. Different matrices were selected to assess RFID temperature sensors performances. Sandy, loam and clay soils with different moisture-holding capacity were selected for sensor burial. Sensors were covered by 5 or 10cm of fresh matrix and read immediately. Reliability was found to be more than 90% in all tested conditions, while higher failure in tag reading was recorded in clay soil at 90% of moisture-holding capacity (-7% of tag reliability). Soil solarization treatment was carried out as case of study during a period characterized by changeable weather using a biodegradable film. Data, expressed as thermal addition and temperature classes, collected continuously by sensors permitted to design real-time graphs that help the farmer to understand the thermal effect caused by treatment. Throughout the second and third week of treatments, Tmax at 5cm depth is increased by 9-13?C or 11-14?C compared to environment, respectively. Otherwise, Tmax at 10cm depth is increased by 7-9?C compared to environment throughout the second and third week, showing as sensors are able to collect temperature during solarization. The soil microbial community of soils treated with solarization exhibited a slight reduction of cumulative carbon metabolic activity compared to control (8.8% of reduction), while among 31 preselected carbon sources, the soil microbial communities were capable of utilizing up to 23 carbon source without difference between treatments. Unified Modeling Language activity diagrams for solarization management via digital sensors were designed and effects of biodegradable film on microbial population were observed. The integration of information technology solutions with new-generation biodegradable films may offer an interesting revaluation of soil solarization in actual farm organization.

Control of Soil-Borne Diseases in Tomato by Use of Steam and an Exothermic Reaction

In 2005-2006 we tested pre-planting treatments applied using a self-propelled soil steaming machine designed for the release of steam after incorporation in the soil of a substance that causes an exothermic reaction able to heat it to a mild but effective temperature x time product. Experiments were conducted in open-field conditions by assessing the effectiveness of steam and potassium hydroxide (KOH) against Fusarium oxysporum f.sp. lycopersici and Sclerotium rolfsii on tomato plants. The combination of steam and exothermic reaction chemicals reduced the incidence of Fusarium wilt (93.4-94.8%) better than steam only (77.8-81.2%); control of Sclerotium rolfsii was likewise better with KOH (86.7-87.7%) than with steam only (65.0-71.0%). The effects of treatments on microbial density, plant growth and weed control were evaluated. Treatments caused significant reductions in the number of Fusarium oxysporum colonies compared to the untreated control, an increase in Trichoderma spp. and no significant effects on total fungus and actinomycete density. Significant reduction in weeds (above 82.5%) and drastic increase in plant growth was recorded with the use of steam/exothermic reaction. With a milder steam application, the exothermic reaction acts for a slight increase in Tmax and, most of all, on time in temperature x time product, obtaining a disease control similar to drastic steam treatments.

FIRST REPORT OF ZANTEDESCHIA MILD MOSAIC VIRUS ON ZANTEDESCHIA AETHIOPICA (L) SPRENG IN ITALY

Calla lily [Zantedeschia aethiopica (L.) Spreng] has become one of the most popular cut flowers worldwide. It has been reported as the natural host of various plant viruses, including potyviruses such as Bean yellow mosaic virus (BYMV), Dasheen mosaic virus (DsMV), Turnip mosaic virus (TuMV) and Zantedeschia mosaic virus (ZaMV). In 2005 a new potyvirus named Zantedeschia mild mosaic virus (ZaMMV) was identified in Taiwan (Huang and Chang, 2005). In 2012, 15 plants of Calla lily cultivated in Tuscan farms showed leaves with yellow spots and stripes, green islands and an unusual mild mosaic. Seventeen samples (15 symptomatic and two symptomless) were collected and assayed by ELISA for BYMV, DsMV, TuMV, ZaMV and potyviruses using antisera produced by DSMZ (Braunschweig, Germany) and LOEWE Biochemica (Sauerlach, Germany). Plants were positive for an anti-potyvirus group monoclonal antibody. Positive samples were assayed by reverse transcription-polymerase chain reaction for ZaMMV using total RNA extracted from leaves and specific primers for the coat protein gene (Wen-Chi et al., 2010). Amplicons of the expected size (792 bp) were obtained for 15 samples that reacted positively to the potyvirus antibodies, while no amplification was observed in symptomless samples. The sequence obtained from one ZaMMV amplicon (accession No. KF156666) had 99% nucleotide identity with the corresponding fragment of a reference ZaMMV isolate (GenBank accession no. AY626825.4). To our knowledge this is the first report of ZaMMV on Zantedeschia aethiopica in Italy.

Electronic identification systems for reducing diagnostic workloads after disease outbreak

Diagnostic tests for grapevine viruses subjected to phytosanitary rules involve a heavy workload for plant protection services and laboratories. Propagation schemes enable nurseries, where mother plants (MPs) are cultivated, to be linked to batches of certified plants (CPs). This approach entails post-production checks of MPs once infection occurs in CPs. However, this traceability system is not tight and follow ups are demanding. This study assessed radio frequency identification (RFID) tagging of plants in terms of its ability to reduce laboratory workloads for nursery health checks. RFID-tagged plants (RFID-CPs) were produced from individually tagged MPs (RFID-MPs) or row-tagged MPs (RFID-ROW, a less expensive approach). In a 10-year case study, the health status of CPs and RFID-CPs were assessed and the occurrence of infections then led to health checks in MPs, RFID-MPs or RFID-ROWs. Laboratory workloads were evaluated by considering two sampling methods (single or pool sampling). Using single sampling, the workload was reduced by 93–98% in RFID-ROW or RFID-MP checks compared to the conventional approach. Considerable reductions in workload due to the tagging system (93–96%) were also observed using pool sampling. Traceability of CPs and MPs using RFID reduces laboratory workloads, and supports emergency measures that can be taken to stop any unsafe sales of plants after a virus outbreak.

Phylogenetic analysis of viruses in Tuscan Vitis vinifera sylvestris (Gmeli) Hegi

The health status of the native grapevine Vitis vinifera subsp. sylvestris (Gmeli) Hegi in natural areas in Europe has received little attention. A survey was carried out on wild grapevines in Tuscany (Italy), where isolates of the Grapevine rupestris stem pitting virus (GRSPaV), Grapevine leafroll-associated virus 1 and 3 (GLRaV-1 and GLRaV-3) and Grapevine virus A (GVA) were detected. The complete coat protein (CP) region of these isolates was sequenced to investigate the relationship of the viral variants from Tuscan wild grapevines with isolates from different geographical origins. According to the phylogenetic analyses, GLRaV-1 and GLRaV-3 isolates from Tuscan wild grapevines clustered with isolates from cultivated grapevines with nucleotide sequence identities ranging from 66% to 87% and from 72.5% to 99% respectively, without any correlation between the distribution and geographical origin. Conversely, GRSPaV and GVA isolates clustered together with other Italian isolates from V. vinifera with nucleotide sequence identities ranging from 71.14% to 96.12% and from 73.5% to 92%, respectively. Our analysis of the whole amino acid sequences revealed a high conservation level for the studied proteins explained by a selective pressure on this genomic region, probably due to functional constraints imposed on CP, such as specific interactions with cellular receptors in the insect vectors necessary for successful transmission. In addition, analyses of genetic recombination suggest no significant point mutations that might play a significant role in genetic diversification. The dN/dS ratio also estimated a low number of non-silent mutations, highlighting the purifying selective pressure. The widespread distribution of the Rugose wood complex (GRSPaV and GVA associated disease) in comparison with the Grapevine Leafroll associated viruses (GLRaV-1 and -3) could explain the major geographical correlation found for the viral variants detected in Tuscany.

Prevalence of a ‘Candidatus Phytoplasma solani’ strain, so far associated only with other hosts, in Bois Noir-affected grapevines within Tuscan vineyards

Due to its complex epidemiological cycle, including several polyphagous insect vectors and host plants, and the absence of efficient control strategies, Bois Noir (BN) disease of grapevine is encroaching wider territories in the main viticultural areas worldwide. Molecular approaches allowed to increase the knowledge about its etiological agent (Bois Noir phytoplasma, BNp; ‘Candidatus Phytoplasma solani’ species), revealing interesting features concerning BNp population structure and dynamics and transmission routes in vineyard agro‐ecosystems. In the present study, a multilocus sequence typing approach (vmp1 and stamp genes) was utilised for describing the genetic diversity among BNp strain populations in 17 vineyards localised in two distinct geographic areas in Tuscany (central Italy). The results confirmed that BNp ecology in Tuscan vineyards is mainly associated to the bindweed‐related host system, and allowed the identification of 14 BNp vmp1/stamp genotypes. Interestingly, the prevalent genotype (Vm43/St10) was never found in grapevines outside of Tuscany. Moreover, statistical analyses showed significant differences between the composition of BNp strain populations identified in grapevines from north‐western and central‐eastern Tuscany. These results reinforce the hypothesis that distinct geographic areas, probably associated with different ecological niches, can drive the selection of BNp strains, also favouring the entrance of unusual ‘Ca. Phytoplasma solani’ genotypes in vineyards.

Genotyping of Grapevine Varieties from Garfagnana (Northern Tuscany): Evidence of a Historical Center of Diversity

The aim of this investigation was to recover, characterize, and increase the value of local grapevine varieties from Garfagnana, a mountainous area situated in the north of Tuscany (located in central Italy). A total of 130 accessions (vines) were identified in old Garfagnana vineyards, characterized by Organisation Internationale de la Vigne et du Vin morphological-phenological and productive parameters, and genotyped with 14 microsatellite loci. The microsatellite analysis identified 50 genotypes. Some of these genotypes matched Tuscan genotypes, others corresponded to varieties cultivated in other Italian and European regions, and 18 appeared to be genotypes currently identified only in Garfagnana and presumably autochthonous to this area. Cluster and similarity analyses based on both microsatellite and morphology data indicated a clear grouping of the majority of the autochthonous genotypes from Garfagnana. A parentage analysis revealed that the Garfagnana autochthonous genotypes are highly first degree–related among each other, suggesting that Garfagnana is a distinct historical center of diversity of cultivated varieties. The data from all varieties have been entered into the Italian Vitis Database (www.vitisdb.it).

FIRST REPORT OF GRAPEVINE LEAFROLL ASSOCIATED VIRUS-4 STRAIN 5 IN ITALY

Leafroll is one of the most harmful viral diseases affecting grapevine worldwide. Historically, a dozen of viruses, named grapevine leafroll-associated viruses (GLRaVs), belonging to genera Closterovirus and Ampelovirus (Family Closteroviridae), have been found associated with the disease. Recent studies showed that GLRaV-4, -5, -6, -Pr, De- and -Car are in fact strains of the same virus species (Abou Ghanem-Sabanadzovic et al., 2012) prompting taxonomic and nomenclatural revision of these viruses. Among these viruses, GLRaV-4 strain 5 has been reported from many viticultural areas in the world. In 2012-2013, surveys for virus detection disclosed the identification of GLRaV-4 strain 5 in 768 samples collected in Tuscany. The virus presence was ascertained by real-time (RT)-PCR as reported by Osman et al. (2007). GLRaV-4 strain 5 was found in 2 samples (0.63 % rate, 2012) and in 4 samples (1.16 %, 2013) in cvs Sangiovese and Canaiolo. Further molecular analysis revealed that one-infected vine hosted a single GLRaV-5 infection, while other infected vines were infected with multiple viruses, including GLRaV-3, GVA, GFkV and GRSPaV. The GLRaV-4 strain 5 sequences obtained from the positive samples shared 96% nucleotide identities with the corresponding fragment of a reference GLRaV-5 isolate (GenBank accession No. JX559639.1). The nucleotide sequence was deposited in GenBank as accession No. KM252726. To the best of our knowledge this is the first report of the occurrence of GLRaV-4 strain 5 in Italian vineyards.

Grapevine Vein Necrosis: Further Data on Etiology and Diagnosis

Vein necrosis (VN), a virus-like disease latent in all European grapevine cultivars and in most American rootstock species and hybrids, induces necrosis of the veinlets on its specific indicator Vitis rupestris times Vitis berlandieri 110 R. Vein necrosis is very common in Tuscany, where, during an indexing trial, 38 out of 62 (61%) putative grapevine clones selected during sanitary improvement programmes in the last few years indexed positive on 110 Richter. The 62 accessions were checked by PCR with two different universal primers (13/14 and RSP5/RSP6) for the presence of Grapevine rupestris stem pitting-associated virus (GRSPaV) and with group specific primers (Groups I, II and III). Primers 5/6 were able to detect all sequence variants and a differential biological behavior was observed among molecular variants. Only group I was highly associated to symptoms expression, groups II an III were not correlated to vein necrosis.