1,721,121 research outputs found
Atti Giornate Fitopatologiche 2016 - Protezione delle piante, qualità, ambiente
No full textSi tratta di due volumi sia stampati che distribuiti in forma elettronica relativi al Congresso nazionale 2016 Giornate Fitopatologiche (cadenza biennale) - I due curatori seguono l'intera produzione dei contributi riportati: dall'invio delle bozze da parte degli autori fino alla stesura definitiva organizzando l'intero processo di correzione, verifica e invio alla stampa coadiuvati da un comitato scientifico
EFFECTIVENESS DIFFERENCES OF CARBOXYLIC ACID AMIDES FUNGICIDES TOWARDS PLASMOPARA VITICOLA POPULATIONS: IN VIVO TESTS AND MOLECULAR STUDIES ON PVCESA3 GENE
No full textPlasmopara viticola is controlled by fungicides with different modes of action,including
carboxylic acid amides (CAAs). Dimethomorph was the first CAA introduced in 1988,
followed by iprovalicarb, flumorph, benthiavalicarb, mandipropamid, valifenalate and latest
pyrimorph in 2010
. The mode of action of CAAs is linked to the inhibition of cellulose synthesis
in the Oomycete plant pathogens. The mutations conferring CAA resistance in Plasmopara
viticola located on the CesA3 gene are G1105S and G1105V.The aim of this work was to
evaluate the activity of dimethomorph and mandipropamid on P. viticola populations.
Bioassays on leaf discs, and on seedlings were carried out. In leaf discs assay, CAAs tested on
Italian populations showed different level of activity and in particular dimethomorph showed
lower levels of EC95 and this behavior was also confirmed from seedling tests.
All CAA resistant populations carried the G1105S/V mutations, which were detected by RFLPPCR
and qPCR . In order to gain a better understanding of the different behavior and to define
the possible different resistant mechanism, molecular modelling and docking studies are
ongoing
First Report of Resistance to Cyflufenamid in Podosphaera xanthii, Causal Agent of Powdery Mildew, from Melon and Zucchini Fields in Italy
No full textThe fungicide cyflufenamid (phenyl-acetamide, Fungicide Resistance Action Committee [FRAC] code U6) was approved for use in Italy in 2011 as Takumi (Certis Europe, Utrecht, The Netherlands) to control Podosphaera xanthii (Castagne) U. Braun. & N. Shishkoff, the main causal agent of cucurbit powdery mildew. Considering that strains of this pathogen have developed resistance to strobilurin (5) and demethylation inhibitor (DMI) (4) fungicides, cyflufenamid represented a viable alternative to control this disease. However, this fungicide is also prone to resistance development as illustrated by resistance of P. xanthii in Japan (3). In the 2012 and 2013 growing seasons, significant declines in cyflufenamid efficacy were observed in two experimental fields in the Apulia (AP) and Emilia-Romagna (ER) regions of Italy on Cucumis melo and Cucurbita pepo, respectively. Takumi had been applied four times at the recommended field rate of 0.15 liter/ha (15 μg/ml of active ingredient [a.i.]) each growing season since 2010 in each field. Powdery mildew-infected leaf samples were collected in 2012 from both fields (25 isolates from AP and 19 from ER), and from five gardens (one isolate per garden); while in 2013, samples were collected only from the ER field (two polyconidial isolates). Isolates were maintained on detached zucchini cotyledons (1). Sensitivity of the isolates to cyflufenamid was determined by leaf disk bioassays (4) using Takumi at 0.01, 0.1, 1, 10, 20, and 50 μg a.i./ml. The 50% effective concentration (EC50) and the minimum inhibitory concentration (MIC) values were calculated (2). Isolates collected in ER and the gardens in 2012 all had an EC5050 μg/ml, and MIC values from 50 μg/ml; by 2013, the EC50 values of ER isolates ranged from 3.35 to >50 μg/ml. Based on the mean EC50 value of 0.0019 μg/ml for sensitive isolates of P. xanthii in Japan (2), isolates from both the ER field and gardens in 2012 were considered sensitive to cyflufenamid. Additionally, EC50 values of AP isolates from 2012 and ER isolates from 2013 were greater than those of sensitive isolates, indicating a shift in sensitivity toward resistance to cyflufenamid (resistance factor >100 [2]). Consequently, poor control of powdery mildew with cyflufenamid applications in the AP and ER trials was most likely a result of fungicide resistance. Isolates from these fields were exposed to selection pressure for fungicide resistance because cyflufenamid was applied more times than permitted in the label instructions. However, control of powdery mildew in 2013 was not as effective as in previous years in commercial fields in AP (C. Dongiovanni, personal communication). This observation, combined with proof of reduced sensitivity of some P. xanthii strains in Italy to cyflufenamid, highlights the need for implementing resistance management strategies to minimize the risk of fungicide resistant strains developing in cucurbit fields.
References: (1) B. Álvarez and J. A. Torés. Bol. San. Veg. Plagas 23:283, 1997. (2) M. Haramoto et al. J. Pest. Sci. 31:397, 2006. (3) H. Hosokawa et al. Jpn. J. Phytopathol. 72:260, 2006. (4) M. T. McGrath et al. Plant Dis. 80:697, 1996. (5) M. T. McGrath and N. Shishkoff. Plant. Dis. 87:1007, 2003
Screening of sensitivity to mandipropamid of Plasmopara viticola populations from Italian vineyards by molecular and biological methods
No full textWe characterized Plasmopara viticola populations utilizing PCRRFLP
technique to detect a point mutation known to cause resistance to carboxylic acid amides (CAA)
fungicides. Sensitivity of these samples to the mandipropamid fungicide was assayed by a leaf-disc
method. In this work, we provide the first evidence about the presence of mandipropamid-resistant
populations of P. viticola from commercial vineyards in Italy. Improving the knowledge about development
of resistant populations could enhance the current grapevine downy mildew management strategies
and minimize the risk of the spread of mandipropamid and other CAA-resistant populations
PRELIMINARY RESULTS OF STROBILURIN SENSITIVITY OF ZYMOSEPTORIA TRITICI ITALIAN STRAINS
No full textMycosphaerella graminicola (anamorph: Zymoseptoria tritici) is the causal agent of leaf blotch, the most important foliar disease of wheat in Northern and Central Europe. In Italy only during the last few years, the incidence of the disease has been increased.
The most common strategies for the control of the disease is the use of fungicides in particular QoIs, DMIs, and more recently were introduced the SDHIs. The resistance to QoIs and DMIs was already common in the main wheat cultivated areas in the world (Cools and Fraaije, 2008; Estep et al., 2015; Fraaije et al., 2005; Gisi et al., 2005; Leroux et al., 2005; Stammler and Semar, 2011; Stewart et al., 2014) while in Italy no results coming from wide and specific sensitivity monitoring are available. The aim of this study was to test the sensitivity of Z. tritici strains to QoI in order to obtain the first data about the Italian scenario.
Leaves of bread and durum wheat were collected during 2015 from 10 fields with different use of fungicides (wild type, experimental centers and commercial ones) located in the North of Italy. The sensitivity of 60 isolates to azoxystrobin at different concentrations (0-0.001-0.01-0.1-1-2-10-20 mg/L of active ingredient) have been determined in vitro by microtiter assay (Stammler and Semar, 2011).
The EC50 values of the wild types ranged from 0.02 to 0.12 mg/L of azoxystrobin, while the first analyzed isolates collected from experimental plots and commercial fields showed EC50s variable from 1.92 to 5.1 mg/L. Only one isolate pointed out an EC50 of 20.6 mg/L of active ingredient.
On the base of these first results, we can suppose the presence of a slight decrease of sensitivity of Z. tritici isolates collected from Italian fields (according to Gisi et al., 2005). Molecular analysis on the presence of G143A substitution will be carried out
EFFICACY OF CARBOXYLIC ACID AMIDES (CAA) FUNGICIDES TOWARDS CAA SENSITIVE and CAA RESISTANT PLASMOPARA VITICOLA POPULATIONS: IN VIVO TESTS AND MOLECULAR STUDIES ON PVCESA3 GENE
No full textPlasmopara viticola is controlled by fungicides with different modes of action, including carboxylic acid amides (CAAs). Dimethomorph was the first CAA introduced in 1988, followed by iprovalicarb, flumorph, benthiavalicarb, mandipropamid, valifenalate and latest pyrimorph in 2010 (Gisi et al. 2012). The mode of action of CAA compounds is linked to the inhibition of cellulose synthesis in the Oomycete plant pathogens. The mutations conferring CAA resistance in P. viticola located on the CesA3 gene are G1105S and G1105V.The aim of this work was to evaluate the activity of CAAs on CAA sensitive and CAA resistant isolates of Plasmopara viticola. Bioassays on leaf discs, on detached leaf and on grape plants trials were carried out. In leaf discs assay, CAAs tested on Italian strains showed different level of activity and in particular dimethomorph showed lower levels of EC95. The detached leaf tests showed under preventative conditions that the CAA-sensitive strains were fully controlled by all CAAs, while the CAA-resistant strains were best controlled by dimethomorph (Nanni et al. 2015). Under curative conditions all CAAs showed good activity on the sensitive strains, while the resistant strains were not controlled by any CAA. This finding confirms the cross resistance between CAAs. The good activity of dimethomorph on CAA resistant isolates under preventive conditions was also confirmed in greenhouse tests where whole plants were inoculated. All CAA resistant strains carried the G1105S/V mutations, which were detected by molecular techniques such as pyrosequencing, CAPS-PCR or qPCR. In order to gain a better understanding of the different behaviour among the CAA fungicides, molecular modelling and docking studies are still ongoing
Greenhouse assays on the control of the bacterial canker of kiwifruit (Pseudomonas syringae pv. actinidiae)
No full textBACKGROUND: Pseudomonas syringae pv. actinidiae (Psa) is the etiologic agent of the bacterial canker of kiwifruit, the most severe disease of Actinidia spp. This pathogen was firstly recorded in Japan and in China. The initial occurrence in Italy dates back to 1992, but the most important outbreak was in 2008. From that year, Psa has spread worldwide with a devastating virulence causing substantial losses to kiwifruit production in China, Italy, New Zealand, Chile, France and Portugal. OBJECTIVE: Screening the existing compounds with different mode of action for their efficacy in controlling Psa on Actinidia deliciosa (cv. Hayward) grown in controlled conditions. METHODS: Products were grouped according to their active ingredients and mode of action in the following categories: Copper compounds, plant extracts, disinfectants, resistance inducers, filming agents and biological control agents (BCAs). The experiments were performed on potted A. deliciosa (cv Hayward) vines grown in controlled greenhouse conditions. Inoculation was experimentally performed by spraying each plant till run off with a suspension of a highly virulent, biovar 3 Psa strain. Disease control and phytotoxicity were monitored for 15 and 30 days after inoculation. RESULTS: Copper compounds and resistance inducers (acibenzolar-S-methyl, Fosetyl-Al) showed the most promising results. However, few other compounds, such as some plant extracts and disinfectants (Verdeviva), provided some protection. Also biological control agents (BCAs), containing living microorganisms, partially controlled the disease. CONCLUSION: Copper compounds and resistance inducers can be possibly combined to develop a more robust and effective control strategy in open field. In addition, BCAs seem interesting, particularly in specific phenological stages when other control methods cannot be used, although results require further validation
First Report of Apple Bull’s Eye Rot Caused by Neofabraea malicorticis in Italy
No full textBull’s eye rot is an important postharvest disease affecting apples (Malus domestica)
worldwide. Fruit infection occurs in the field, but rot lesions develop only after a period in cold
storage (about 90 days). The disease is caused by fungi belonging to genus Neofabraea (N.
vagabunda, N. malicorticis, N. perennans, and N. kienholzii) (Spotts et al. 2009). However, no
data are available on the presence of species other than N. vagabunda in Italy. To verify the
current causal agents of apple bull’s eye rot in the Emilia-Romagna region, a pathogen survey
of apples stored in several local packinghouses and showing bull’s eye rot symptoms was
carried out in 2014 and the causative agents identified. Small sections from the edges of
rotten tissue of 100 fruits were placed on tomato agar (TA) and kept at 15°C. Sporulation was
observed after 14 days of incubation. Mycelia originated from the single spore of 20 isolates
were used for DNA extraction. PCR was used to amplify the β-tubulin (tub2) gene using
primers F 5′-CTTTCTCCGTTGTCCCATCC-3′ and R 5′-GAACATTGCGCATCTGGTCC-3′ (Cao et al.
2013). After sequencing and sequence assembly, BLAST analysis showed that one isolate (M1)
had 99% identity to N. malicorticis, while other isolates belonged to N. vagabunda. The
sequence of N. malicorticis isolate was submitted to GenBank (accession no. KP263368).
Morphological characteristics of N. malicorticis isolate were examined after 14 days of
incubation on TA at 15°C. Colonies were circular, centrally umbonate, with abundant white
floccose mycelium. Average growth rate was 22 ± 2 mm in 14 days. Conidia were one-celled,
cylindrical, rounded at apex, aseptate, hyaline, and measured 6 to 16 μm (mean 10 ± 2.4 μm)
× 2 to 5 μm (mean 3 ± 0.8 μm), similar to micro and intermediate conidia formed on oatmeal
(Chen et al. 2015). To prove pathogenicity, Koch’s postulates were conducted on 10 ‘Cripps
Pink’ apples, surface-sterilized, wounded, and inoculated with 20 μl conidial suspension (104
conidia ml–1). After 90 days of storage at 0°C, artificially infected apples showed lesions of 21
to 29 ± 1 mm diameter without conidiomata on peel surface (symptoms identical to those
observed on apples that were originally obtained from cold storage). Water-only controls were
symptomless. The pathogen was reisolated from decayed tissue. To our knowledge, this is the
first report of N. malicorticis causing bull’s eye rot of apples in Italy. This finding suggests that,
beside N. vagabunda, other species of Neofabraea may occur in Italy and this could represent
an emerging problem on apples. Epidemiological studies performed on a wider scale could
improve the knowledge of current Neofabraea species occurring in Italian orchards, leading to
the adoption of specific control strategies to reduce fruit postharvest losses
First Report of QoI Resistance in Venturia inaequalis Causing Apple Scab in Apple Orchards in Turkey
No full textApple scab caused by Venturia inaequalis (Cke.) Wint. is the most important disease of apple (Malus × domestica) in Turkey. To control apple scab, quinone outside inhibitor (QoI) fungicides have been used since 1998. Apple scab control failures were observed in 2005 in Mediterranean and Central Anatolian regions, where apple production is intensive and where QoIs have been applied in 3 or 4 consecutive applications per season from pink bud stage to half fruit size of apple trees. Ten field populations of V. inaequalis, each obtained from 40 to 50 infected leaves, were collected in orchards located in the aforementioned production regions in May 2011 to verify the sensitivity to QoI fungicides. Samples were obtained from one wild-type orchard which had never been treated with fungicides and was far away from the treated orchards, four orchards which had never been exposed to QoIs, and five orchards where QoIs control failures were observed. To obtain populations with high germinative energy, conidia were propagated on apple seedlings (cv. Golden) in greenhouse (Küng Färber et al. 2002). After 20 days of incubation, conidial suspension (1 to 3 × 105 spores/ml) was prepared from infected V. inaequlis leaves for the evaluation of spore germination on agar media amended with 0, 0.001, 0.01, 0.1, and 2 mg/liter of trifloxystrobin as technical grade (Sigma-Aldrich, St. Louis, MO) (Fiaccadori et al. 2011). Data were transformed into the 50% effective concentration (EC50) by probit analysis utilizing Microsoft Excel. Genomic DNA was extracted directly from lyophilised infected leaves ground in liquid nitrogen by a CTAB-based method and then purified through a Sepharose 6B (Bramwell et al. 1995). CAPS analyses were performed with two specific primers, ANK 10 and ANK 283, to amplify a 413-bp fragment of cytochrome b gene which includes the G143 codon following the protocol by Fiaccadori et al. 2011. qPCR was performed for the quantitative detection of the A143 allele using an ICycler-IQ5 (Bio-Rad) with SybrGreen (Bio-Rad) with the primer set both for the wild-type (FwS5418-Rv5548) and for the mutant allele (FwR5418-Rv5548) (Nanni et al. 2011). The ratio (%) of the two alleles present in samples was calculated using the ΔCq method according to the equation: 10^ (Cq S allele– Cq R allele)/-slope); R (R/1+R) × 100 = R allele. Data are expressed as a percentage of the mutated allele. The wild-type population had an EC50 value of 0.00001 mg/liter and the four untreated orchards showed EC50 values ranging from 0.004 to 0.04 mg/liter. These V. inaequalis orchard populations can be considered sensitive according to the baseline study (Küng Färber et al. 2002). qPCR detected R-allele frequencies ranging from 0.1 to 3.61% in these V. inaequalis populations, whereas G143A substitution was not detected by CAPS PCR because its detection limit is under 10% (Bäumler et al. 2003). The five populations obtained from orchards where poor control has been reported were defined as resistant, showing EC50 values ranging from 1.46 to >2 mg/liter. These populations exhibited the G143A substitution with a higher R-allele frequency, compared with the wild-type population, ranging from 46.62 to 99.76%. Consequently, practical resistance of V. inaequalis to QoI is present in some Turkish apple-growing areas. To our knowledge, this is the first report of practical QoI fungicide resistance and G143A detection in V. inaequalis in Turkey that led to limiting QoI use to one application per season in the sampled areas
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