Studio sulle specie di <i>Phytophthora</i> presenti in ambienti forestali della Sardegna

Phytophthora spp. are devastating plant pathogens in both agricultural and natural environments. Since little is known about the occurrence and spread of Phytophthora spp. in Sardinia, a survey was carried out in various forest ecosystems. Overall two chestnut groves, one oak stand, two riparian ecosystems and three forest nurseries were surveyed. Isolations were made directly from symptomatic plant tissues and using Rhododendron leaves and apples as bait. Molecular and morphological characterizations were used to identify the isolates. Aggressiveness of the Phytophthora isolates was assayed by different methods: soil infestation and stem inoculation of seedlings and by inoculating living logs. It was also evaluated the ability of some species to produce in vitro phytotoxic metabolites. The survey revealed the presence of 12 species of Phytophthora: P. cambivora, P. cinnamomi, P. cinnamomi var. parvispora, P. cryptogea, P. gonapodyides, P. ilicis, P. nicotianae, P. pseudosyryngae, P. taxon niederhauserii, P. taxon salixsoil, Phytophthora sp. 1 e Phytophthora sp. 2. In particular: P. cinnamomi var. parvispora, P. pseudosyringae and P. taxon niederhauserii were recorded in a new association host-pathogen in Italy. Another species, P. ilcis is here reported for the first time in a natural ecosystem in the Mediterranean basin

<i>Phytophthora</i>:an ancient, historic, biologically and structurally cohesive and evolutionarily successful generic concept in need of preservation

The considerable economic and social impact of the oomycete genus Phytophthora is well known. In response to evidence that all downy mildews (DMs) reside phylogenetically within Phytophthora, rendering Phytophthora paraphyletic, a proposal has been made to split the genus into multiple new genera. We have reviewed the status of the genus and its relationship to the DMs. Despite a substantial increase in the number of described species and improvements in molecular phylogeny the Phytophthora clade structure has remained stable since first demonstrated in 2000. Currently some 200 species are distributed across twelve major clades in a relatively tight monophyletic cluster. In our assessment of 196 species for twenty morphological and behavioural criteria the clades show good biological cohesion. Saprotrophy, necrotrophy and hemi-biotrophy of woody and non-woody roots, stems and foliage occurs across the clades. Phylogenetically less related clades often show strong phenotypic and behavioural similarities and no one clade or group of clades shows the synapomorphies that might justify a unique generic status. We propose the clades arose from the migration and worldwide radiation ~ 140 Mya (million years ago) of an ancestral Gondwanan Phytophthora population, resulting in geographic isolation and clade divergence through drift on the diverging continents combined with adaptation to local hosts, climatic zones and habitats. The extraordinary flexibility of the genus may account for its global ‘success’. The 20 genera of the obligately biotrophic, angiosperm-foliage specialised DMs evolved from Phytophthora at least twice via convergent evolution, making the DMs as a group polyphyletic and Phytophthora paraphyletic in cladistic terms. The long phylogenetic branches of the DMs indicate this occurred rather rapidly, via paraphyletic evolutionary ‘jumps’. Such paraphyly is common in successful organisms. The proposal to divide Phytophthora appears more a device to address the issue of the convergent evolution of the DMs than the structure of Phytophthora per se. We consider it non-Darwinian, putting the emphasis on the emergent groups (the DMs) rather than the progenitor (Phytophthora) and ignoring the evolutionary processes that gave rise to the divergence. Further, the generic concept currently applied to the DMs is narrower than that between some closely related Phytophthora species. Considering the biological and structural cohesion of Phytophthora, its historic and social impacts and its importance in scientific communication and biosecurity protocol, we recommend that the current broad generic concept is retained by the scientific community. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s43008-022-00097-z

First report of Neofusicoccum australe associated with grapevine cordon dieback in Italy

This is the first report of Neofusicoccum australe associated with grapevine dieback in Italy. Fungal isolates obtained from symptomatic tissues were identified on the basis of morphological and cultural characteristics as well as ITS sequence data. Pathogenicity was verified by inoculation of excised green grapevine shoots from cv. Cannonau under controlled laboratory condition

Rosmarinus officinalis L.: chemical modifications of the essential oil and evaluation of antioxidant and antimicrobial activity.

Rosmarinus officinalis essential oil was separated into its hydrocarbon and oxygenated fractions. The major compounds in the hydrocarbon fraction were α-pinene (44.2%), camphene (24.5%), and limonene (11.7%), while in the oxygenated fraction they were 1,8-cineole (37.6%), camphor (16.5%), and bornyl acetate (21.4%). The hydrocarbon fraction was submitted to a hydroformylation process and the antioxidant activity of the product was screened by the DPPH and β-carotene/linoleic acid tests. The hydroformylated fraction maintained the antioxidant activity of the whole oil. The MIC (minimal inhibitory concentration) and the MBC (minimal bactericidal concentration) of the essential oil, hydrocarbon, oxygenated and hydroformylated fractions were also tested on several microorganisms. Aeromonas sobria and Candida strains were the most susceptible micro-organisms. The hydroformylated fraction exhibited a MBC against Candida strains resistant to the other fractions

A survey in natural forest ecosystems of Vietnam reveals high diversity of both new and described Phytophthora taxa including P. ramorum

In 2016 and 2017, surveys of Phytophthora diversity were performed in 25 natural and semi-natural forest stands and 16 rivers in temperate and subtropical montane and tropical lowland regions of Vietnam. Using baiting assays from soil samples and rivers and direct isolations from naturally fallen leaves, 13 described species, five informally designated taxa and 21 previously unknown taxa of Phytophthora were isolated from 58 of the 91 soil samples (63.7%) taken from the rhizosphere of 52 of the 64 woody plant species sampled (81.3%) in 20 forest stands (83.7%), and from all rivers: P. capensis, P. citricola VII, VIII, IX, X and XI, P. sp. botryosa-like 2, P. sp. meadii-like 1 and 2, P. sp. tropicalis-like 2 and P. sp. multivesiculata-like 1 from Phytophthora major phylogenetic Clade 2; P. castaneae and P. heveae from Clade 5; P. chlamydospora, P. gregata, P. sp. bitahaiensis-like and P. sp. sylvatica-like 1, 2 and 3 from Clade 6; P. cinnamomi (Pc), P. parvispora, P. attenuata, P. sp. attenuata-like 1, 2 and 3 and P. ×heterohybrida from Clade 7; P. drechsleri, P. pseudocryptogea, P. ramorum (Pr) and P. sp. kelmania from Clade 8, P. macrochlamydospora, P. sp. ×insolita-like, P. sp. ×kunnunara-like, P. sp. ×virginiana-like s.l. and three new taxa, P. sp. quininea-like, P. sp. ×Grenada 3-like and P. sp. ×Peru 4-like, from Clade 9; and P. sp. gallica-like 1 and 2 from Clade 10. The A1 and A2 mating types of both Pc and Pr co-occurred. The A2 mating type of Pc was associated with severe dieback of montane forests in northern Vietnam. Most other Phytophthora species, including Pr, were not associated with obvious disease symptoms. It is concluded that (1) Vietnam is within the center of origin of most Phytophthora taxa found including Pc and Pr, and (2) Phytophthora clades 2, 5, 6, 7, 8, 9, and 10 are native to Indochina.info:eu-repo/semantics/publishedVersio

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

Principali avversità biotiche dell'eucalipto in Sardegna

Il genere Eucalyptus (fam. Mirtaceae) è originario dell'Oceania e include oltre 600 specie di alberi e arbusti sempreverdi. Nell'Italia centro meridionale la specie più diffusa è l'Eucalyptus camaldulensis Dhenh. La grave diffusione di fenomeni di deperimento e di moria di piante nei popolamenti di eucalipto della Sardegna ha richiesto indagini di carattere entomologico e patologico, condotte in 12 aree dell'Isola