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In recent years, an unusual decline and mortality has been observed in Paulownia plantations throughout the Marche region (Central Italy). Given the economic importance of this emerging forest crop, a study was conducted to determine which pathogens are directly involved in this syndrome. Field surveys performed in two plantations revealed the widespread occurrence of severe disease symptoms such as leaf chlorosis, crown thinning, shoot and branch dieback, sunken cankers, epicormic shoots and root rot. Disease incidence was also assessed by aerial remote sensing (RS) technologies using drones. Symptomatic samples collected from both stem and root tissues yielded fungal and fungal-like colonies representing two distinct families: Botryosphaeriaceae and Peronosporaceae. Morphological and DNA sequence data revealed five distinct species, identified as Macrophomina phaseolina and Botryosphaeria dothidea (Botryosphaeriaceae), Phytophthora pseudocryptogea, P. citrophthora and P. erythroseptica (Peronosporaceae). Given that all species are reported here for the first time on Paulownia, Koch's postulates were satisfied inoculating the three Phytophthora species and two Botryosphaeriaceae at the collar of the stem of potted 1-year-old rooted cuttings in June 2023. Thirty days after inoculation, all plants showed the same symptoms as those observed in the field. [ABSTRACT FROM AUTHOR]

The rapid growth and environmental adaptability of Eucalyptus species has favored their global cultivation for pulpwood production. On the island of Sardinia, Italy, eucalypt plantations were established in the 20th century primarily in areas reclaimed from marshland, but the trees are now grown all over the island as ornamentals or windbreaks, and for timber, pulp and honey production. In recent years, an unusual decline and mortality of unknown etiology has been observed in Eucalyptus camaldulensis (river red gum) plantations throughout the island. Given the ecological and economic importance of eucalypt ecosystems in Sardinia, a survey was carried out in 2013 to determine which insect pests and fungal pathogens are directly involved in these phenomena. Field surveys throughout the island revealed severe infestations with the red gum lerp psyllid (Glycaspis brimblecombei) at all 12 surveyed sites, with the greatest numbers of pre-imaginal stages and adults occurring between May and July. The adult population reached its peak in July, followed 2 months later by the peak population of its specific parasitoid, Psyllaephagus bliteus. Symptoms of leaf chlorosis, crown thinning, shoot and branch dieback, sunken cankers, epicormic shoots and exudations of kino gum were also observed at the 12 field sites. Symptomatic woody samples yielded fungal isolates representing three distinct families: Botryosphaeriaceae, Diaporthaceae and Valsaceae. Morphological and DNA sequence data revealed seven distinct fungal species, namely Diaporthe foeniculina, Neofusicoccum australe, N. luteum, N. mediterraneum, N. parvum, N. vitifusiforme and Valsa fabianae. Two putative new species of Cytospora were also identified. Neofusicoccum australe was the only species recovered from all 12 sites, with isolation frequencies of 51-95%. Pathogenicity trials revealed that all Neofusicoccum species except N. vitifusiforme are directly involved in the etiology of the observed decline in the E. camaldulensis population on Sardinia.

A cork oak endophytic strain of Trichoderma citrinoviride, previously selected for its antagonistic potential against various fungal pathogens involved in oak decline, was screened for the production of bioactive secondary metabolites. From liquid culture a mixture of polypeptide antibiotics (peptaibols) belonging to the paracelsin family was isolated and characterized. This peptide mixture was purified by column chromatography and preparative TLC on silica gel, and separated by analytical HPLC. It was analysed by MALDI-TOF MS and nano-ESI-QTOF MS. Tandem mass experiments were performed to determine the amino acid sequences based on the fragmentation pattern of selected parent ions. The mixture comprised 20-residue peptides with C-terminal phenylalaninol and N-terminal acetylation. Twenty-eight amino acid sequences were identified, and amino acid exchanges were located in positions 6, 9, 12 and 17. Among them, seven sequences are new as compared to those reported in the database specifically for peptaibols and in the literature. In addition, we obtained experimental evidence suggesting the existence of non-covalent dimeric forms (homo-and hetero-) of the various peptaibol species. The peptide mixture showed strong antifungal activity toward seven important forest tree pathogens, and it was highly toxic in an Artemia salina (brine shrimp) bioassay. These results emphasize the cryptic role of endophytic fungi as a source of novel bioactive natural products and biocontrol agents. DOI 10.1099/mic.0.030916-0

The induction of defense responses in Pinus sylvestris L. seedlings by methyl jasmonate (MeJA) was investigated in three experiments. Two different MeJA application methods were tested, and induction of defense responses was assayed by seedling inoculation with Heterobasidion annosum (Fr.) Bref. and Lophodermium seditiosum Minter, Staley and Millar. In the first experiment, five-year-old P. sylvestris ramets of one clone were directly treated with MeJA, followed by inoculation with H. annosum. In the second experiment, open-pollinated Scots pine seedlings were treated with MeJA by direct spraying and vaporization, and inoculation with H. annosum was done using a slightly modified protocol. In the third experiment, open-pollinated Scots pine seedlings were treated with MeJA by vaporization and inoculated with L. seditiosum. Direct application of MeJA induced seedling mortality, and in some cases, decreased resistance to inoculation with H. annosum. Application of MeJA by vaporization was less stressful for seedlings, and resulted in increased resistance to both H. annosum and L. seditiosum. In addition, an unforeseen Neodiprion sertifer (Geoffroy) and Hylobius abietis L. infestation provided anecdotal evidence of the efficacy of MeJA in inducing resistance to insect pests as well. Further studies are required on the induction of resistance to additional diseases and pests. Induced resistance could be used as a possible protective mechanism for Scots pine seedlings prior to planting during reforestation of stands to increase vitality and survival. [ABSTRACT FROM AUTHOR]

Botryosphaeriaceae-related diseases occur worldwide in a wide variety of plant hosts. The number of studies targeting the distribution, diversity, ecology, and pathogenicity of Botryosphaeriaceae species are consistently increasing. However, with the lack of consistency in species delimitation, the name of hosts, and the locations of studies, it is almost impossible to quantify the presence of these species worldwide, or the number of different host–fungus interactions that occur. In this review, we collected and organized Botryosphaeriaceae occurrences in a single cured dataset, allowing us to obtain for the first time a complete perspective on species' global diversity, dispersion, host association, ecological niches, pathogenicity, communication efficiency of new occurrences, and new host–fungus associations. This dataset is freely available through an interactive and online application. The current release (version 1.0) contains 14,405 cured isolates and 2989 literature references of 12,121 different host–fungus interactions with 1692 different plant species from 149 countries. [ABSTRACT FROM AUTHOR]

In autumn 2018, during a study on the pathogens involved in the etiology of chestnut nut rot symptoms observed in three of the main sweet chestnut (Castanea sativa) growing areas in Sardinia (Site 1: 39°56'55"N/09°11'45"E; site 2: 39°58'20"N/09°09'41"E; site 3: 40°52'50"N/09°08'45"E), Gnomoniopsis smithogilvyi was found to be the main causal agent. In addition to G. smithogilvyi, 15 out of 450 nuts processed, yielded on potato dextrose agar (PDA, 39 g/L) at 22°C white colonies with dense aerial mycelium becoming dark grey after 4 to 7 days. Pycnidia were produced within 4 weeks in half-strength PDA incubated at room temperature under natural daylight. The hyaline, ellipsoid to fusiform and aseptate conidia measured 13.4-19.2 × 4.8-7.7 μm (n = 50). All morphological characters matched those reported for Neofusicoccum parvum by Phillips et al. (2013). Identity of isolates was confirmed by DNA sequence analysis of the internal transcribed spacer region (ITS) and part of the translation elongation factor 1-alpha gene (tef1-α). DNA extraction, PCR amplification reactions and DNA sequencing were carried out according to Linaldeddu et al. (2016). In the phylogenetic analysis based on combined ITS and tef1-α gene sequences the N. parvum isolates clustered within two well-supported subclades. In the first subclade (ML bootstrap = 88%) three isolates clustered together with the ex-type culture of N. parvum (CMW9081) while in the second subclade (ML bootstrap = 95%) three isolates clustered together with the ex-type culture of Neofusicoccum algeriense (CBS 137504), a species recently synonymised with N. parvum by Lopes et al. (2016). Sequences of six representative isolates were deposited in GenBank (MK968559-MK968564 and MT010339-MT010344 for ITS and tef1-α, respectively). The pathogenicity of six isolates, belonging to the two haplotypes, was undertaken by inoculating five asymptomatic nuts per isolate. After disinfecting the nut surface with 70% ethanol and removing a piece of shell (5 mm diameter) with a sterile cork borer, the nuts were inoculated with a same-sized agar-mycelium plug cut from the margin of a 5-day-old PDA colony. Ten control nuts were inoculated with a sterile PDA plug applied as described above. Inoculated nuts were kept in thermostat at 22 °C in the dark for 18 days. All nuts inoculated with N. parvum showed light-brown to dark necrosis of kernel associated with loss of tissue consistency. The symptoms were congruent with those observed in nature. All N. parvum isolates were successfully reisolated from all the inoculated nuts, fulfilling Koch's postulates. No lesions were observed on controls. N. parvum is recognized as an emerging plant pathogen worldwide. In particular, several studies report N. parvum as a growing threat to agricultural and forest ecosystems in the Mediterranean area (Larignon et al., 2015; Manca et al., 2020). This is the first report of N. parvum causing chestnut nut rot in Italy.

In this study a new 20-nor-ent-pimarane, named diplopimarane, was isolated together with sphaeropsidins A (9) and C (10), and (+)-epiepoformin (11) from organic crude extracts of Diplodia quercivora, a recently described oak pathogen originally found on declining Quercus canariensis trees in Tunisia. Diplopimarane was characterized as (1S,2R)-2,8,8-trimethyl-2-vinyl-1,2,3,4,5,6,7,8-octahydrophenanthrene-1,9,10-triol by spectroscopic, X-ray, optical, and chemical methods. It exhibited a wide range of activities including remarkable phytotoxicity on nonhost plants such as tomato cuttings, moderate antifungal activity against important plant pathogens, and moderate zootoxicity against Artemia salina. Its derivatives (2-4 and 6) were also tested for their phytotoxic and zootoxic activities. All these derivatives proved to be active against A. salina at 200 μg/mL, while 2 and 6 were also active on tomato cuttings. The other secondary metabolites (9, 10, and 11) herein reported for D. quercivora exhibited phytotoxic, antifungal, and zootoxic activity. This is the first report on the secondary metabolites secreted in vitro by this oak pathogen that could be key components of its adaptative strategies.