Colletotrichum clavatum sp. nov. identified as the causal agent of olive anthracnose in Italy

Molecular analyses of a large population of isolates, previously identified as group B or genetic group A4 of the Colletotrichum acutatum species complex, mainly of Italian origin from olive, but also from other hosts collected since 1992, confirmed a well-resolved phylogenetic lineage with distinctive phenotypic characters which can be recognized as a separate species. Based on RAPD genomic fingerprinting, ITS and β-tubulin DNA sequences, this species was clearly distinct from C. acutatum sensu stricto, C. fioriniae and C. simmondsii as well as from the genetic groups A1, A6, A7 and A8, all previously referred to as C. acutatum sensu lato. Group A4 is widespread in Europe, being responsible for olive anthracnose epidemics in some Mediterranean countries, including Greece, Italy, Montenegro, Portugal and Spain; moreover, it causes anthracnose diseases on a wide range of other hosts including about 20 different genera of woody and herbaceous plants, ornamentals and fruit trees. This new anamorphic taxon is described as Colletotrichum clavatum sp. nov

phytophthora cinnamomi involved in the decline of holm oak quercus ilex stands in southern italy

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Polyketide synthases of Diaporthe helianthi and involvement of DhPKS1 in virulence on sunflower

Background The early phases of Diaporthe helianthi pathogenesis on sunflower are characterized by the production of phytotoxins that may play a role in host colonisation. In previous studies, phytotoxins of a polyketidic nature were isolated and purified from culture filtrates of virulent strains of D. helianthi isolated from sunflower. A highly aggressive isolate (7/96) from France contained a gene fragment of a putative nonaketide synthase (lovB) which was conserved in a virulent D. helianthi population. Results In order to investigate the role of polyketide synthases in D. helianthi 7/96, a draft genome of this isolate was examined. We were able to find and phylogenetically analyse 40 genes putatively coding for polyketide synthases (PKSs). Analysis of their domains revealed that most PKS genes of D. helianthi are reducing PKSs, whereas only eight lacked reducing domains. Most of the identified PKSs have orthologs shown to be virulence factors or genetic determinants for toxin production in other pathogenic fungi. One of the genes (DhPKS1) corresponded to the previously cloned D. helianthi lovB gene fragment and clustered with a nonribosomal peptide synthetase (NRPS) -PKS hybrid/lovastatin nonaketide like A. nidulans LovB. We used DhPKS1 as a case study and carried out its disruption through Agrobacterium-mediated transformation in the isolate 7/96. D. helianthi DhPKS1 deleted mutants were less virulent to sunflower compared to the wild type, indicating a role for this gene in the pathogenesis of the fungus. Conclusion The PKS sequences analysed and reported here constitute a new genomic resource that will be useful for further research on the biology, ecology and evolution of D. helianthi and generally of fungal plant pathogens

Phytophthora × pelgrandis Causes Root and Collar Rot of Lavandula stoechas in Italy.

In 2007, Phytophthora isolates with atypical morphological and biological characteristics were found associated with root and collar rot of potted plants of Stoechas lavender (Lavandula stoechas) in an ornamental nursery in Italy. A polyphasic approach, including morphological and cultural observations, sequencing the ITS-rDNA region, the Pheca and the mitochondrial coxI genes, multiplex PCRs with primers specific for P. nicotianae or P. cactorum, as well as random amplified polymorphic DNA–polymerase chain reaction, was used to characterize these isolates. On the basis of morpho-cultural and molecular analyses, the isolates from Stoechas lavender were identified as Phytophthora × pelgrandis, a natural hybrid of P. nicotianae × P. cactorum previously reported in other European countries, the Americas, and Taiwan, as a pathogen of ornamentals and loquat plants. In pathogenicity tests using potted plants of Stoechas lavender, the P. × pelgrandis isolates, similarly to the parental species P. nicotianae, induced the symptoms observed on plants with natural infections and were reisolated only from artificially inoculated plants. Dispersal of P. × pelgrandis on this host could exacerbate the damage caused by Phytophthora root and collar rot, of which the main causal agent presently is P. nicotianae on lavender in Europe. Application of hygienic measures is important to reduce the proliferation and spread of the Phytophthora hybrids

Mal secco disease caused by <i>Phoma tracheiphila</i>: a potential threat to lemon production worldwide

Lemon (Citrus limon (L.) Burm. f) is the most popular acid citrus fruit because of its appealing color, odor, and flavor. World production of lemons was about 7 to 8 million metric tons in 2007. Major producers and exporters of lemon in the world include Argentina, Spain, Iran, the United States, Italy, Turkey, Egypt, Greece, South Africa, Cyprus, Morocco, and Israel (www.cga.co.za). Argentina and Italy are major suppliers of lemon juice, and Spain, Argentina, Turkey, the United States, South Africa, Italy, Chile, Egypt, Uruguay, India, Jordan, Cyprus, China, and Iran are the leading exporting countries of fresh fruit. Mal secco of citrus is a highly destructive vascular disease of lemon, presently confined to the Mediterranean basin, which has a relevant economic impact on the lemon industry in this geographic region. Mal secco is caused by the mitosporic fungus Phoma tracheiphila (Petri) Kantschaveli &amp; Gikachvili (syn. Deuterophoma tracheiphila Petri). The name of the disease stems from the Italian words male (disease) and secco (dry). The term “malsecco,” referring to nonspecific symptoms, was initially used in a broad sense to indicate citrus diseases of various origins. Later, Petri used the term “mal secco of citrus” in a more strict sense to indicate the tracheomycotic disease that was spreading in lemon orchards in Sicily. Mal secco first appeared affecting lemon trees on the islands of Chios and Poros (Greece) near the end of the nineteenth century. In 1929, Petri described the fungus causing mal secco as a new species and named it Deuterophoma tracheiphila, which he proposed as the type-species of the new genus DeuterophomaPetri. The species was transferred to Phoma by Kantschaveli and Gikachvili in 1948. Later, Ciccarone and Russo and Ciccarone, who amended the description of the fungus, confirmed this binomial as the correct name