Soil-borne species of Phytophthora were isolated from 19 of 30 examined oak forest areas in Italy. The frequency of isolated Phytophthora spp. (35.2%) was signi®cantly correlated with soil pH and longitude of the sites. Eleven Phytophthora species were detected. Phytophthora cambivora, P. cinnamomi and P. cactorum were recovered from sites in central and southern Italy whereas P. quercina was isolated in the northern and central part of the country. Phytophthora citricola occurred all over Italy. Phytophthora quercina was the only species signi®cantly associated with declining oak trees.

Fungal endophytes that colonize forest trees are widespread, but they are less well known than endophytes infecting grasses. The few studies on endophytes in trees mainly concern the tropical areas and the northernmost latitudes, while similar investigations in the Mediterranean region have so far been scarce and incidental. Endophytes are studied mostly in economically important forests suffering from diseases, such as oak forests. One common endophyte that has received some study on oak is the mitosporic Discula quercina. This paper, after first addressing some basic problems on tree endophytes, examines the ecology of D. quercina in Mediterranean oak stands. D. quercina is usually viewed as a symptomless colonizer of healthy Quercus cerris, infecting new leaves early in the growing season, in an unstable equilibrium between transient mutualism/neutralism and latent pathogenesis. It is postulated here that climatic factors can change the endophytic nature of D. quercina, turning it into a weak pathogen or an opportunistic invader of senescing and indeed healthy trees. It is argued more generally that stochastic events can cause the lifestyle of an endophyte to switch from beneficial/neutral to pathogenic, transforming the tree-endophyte interaction, an interaction that depends in part on the matching genomes of the tree and endophyte, and on the environmental context.

Cork oak (Quercus suber) forests are economically and culturally intertwined with the inhabitants of the Mediterranean basin and characterize its rural landscape. These forests cover over two million hectares in the western Mediterranean basin and sustain a rich biodiversity of endemisms as well as representing an important source of income derived from cork production. Currently cork oak forests are threatened by several factors including human-mediated disturbances such as poor or inappropriate management practices, adverse environmental conditions (irregular water regime with prolonged drought periods), and attacks of pathogens and pests. All these adverse factors can interact, causing a complex disease commonly known as “oak decline.” Despite the numerous investigations carried out so far, decline continues to be the main pathological problem of cork oak forests because of its complex etiology and the resulting difficulties in defining suitable control strategies. An overview of the literature indicates that several pathogenic fungi and oomycota can play a primary role in the etiology of this syndrome. Therefore, the aim of this review is to analyze the recent advances achieved regarding the bio-ecology of the endemic and emerging pathogens that threaten cork oak trees with particular emphasis on the species more directly involved in oak decline. Moreover, the effect of climate change on the host-pathogen interactions, a task fundamental for making useful decisions and managing cork oak forests properly, is considered.

The composition of the endophytic fungal assemblages in Quercus cerris, Q. pubescens and Q. robur, three oak species most susceptible to decline, was investigated in Fagarè (Padova), Ulignano (Pisa), and Radda in Chianti (Firenze). The endophytic assemblages were studied as a function of health status of the whole tree and of twigs and leaves. The effect of station altitude was tested on Q. cerris. Samples were gathered from healthy and declining trees. In April (bud opening time) 20 twigs and 10 leaves were collected from each tree. Fungi were isolated from twig segments and leaf portions. A total of 23 fungal genera with 27 different species were isolated, in addition to a few sterile mycelia. Eleven species were found to be common to all three oak species, while other species were found only on one oak species, suggesting host specificity. Among the fungal species isolated, some were known to be pathogenic (Apiognomonia quercina, Colpoma quercinum, Diplodia mutila, Phomopsis quercina). The colonization frequency (CF) of pathogenic species varied between 0.9% for A. quercina in Q. cerris and 60.2% for P. quercina in Q. robur. Analysis of variance showed a statistically significant difference among the oak species tested. The CF was higher in declining trees in comparison with healthy trees, and also in twigs vs. leaves. The CF was found to be higher for Q. cerris trees growing at sea level as compared with those situated at an elevation of 350-400 m. In stands where, on account of particular ecological conditions, pathogenic behaviour is displayed simultaneously by more than one endophytic fungal species, trees accentuate their decline.

Investigation of the extracts of a culture of Cladosporium tenuissimum, a known hyperparasite of several rust fungi, gave rise to the isolation of cladosporols B-E (2-5). Their structure and stereochemistry were elucidated on the basis of 1 H and 13 C NMR evidence and CD measures.Cladosporols 1-5 were active in inhibiting the urediniospore germination of the bean rust agent Uromyces appendiculatus.