Multilocus Genotyping of 'Candidatus Phytoplasma Solani' Associated with Grapevine Bois Noir in Iran

none5Simple Summary Understanding the epidemiological cycle of Bois noir (BN) associated with 'Candidatus Phytoplasma solani' is vital to managing the disease effectively. The genotyping of 'Ca. P. solani' strains, according to tuf, vmp1, and stamp genes, contributes to a better knowledge of the geographical distribution of BN. In this study, we provide information on the molecular variants of 'Ca. P. solani' in Iranian vineyards. We observed six known vmp1 variants and discovered two new ones, V24 and V27. This information is useful for future investigations to more accurately understand the epidemiological cycle(s) of BN in Iranian vineyards, contributing to the management of the disease. Grapevine Bois noir (BN) is associated with 'Candidatus Phytoplasma solani'. It has been recorded in vineyards throughout Europe as well as in different countries in Asia, where it now constitutes a threat to Iranian viticulture. BN is strictly dependent on 'Ca. P. solani' strains, wild host plants, and insect vectors. The molecular typing of 'Ca. P. solani', based on the nonribosomal gene tuf and the two hypervariable markers vmp1 and stamp, is valuable for the reconstruction and clarification of the pathways of BN spread. In this study, an RFLP analysis was performed on the vmp1 gene, and a single-nucleotide polymorphism analysis confirmed new vmp types in 'Ca. P. solani'. A stamp gene phylogenetic analysis allowed us to distinguish between the new genotype infections in the grapevines and the 'weeds' Convolvulus arvensis and Erigeron bonariensis in Iranian vineyards, highlighting the close genetic relatedness of the strains of 'Ca. P. solani' found in Iran and Azerbaijan. The most common genotype in the grapevines was tuf b/V24/stamp III, which was associated with C. arvensis. This information contributes toward the identification of further routes of introduction of 'Ca. P. solani' in Iran to sustain the control measures for the management of BN.Jamshidi, Elham; Murolo, Sergio; Ravari, Sareh Baghaee; Salehi, Mohammad; Romanazzi, GianfrancoJamshidi, Elham; Murolo, Sergio; Ravari, Sareh Baghaee; Salehi, Mohammad; Romanazzi, Gianfranc

First report of Leucostoma cinctum on sweet cherry and European plum in Italy

Leucostoma cinctum and L. persoonii are the two species involved in Leucostoma canker, a disease that causes dieback of twigs and branches, bark cankers, gummosis, and tree decline of stone fruit. The aim of this study was to identify the causal agent of Leucostoma canker in Italian stone fruit orchards. More than 200 isolates of Leucostoma spp. were obtained from branches and twigs of sweet and sour cherry, apricot, and European plum trees that showed typical symptoms of Leucostoma canker. These trees were in commercial orchards of two Italian regions, Marche and Apulia, in central-eastern and south-eastern Italy, respectively. Soon after isolation, all of the colonies that grew on potato dextrose agar were white in colour, and after about 10 d they became olive-green. Growth was not observed at 33°C, and the pycnidia were larger than 1 mm diam. This information led to the identification of L. cinctum as the causal agent of these Leucostoma cankers. To our knowledge, this is the first report of L. cinctum on sweet cherry and European plum in Italy

New symptoms in Castanea sativa stands in Italy: chestnut mosaic virus and nutrient deficiency

The European chestnut characterizes both the landscape and economy of mountainous Italian areas. In recent years, new canopy disorders have been reported: “chestnut yellows”, often ascribed to phytoplasma and/or nutrient deficiency, and “chestnut mosaic”, associated with a virus (ChMV). Therefore, research was carried out in four Italian regions to describe the two symptomatic frames and assess their etiology. Surveys were conducted on 101 chestnut trees (23 with mosaic, 38 with yellowing, and 40 without symptoms). The phytosanitary status was monitored, and the new canopy disorders were detected, distinguishing between yellowing and mosaic. Moreover, leaf samples were collected for molecular and nutrient analyses. No phytoplasma infection was recorded, while ChMV was detected in 91.3% of samples with mosaic symptoms, 31.6% of yellowing samples, and 30.0% of asymptomatic samples. Yellowing was associated with Mn deficiency. On the other hand, ChMV-infected and healthy leaves had similar mineral contents, showing that mosaic symptoms are induced by the virus. Both disorders negatively affected photosynthesis efficiency. These phytosanitary problems are present in Italian chestnut woods and cause local effects, and a relationship with other biotic and abiotic factors can be hypothesized. Considering the increase in new records, these symptoms represent an emerging issue whose impact and spread need to be further monitore

Morphological and Molecular Identification of Seedborne Fungi in Squash (Cucurbita maxima, Cucurbita moschata).

Squash is one of the most important crops of tropical and temperate regions, and it can be affected by several fungal pathogens. Most of these pathogens infect the seeds, which become an efficient vehicle to disperse seedborne pathogens over long distances, with consequent severe crop losses. The main objective of this study was the identification of the principal seedborne fungi in seeds extracted from 66 samples of asymptomatic and symptomatic squash fruit (Cucurbita maxima, Cucurbita moschata) collected in two countries, Tunisia and Italy. The symptoms of fruit decay were identified and classified according to lesion size. Following the blotter test, 14 fungal species were detected from the seeds. Seedborne fungi were identified in all fruit samples tested, including asymptomatic fruit. The most frequent fungi from Tunisian seeds were Alternaria alternata (25.1%), followed by Stagonosporopsis cucurbitacearum (24.6%), Fusarium solani (16.6%), Rhizopus stolonifer (13.3%), F. fujikuroi (7.8%), Albifimbria verrucaria (3.3%), and Stemphylium vesicarium (2.3%). For the fruits from Italy, the most frequently identified fungal species in seed samples were Alternaria alternata (40.0%), followed by F. fujikuroi (20.8%), Stemphylium vesicarium (3.0%), and Curvularia spicifera (2.1%). Morphological identification was confirmed by molecular diagnosis using the available species-specific primers. Furthermore, specific primers were designed to identify Albifimbria verrucaria, Paramyrothecium roridum, and Stemphylium vesicarium. Application of seed-health testing methods, including such conventional and molecular diagnostic tools, will help to improve seed quality and crop yields

Status of Charcoal Canker on Oak Trees at a Site of Community Importance: Case Study of the Relict Castelfidardo Forest (SIC Area IT520008, Castelfidardo, AN, Italy)

Oaks are dominant and key tree species in Mediterranean forest ecosystems. However, in recent decades, oak forests have been heavily impacted by oak decline, a worldwide phenomenon exacerbated by climate change. The charcoal disease agent Biscogniauxia mediterranea is involved in the decline of Mediterranean oak formations in a variety of contexts. Here, we investigated the impact and role of B. mediterranea in the decline of oaks in Castelfidardo Forest, a relict wood of the late Holocene and a Site of Community Importance. We established five plots within which we recorded tree positions, any symptoms and signs of decline, association of B. mediterranea to declining trees, and deadwood and associated mycota. Of 471 oaks inspected, 7.0% showed brownish exudates on the stems, 46.9% showed epicormic shoots along the main trunk, and 24.4% showed black carbonaceous stromata on diseased branches and trunks. The decline was most severe for Quercus cerris, which comprised plots #4 and #5, at 50.0% (81/162 trees) and 29.0% (33/114), respectively; then for Quercus robur for plot #3, at 40.0% (38/95); and finally for Quercus pubescens for plots #1 and #2, at 13.7% (7/51) and 12.3% (6/49), respectively. Bark tissues were collected from trees with charcoal cankers and taken to the laboratory for microscopic examination and identification by mycological and molecular methods. This investigation revealed a close association between oaks with pronounced reduction of vitality and incidence of B. mediterranea. Deadwood was equally distributed among the five plots, and was heavily colonized by Basidiomycota. The high incidence of the charcoal canker pathogen B. mediterranea appeared to be related to environmental stresses. However, the absence of silvicultural management, high competition among physiologically mature trees, and the geographic isolation of this residual forest may have predisposed oaks to decline

Endophytic Fungi as Potential Biological Control Agents against Grapevine Trunk Diseases in Alentejo Region

Grapevine trunk diseases (GTDs) are the most widespread fungal diseases, affecting grapevines in all the major growing regions of the world, and their complete eradication is still not possible. Aiming to search alternatives to avoid the spread and high incidence of these diseases, the present work intended to molecularly identify the grapevine endophytic community, the phytopathogenic fungi associated with GTDs in vineyards within the Alentejo region, and to test potential antagonist microorganisms as biological control candidates against GTDs-associated fungi. Grapevine endophytic community showed a wide variety of fungi in GTDs’ asymptomatic and symptomatic plants, nine of them previously described as GTDs-associated fungi. GTDs prevalent fungi identified in symptomatic plants were Diaporthe sp., Neofusicoccum sp., and H. viticola. Almost all these fungi were also detected in asymptomatic plants, which shows the importance of investigating the interactions of fungal communities and confirms the need for early diagnosis of these diseases. Direct inhibition antagonism tests were performed among identified endophytes and GTDs phytopathogenic fungi, and all the endophyte fungi showed potential as biocontrol agents. Our findings suggest that endophytes are promising candidates for their use in biological control due to their antagonistic activity against the mycelia growth of some GTDs-associated fungi

Colonization of Vitis spp. wood by sGFP-transformed Phaemoniella clamydospora, a tracheomycotic fungus involved in esca disease

none3Una foto dell'articolo è riportata sulla copertina del fascicoloLandi L.; Murolo S.; Romanazzi G.Landi, Lucia; Murolo, Sergio; Romanazzi, Gianfranc

Effects of grapevine cultivar, rootstock and clone on esca disease

Esca is one of the main causes of reduction of production, plant decline and death in vineyards of most viticultural areas of the World. We determined the foliar esca symptoms on a range of grapevine cultivars in three centraleastern Italian vineyards during summer 2008, characterized by conducive conditions for the disease. In vineyard AP1, the incidence of symptomatic plants was recorded for 67 Vitis vinifera cultivars. Among white-berried cultivars, Passerina, Sauvignon blanc, Manzoni bianco, and Riesling, had highest incidence of symptomatic plants (28–35 %), while cvs. Chiapparù, Grechetto, Perdea, Verdicchio, Fiano and Pinot blanc had lowest (0–5 %). Among red-berried cultivars, Rebo had highest incidence of symptomatic plants (>35 %), with lowest for cvs. Lacrima, Brugentile, Sirah, and Limberger (0 %), followed by Gallioppo, Merlot, and Nebbiolo (<5 %). However, mean values of symptomatic plants among red and white cultivars were similar. The six cultivars monitored in vineyard AP2 confirmed this cultivar susceptibility ranking. Furthermore, in vineyard AN1, incidence of esca symptoms on seven cultivars grafted onto different rootstock was recorded. Cvs. Fiano and Sauvignon grafted onto SO4 showed higher disease incidence than combinations with 1103P. This result can be ascribed to the higher drought resistance of 1103P as compared to SO4, supporting the hypothesis that esca symptoms occur mostly in stressed plants. Significant differences in the symptom expression were recorded just among clones of Sauvignon, while they were not found in Chardonnay, Riesling and Pinot blanc. Our data give useful information for growers in planning cultivar/rootstock combination choice for new vineyards, and can provide an idea of possible evolution of esca along time in an already established vineyard