Phytophthora is one of the most destructive genera of plant pathogens, comprising more than 260 described species, with numerous cryptic and undescribed taxa that remain undetected. These oomycetes cause severe diseases in agriculture, horticulture, forestry and natural ecosystems resulting in major economic losses, altered forest dynamics and biodiversity decline. The Mediterranean Basin is particularly vulnerable to these pathogens, due to high crop diversity, rich endemic flora, intensive plant trade networks, and climatic conditions that favour pathogen establishment and spread. Most damaging Phytophthora species are exotic, introduced primarily through infected nursery stock, contaminated soil or irrigation and river water. Their impacts are also affected by environmental stresses, climate change, intensive cultivation and interactions and connectivity among agricultural, forest and natural landscapes. New diagnostic tools and global surveys have revealed significant and previously undiscovered diversity and ongoing biosecurity risks for these pathogens. Effective management and mitigation require harmonised surveillance systems, robust early detection tools, production of pathogen-free planting material, improved hygiene and cultivation practices, and breeding for host tolerance. These approaches must be integrated within broad landscape-level strategies, to safeguard biodiversity and enhance ecosystem resilience across the Mediterranean Basin ecosystems.
Oak decline, in acute and chronic forms, is an emerging challenge in the forest and urban environments of Europe and the Mediterranean basin. Oak trees have central ecological and cultural roles: they support diverse organism communities, are involved in hydrological and biogeochemical cycles, and provide ecosystem services in natural and anthropised landscapes. Populations of Quercus species are increasingly threatened by combined effects of extreme weather events, soil degradation, hydrological imbalance, and increasing numbers of emerging pathogens. These factors interact in complex ways, often accelerating decline processes and complicating diagnoses and management. Advances in visual assessment, remote sensing, and molecular tools are improving early decline diagnoses, and accurate assessments of severity. Integrated management approaches, incorporating vegetation management, adaptive silviculture, and soil and water conservation, offer promising pathways to improve oak tree resilience. Attention is required in urban settings, where chronic abiotic stress and site constraints amplify tree vulnerability. Long-term monitoring networks and multidisciplinary approaches are essential for understanding disease progression, anticipating risks, and guiding effective interventions. This review synthesises current knowledge on oak decline dynamics, diagnostic approaches and management strategies, providing a framework to support sustainable, science-based strategies, to mitigate the disease and ensure long-term viability of oak-dominated landscapes.
Grapevine cultivation in Montenegro has long historical and economic significance, with wine being a key trade product. However, under Montenegrin agroecological conditions, grapevine cultivation is increasingly threatened by plant diseases, particularly the Esca disease complex (EDC) which is the most economically damaging among grapevine trunk disease. A 4 year survey from 2021 to 2024 confirmed presence of EDC in all Montenegrin winegrowing regions, as Grapevine Leaf Stripe Disease (GLSD) and apoplexy. Symptom severity varied by grapevine variety and vineyard age, with the greatest incidence in vineyards aged 30–35 years. The indigenous varieties Vranac and Kratošija were more susceptible than introduced varieties (Syrah, Merlot, Chardonnay, Cabernet Sauvignon). Laboratory analyses of symptomatic trunks yielded numerous isolates of endophytic microorganisms. Preliminary identification of these, based on morphology, and molecular PCR diagnostics targeting the ITS rRNA genomic region, plus analyses of the partial tub2 and tef1-α genes, identified three key fungi responsible for EDC in Montenegro: Phaeoacremonium minimum, Phaeomoniella chlamydospora, and Fomitiporia mediterranea. In the investigated vineyards, numbers of empty places remaining after removal of dead grapevines varied, depending on vineyard age and grape variety. In a 21-year-old vineyard where dead vines were not replaced, vine loss of 32%, and direct yield reduction of 44%, were recorded, highlighting the substantial economic impact of esca disease.
In late 2022, uncharacteristically small fruits of Washington Navel sweet orange (Citrus sinensis L. ‘Washington Navel’) with fruit creasing symptoms were sampled in a small orchard on the coast of Croatia. The virome in the fruits was investigated using metagenomic analysis, which showed presence of citrus dwarfing viroid (CDVd) and citrus leaf blotch virus (CLBV). The record of CLBV is the first for Croatia. Nucleotide sequence analysis of the RdRp region indicated that the Croatian CLBV isolate shared closest sequence similarity to two isolates from kumquat Nagami from Sicily. Full-genome phylogeny of CLBV accessions indicate that isolates from citrus cluster together and are mostly distinct from isolates from non-citrus hosts. The use of Fast Technology for Analysis (FTA) cards was evaluated, as an alternate for CLBV sampling, and as a transport-safe method for obtaining viral RNA templates for RT-PCR. FTA cards in combination with an extraction-free protocol were shown to be usable when columella tissue was used to imprint, but leaf prints were unreliable.
The plant pathogenic bacterium Pseudomonas avellanae, the causal agent of decline and dieback of hazelnut (Corylus avellana), affects vascular tissues of host trees and leads to the rapid wilting of leaves. Severe damage to hazelnut orchards has been reported in northern Greece and central Italy. In 2024, hazelnut trees (cv. Tonda di Giffoni) showed symptoms of rapid leaf wilting and brown discolouration of vascular tissues in the branches. Isolations resulted in convex, levan-positive, mucoid, cream-whitish bacterial colonies on Nutrient agar (plus 5% sucrose), which LOPAT results (+---+) identified the bacteria as Pseudomonas syringae group Ia. Preliminary identification of isolates was achieved using specific conventional PCR (cPCR) for P. avellanae. Further genetic identification and characterization was carried out using multilocus sequence analysis (MLSA) using five housekeeping genes (gyrB-gapA-gltA-rpoD-recG). Repetitive ERIC-PCR fingerprinting of two Serbian isolates from hazelnut, 13 Italian, and one Greek isolate of P. avellanae revealed three distinct molecular patterns. The Serbian isolates clustered with the Italian strains, while the Greek strain formed a more distinct group. Pathogenicity assessments, carried out by inoculating 1-year-old hazelnut plants (Tonda di Giffoni), resulted in the development of necrosis at the inoculation sites 10 d post-inoculation, which reached lengths 15-20 cm longitudinally along the stems within 2 months. The inoculated bacterium was re-isolated from the stems of inoculated plants. This study highlights the emerging threat of P. avellanae to hazelnut production, with significant implications for the European hazelnut industry. Spread of this pathogen across regions, and the potential impacts on orchard health, emphasize the need for enhanced monitoring and disease management strategies.
Rhizoctonia root rot (RRR) reduces soybean yields, and is influenced by soil conditions, but there is a lack of knowledge on effects of soil moisture and soil type on disease severity, in subtropical environments. Increased RRR during periods of water deficit in southern Brazil reinforces requirement to understand interactions between soils and moisture affect severity of the disease and crop yields. Two greenhouse experiments were conducted to evaluate combined effects of soil moisture (50, 65, 80, or 95% water holding capacity; WHC) and soil type (Acrisol, Cambisols, Leptosol, or Nitisol) on soybean RRR severity and yield components. Increasing soil moisture from 50 to 95% WHC linearly reduced RRR severity and linearly increased numbers of soybean pods, grains, and grain weights, inside and outside RRR patches. In Experiment 1, at 65% WHC, RRR severity was less in Leptosol than on Acrisol, but there were no differences between these two soils and the other soil types. In Experiment 2, soil type did not affect RRR severity evaluated at all the tested soil moistures. High soil moisture (≥ 80% WHC) mitigated RRR, and extended the soybean growth cycle. Low soil moisture (50–65% WHC) intensified RRR severity, increased plant death, and reduced soybean grain yields.
rus production is economically important in the Chlef Valley, Algeria, but faces several challenges from diseases that threaten yields, fruit quality, and long-term sustainability of orchards. During recent decades, several citrus orchards have shown decline and severe symptoms, mostly associated with tristeza and caused by the virulent VT strain reported in 2019. To update current distribution and strains of tristeza pathogens and potential aphid vectors, an additional survey was conducted in the Chlef Valley from 2021 to 2024. Samples collected from different citrus areas were serologically assessed, showing an increase in the infection rates from 3.2% in 2019 to 4.24% in 2024. The molecular genotype characterization using strain specific RT-PCRs confirmed the presence of the pre-existing T30 and VT genotypes, and two new strains, S1 and T3, were also detected. This study has confirmed the widespread dissemination of the virulent VT genotype of CTV, and has detected additional CTV strains. Discovery of new strains and the further spread of the severe VT genotype, combined with detection of the aphid vector Aphis gossypii Glover, poses significant threats to the citrus industry in Algeria. This situation requires proactive measures by the National Phytosanitary Services, including extending surveillance to other citrus Algerian production regions.
Botryosphaeriaceae pathogens have broad host ranges and can move between hosts, particularly those with overlapping geographic distributions. Cross-infection potential and virulence were assessed for 40 isolates of Botryosphaeria, Diplodia, and Neofusicoccum (11 species), originally isolated from apple, olive, or grapevine crops. Progression of asymptomatic colonization beyond visible necrotic lesions was also assessed, to determine minimum pruning distances required for effective pathogen removal. The assays were conducted using detached lignified stems of apple and olive, and dormant cuttings of grapevine. All the isolates cross-infected and colonized stems or cuttings of the three potential hosts, confirming host-independence of these pathogens. Most of the Neofusicoccum isolates consistently caused the largest lesions across the three inoculated hosts. Asymptomatic colonization was not detected at distances of 20 or 30 cm beyond visible lesions. However, at 10 cm, one isolate of N. parvum colonized the three hosts, and one isolate of D. seriata colonized olive host. These results highlight the challenges for managing these pathogens in fruit crops growing in close proximity, and emphasize the urgency of revising the minimum pruning distances required for successful pathogen removal.
. The stone fruit industry, particularly plum (Prunus domestica) production, is important to the Albanian economy. The Prunus domestica `Tropojane' predominates due to its high and stable productivity, adaptability, and superior organoleptic qualities. Assessing phytosanitary status of this fruit plant is important, to ensure sustainable production and preserve genetic resources. During the spring seasons of 2022, 2023 and 2024, 129 samples of `Tropojane' plum were collected across the regions of Tropoja, Kukes, Has, Puka, Durres, Paskuqan, and Kamez of Albania. All samples were tested by ELISA, PCR, and qPCR to detect plum pox virus (PPV), the most destructive virus infecting plum, and to screen for additional stone fruit viruses including Prunus necrotic ringspot virus (PNRSV ), prune dwarf virus (PDV ), apple mosaic virus (ApMV ), and apple chlorotic leafspot virus (ACLSV ). ELISA tests demonstrated that PPV was present in 35.5% of the samples, whereas RT-PCR and RT-qPCR assays detected PPV in 45.6% of the samples, confirming greater sensitivity of the PCR assays for virus detection. No infections with other assessed stone fruit viruses were detected. PPV identity was confirmed by sequencing, and phylogenetic analyses showed that the Albanian isolates clustered within the Rec strain group, also indicating their possible regional origin. Meristem culture was employed as a sanitation strategy for PPV-infected explants. Differences in regeneration capacity among plum populations were observed, yet stable in vitro cultures were established in all cases, and molecular diagnostics confirmed that regenerated plantlets were PPV-free. In vitro shoots were successfully subcultured, rooted, and acclimatized. These results highlight the need to
This study evaluated the potential of Trichoderma asperellum ICC012 and T. gamsii ICC080 to protect almond pruning wounds from infections caused by three major almond trunk pathogens: Diplodia seriata, Eutypa lata, and Neofusicoccum parvum. Dual-culture antagonism assays and two in planta wound protection trials were conducted to assess their efficacy. In the first trial, treatments with T. asperellum ICC012 + T. gamsii ICC080 were applied one or seven days before or after pathogen inoculation to test the impact of application timing, while the second trial focused on preventive strategies, comparing single versus double applications prior to inoculation. Both Trichoderma strains alone and mixed were able to inhibit pathogen growth in vitro. Experiments in planta showed that only pre-infection applications significantly protected pruning wounds, though their efficacy differed by pathogen and treatment strategy. Protection was highest against E. lata and D. seriata, in which a single treatment prevented infection, whereas N. parvum proved more challenging; only a double pre-inoculation application markedly improved its control. Our results demonstrate that preventive wound protection by T. asperellum ICC012 + T. gamsii ICC080 is essential for effective control. Incorporating these biocontrol agents into almond orchard management can substantially reduce trunk disease infections and limit reliance on synthetic fungicides in Mediterranean production systems.
. This study aimed to identify the species of Cylindrocarpon-like anamorphs associated with black root rot of strawberry seedlings and field-grown plants in Aydin province, Turkiye. Samples of strawberry seedlings before planting and diseased plants after planting were collected from 41 strawberry fields during two production seasons (2009-2010 and 2010-2011) in Sultanhisar of Aydin. Incidence of pathogenic Cylindrocarpon spp. in seedlings was 0.11-0.54%, and fungal pathogens were isolated from 15.8% of diseased plants in 2009/2010 and were-4.6% in 2010/2011. Seven Cylindrocarpon-like pathogenic isolates recovered from seedling roots and 17 from diseased plants were further identified as Dactylonectria novozelandica (DN; 12 isolates), Dactylonectria torresensis (DT; nine), Dactylonectria macrodidyma (DM; one), and Ilyonectria europaea (IE; two isolates), using multilocus sequence analysis (MLSA) with sequencing of tef1, tub2, and his3 partial genes. Cultural and morphological characteristics were determined for representative isolates of four species. Pathogenicity tests indicated that the most aggressive species could cause necrosis on detached strawberry stolons, and severity of plant decline in pots experiments was greatest from DT, less from DN and IE, and least from DM. This is the first report of D. novozelandica, D. torresensis, D. macrodidyma in Turkiye, and I. europaea in the world, as causes of black root rot in strawberry.
. Anthracnose, caused by Colletotrichum species, is a major disease of avocado (Per sea americana) that significantly reduces fruit quality and export potential in Chile. Colletotrichum species associated with this disease were identified and their pathogenicity to avocado was assessed. In the summer of 2018, healthy fruits (n = 1,335) were sampled from three commercial groves located in the Metropolitan, O'Higgins and Valparaiso regions of Chile, and from a non-commercial grove and local markets. Fruits were stored until symptoms developed, indicating anthracnose incidence in commercial groves ranging from 10 to 50%. A total of 146 fungal isolates were obtained from symptomatic fruit and were initially identified as Colletotrichum spp. Fifty representative isolates were further identified through multilocus phylogenetic analyses. Ten species belonging to four species complexes were identified. Colletotrichum cf. cigarro was the most frequent taxon (n = 17), followed by C. pyricola (n = 9), C. gloeosporioides (n = 6), C. jiangxiense (n = 5), C. karsti (n = 4), C. anthrisci (n = 3), C. brassicicola (n = 3), C. laurosilvaticum (n = 1), C. fructicola (n = 1), and C. perseae (n = 1). Pathogenicity tests reproduced anthracnose symptoms in inoculated fruits, whereas control fruits remained symptomless, and revealed differences in virulence among isolates and species. This study provides the first report of C. brassicicola, C. laurosilvaticum and C. pyricola as causal agents of avocado anthracnose, highlights the diversity of Colletotrichum species in Chilean avocado groves, and provides insights for improved management strategies for avocado anthracnose.
Gnomoniopsis castaneae has become an important pathogen of European chestnut (Castanea sativa), affecting fruits and colonizing shoots and branches, as well as galls caused by the oriental chestnut gall wasp (Dryocosmus kuriphilus). On apparently asymptomatic fruits, G. castaneae can colonize the endosperms, causing quality issues, especially in post-harvest. Given the alarming spread of G. castaneae infections in Italy and the current knowledge gaps regarding aspects of G. castaneae biogeography and virulence, research was addressed to: 1) evaluate occurrence of G. castaneae in chestnut nuts and branches in different Italian regions; 2) study occurrence and distribution of the two known G. castaneae haplotypes throughout Italy; and 3) evaluate their virulence on chestnut under different water regimes. Fungal isolation from representative chestnut branch and nut samples consistently yielded colonies that were morphologically consistent with G. castaneae, the identity of which was confirmed by analysis of ITS sequences. Analysis of a-tubulin sequences confirmed the presence of two distinct genetic lineages (Gc-haplotypes A and B). To assess pathogenicity, G. castaneae isolates were inoculated onto chestnuts, chestnut cuttings and 3-year-old young plants grown under two water regimes. All assessed isolates were pathogenic on chestnut, and water-stressed plants exhibited more extensive necrosis than well-watered plants when inoculated with the Gchaplotype A, highlighting the influence of environmental conditions on disease expression. This study expands current knowledge on the distribution, genetic diversity, and effects of water stress on the pathogenic potential of G. castaneae on chestnut.
Grapevine leafroll-associated virus 4 (GLRaV-4, Ampelovirus tetravitis) has considerable genetic diversity. A survey was conducted in central, western, and southern Algeria to investigate the distribution and the genetic diversity of GLRaV-4 in commercial and autochthonous grape cultivars. DAS-ELISA detected an overall grapevine infection rate of 18.2%, and infections in a subset of samples were confirmed by RT-PCR. Analysis of the P23 protein gene sequence revealed six known phylogenetic groups, with Algerian isolates clustering in strains -4, -5, -6, -9, and -Pr of GLRaV-4. In addition to this virus, three viruses and two viroids were identified using high throughput sequencing: grapevine Pinot gris virus (GPGV, Trichovirus pinovitis), grapevine leafroll-associated virus 2 (GLRaV-2, Closterovirus vitis), grapevine fanleaf virus (GFLV, Nepovirus foliumflabelli), hop stunt viroid (HSVd, Hostuviroid impedihumuli) and grapevine yellow speckle viroid 1 (GYSVd-1, Apscaviroid alphaflavivitis). This study was the first research on genetic diversity of GLRaV-4 in Algeria.
Field surveys were conducted in the northeastern and northwestern regions of Tunisia between 2013/2014 and 2018/2019 growing seasons to identify viruses that infect faba bean and chickpea crops. Field observations showed that 18.8% of the faba bean and 21.0% of the chickpea fields surveyed had virus-like symptoms. These rates exceeded 20% during the growing seasons from 2013/2014 to 2018/2019, and were most common in the 2014/2015 growing season (28.6% of surveyed faba bean fields and 37.5% of chickpea fields showed virus-like symptoms in more than 20%). Totals of 1,538 faba bean and 1,511 chickpea plant samples showing yellowing and stunting symptoms were collected from 144 faba bean and 124 chickpea fields, . All collected samples were tested by tissue blot immunoassay (TBIA) using six monoclonal antibodies. These results showed that chickpea chlorotic stunt virus (CpCSV; Polerovirus CPCSV) was the most prevalent in faba bean and chickpea, with incidences of 20.2% and 37.6%, respectively, followed by beet western yellows virus (BWYV; Polerovirus BWYV) (13.5 and 9.7%), bean leafroll virus (BLRV; Luteovirus phaseoli) (3.7 and 3.3%), and faba bean necrotic yellows virus (FBNYV; Nanovirus necroflaviviciae) detected only in faba bean (6.6% of faba bean samples tested). In addition, TBIA results indicated that single virus infections were more prevalent than mixed infections in both crops. Mixed infections were predominantly co-infections involving viruses in Polerovirus (Solemoviridae), particularly CpCSV and BWYV (93% in faba bean and 69% in chickpea). Twenty-six samples that reacted positively with different monoclonal antibodies were assessed with reverse transcription-polymerase chain reaction (RT-PCR) using generic and specific primers followed by sequencing of the partial coat protein (CP) gene. The sequence analyses confirmed presence of CpCSV, BWYV, BLRV, brassica yellows virus (BrYV; Polerovirus TUYV), and turnip yellows virus (TuYV; Polerovirus TUYV). Comparative sequence analyses of the Tunisian isolates indicated that 13 CpCSV sequences had nucleotide sequence similarities of 95 to 99% with the reference isolate (EU541266) belonging to serotype I, and six BLRV isolates had similarities of 96 to 99% with BLRV reference isolate (PP333098). One sample (TuCp265-19) had a mixed infection with CpCSV and BLRV. Six isolates initially detected using BWYV-specific primers were sequenced and analyzed. BLASTn results showed that only three isolates were closely related (98 to 100%) to BWYV (OM419176), while the remaining four isolates were identified as Polerovirus TUYV and showed greatest similarity to BrYV (LC428361) and TuYV (OP699039), indicating co-occurrence of two distinct Polerovirus species within the analyzed samples. There is no information on the genetic variability of legume viruses in Tunisia, so this study shows that these viruses should be considered when developing disease management strategies to improve faba bean and chickpea production in Tunisia.
Knowledge of the ecology of biological control agents (BCAs), previously reported to be effective against the citrus vascular pathogen Plenodomus tracheiphilus, is required to improve scheduling of BCA field applications. Culture-dependent methods (dilution plate and direct plating) and culture-independent qPCR assays were used to determine survival of Bacillus amyloliquefaciens QST 713 and Trichoderma asperellum ICC 012 + T. gamsii ICC 080 on citrus stem and leaf tissues following foliar applications, and root endospheres and rhizospheres following root drenches with these Trichoderma BCAs. Viable population levels of B. amyloliquefaciens did not change over time on treated stems, whereas these decreased in leaf samples after 14 d. The qPCR assay detected B. amyloliquefaciens in all collected samples, with no temporal changes in population levels. Although the qPCR assay detected T. asperellum and T. gamsii in leaf and stem tissues, these fungi were isolated only from stem tissues, with increased isolations at 21 d post treatment compared with 7 d. Neither qPCR nor culturing detected Trichoderma species in citrus vascular root tissues. However, qPCR and culturing detected these fungi in host rhizospheres at 7, 14 and 21 d post inoculation, confirming their rhizosphere competence. This study has provided insights into colonization and survival within citrus plants of B. amyloliquefaciens and T. asperellum + T. gamsii contained in commercial biocontrol products. These indicate that integrating qPCR and culture-dependent approaches is important for detecting and quantifying these BCAs. The endophytic lifestyle of B. amyloliquefaciens and T. asperellum + T. gamsii makes them likely to provide long-term biological control. These results also indicate that the selected Bacillus and Trichoderma agents could spread and colonize citrus tissues over extended periods, and especially after host pruning or damage, which could promote plant colonization and protection from pathogens.
Pea seed-borne mosaic virus (PSbMV) can reach high levels of seed infection in Australian field peas, resulting in severe crop losses. Endemic, pea-derived PSbMV strains can cause lentil seed infection under experimental conditions, but PSbMV transmission has not been detected in grain harvested from lentil crops in Australia. In contrast, specialised PSbMV strains that are seed-borne in lentils occur in countries with long histories of lentil cultivation. A total of 29 PSbMV isolates were obtained from seeds of 11 exotic lentil accessions held at the Australian Grains Gene-bank, and the isolates were identified as the P2 pathotype using the standard set of pea differentials. However, testing with an additional set of lentil genotypes revealed two distinct pathotypes, tentatively designated P2a and P2b. Screening of lentil accessions previously reported to possess resistance to PSbMV or to bean yellow mosaic virus (BYMV), as well as Australian (25) and North American (3) cultivars, identified resistance to the P2b pathotype in several entries. In contrast, resistance to the more virulent P2a pathotype was only detected in three germplasm accessions that were previously reported to be BYMV resistant. Incursions of lentil seed-borne PSbMV strains pose major risks to the Australian lentil industry. Collaboration with research programmes in countries where lentil seed-borne PSbMV is present will facilitate resistance screening against a possible wider range of pathotypes, and support research on virulence genes and virus genes controlling seed transmission. As large-scale testing with exotic virus strains is difficult to implement in Australia, development of molecular markers for resistance to the most virulent PSbMV strains is desirable.
. The Castagno dei cento cavalli (One hundred horse chestnut) is a monumental Castanea sativa (sweet chestnut) located on the eastern slope of Mount Etna in Sicily (Italy), and is the oldest (>2000 years) known sweet chestnut in the world. In the spring of 2022, symptoms indicating virus infection were observed on this tree. Attempts to visualize virus particles from extracts using transmission electron microscopy were unsuccessful, so high-throughput RNA sequencing was carried out. This identified a tripartite genome (RNA1, RNA2, and RNA3) corresponding to apple mosaic virus (species Ilarvirus ApMV). Serological analyses using polyclonal antiserum confirmed infection in symptomatic but not in asymptomatic leaf samples. This is the first report of ApMV infecting C. sativa, and this virus possibly threatens monumental trees elsewhere internationally. Although efficient ApMV vectors are lacking, limiting the risk of spread, this knowledge highlights the need for monitoring monumental trees as potential reservoirs of novel host-virus associations, and the importance of careful management of this Sicilian botanical monument.
Magnolia grandiflora is an important ornamental tree in urban areas. In 2025, leaf spot symptoms were observed on M. grandiflora leaves in Viterbo, Italy. The causal agents were isolated and identified through morphological characterization and multilocus phylogenetic analysis of EF1-alpha, RPB1 and RPB2 gene sequences, and were identified as Fusarium venenatum and F. clavum. Pathogenicity tests on healthy M. grandiflora leaves produced characteristic brown leaf spots within 3 d post-inoculation. Re-isolations of the inoculated fungi confirmed Koch's postulates. This study demonstrated that F. venenatum and F. clavum caused the leaf spot symptoms on Magnolia, and is the first report of this disease in Italy. These results provide the basis for developing targeted disease management strategies for emerging diseases caused by these fungi in urban areas.
Citrus is an economically important crop in subtropical regions including Jahrom, Iran. Productivity of these fruit crops can severely decline due to biotic and abiotic stresses. Interactions were investigated between Hop Stunt Viroid (HSVd) infections and abiotic stress factors (drought and soil salinity) for effects on orchard decline. HSVd infection, a key biotic factor causing citrus cachexia, along with abiotic stresses of drought, high temperatures, and poor orchard management, compromise tree health by disrupting water balance and causing stunting and bark damage. Combined effects of HSVd infection and environmental stresses on citrus decline were assessed. Experimental treatments of healthy (experimental control), HSVd infected, abiotic decline- affected, and HSVd + abiotic decline was assessed in three citrus orchards. Compared with controls, trees from the other three treatments had reduced yields, plant heights, crown sizes, and fruit diameters. Plant heights varied among orchards, while fruit diameters did not. Healthy (control) plants grew and yielded best, while yields from plants infected with HSVd and subjected to climate change yielded least. Trees under climate-induced decline had increased fruit diameters, likely due to reduced fruit set under drought stress and redirected assimilates to reduced numbers of developing fruits. Similar responses have been reported in citrus under water stress conditions. Molecular diagnostics (RT-PCR and dot-blot hybridization) confirmed HSVd presence exclusively in symptomatic trees (samples of 10 trees per orchard), while assays for citrus Tristeza Virus (CTV) were negative. These results are consistent with HSVd being the primary biotic agent associated with the observed citrus decline, although causal confirmation requires controlled inoculation studies. Stresses negatively impacted citrus productivity in 85 orchards in Jahrom. Given the observed associations between HSVd presence, abiotic decline indicators, and reduced productivity, integrated citrus crop management is recommended. This should include reductions of drought (through optimized irrigation scheduling), and soil salinity (mitigation of sodium adsorption ratio), and appropriate phytosanitary measures. Phytosanitation should include use of certified viroid-free planting material, and targeted molecular surveillance for viroid infections. Implementation of these strategies should be guided by follow-up studies that verify absence/presence of other graft-transmissible pathogens, quantify rootstock effects, and test mitigation strategies in controlled and replicated field trials.
