Alternaria Species Research Articles

Alternaria arborescens and A. italica Causing Leaf Blotch on Celtis julianae in China.

Celtis julianae Schneid. is widely planted as a versatile tree species with ecological and economic significance. In September 2022, a leaf blotch disease of C. julianae was observed in Nanjing, Jiangsu, China, with an infection incidence of 63%. The disease led to severe early defoliation, significantly affecting the ornamental and ecological value of the host tree. The accurate identification of pathogens is imperative to conducting further research and advancing disease control. Koch's postulates confirmed that the fungal isolates (B1-B9) were pathogenic to C. julianae. The morphology of the characteristics of the pathogen matched those of Alternaria spp. The internal transcribed spacer region (ITS), large subunit (LSU) and small subunit (SSU) regions of rRNA, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Alternaria major allergen gene (Alt a 1), RNA polymerase second largest subunit (RPB2), and portions of translation elongation factor 1-alpha (TEF1-α) genes were sequenced. Based on multi-locus phylogenetic analyses and morphology, the pathogenic fungi were identified as Alternaria arborescens and A. italica. The findings provided useful information for disease management and enhanced the understanding of Alternaria species diversity in China. This is the first report of A. arborescens and A. italica causing leaf blotch of C. julianae in China and worldwide.

Four New Species of Small-Spored Alternaria Isolated from Solanum tuberosum and S. lycopersicum in China.

Small-spored Alternaria species have been frequently isolated from diseased leaves of Solanum plants. To clarify the diversity of small-spored Alternaria species, a total of 118 strains were obtained from leaf samples of S. tuberosum and S. lycopersicum in six provinces of China during 2022-2023. Based on morphological characterization and multi-locus phylogenetic analysis of the internal transcribed spacer of the rDNA region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1 alpha (TEF1), RNA polymerase second largest subunit (RPB2), Alternaria major allergen gene (Alt a 1), endopolygalacturonase gene (EndoPG) and an anonymous gene region (OPA10-2), seven species were determined, including four novel species and three known species (A. alternata, A. gossypina and A. arborescens). The novel species were described and illustrated as A. longxiensis sp. nov., A. lijiangensis sp. nov., A. lycopersici sp. nov. and A. solanicola sp. nov.. In addition, the pathogenicity of the seven species was evaluated on potato leaves. The species exhibited various aggressiveness, which could help in disease management.

Microbiology and Physicochemical Characteristics of Surface Water from a Local Refinery Site in Port Harcourt, Nigeria

Water plays a vital role in maintaining human health but due to an increase in industrialization, urbanization and other anthropogenic activities, surface water pollution is on an increase. This research was carried out to investigate the microbiological and physicochemical status of a crude oil polluted surface water in Iwofe River, Rumuolemini, Port Harcourt. Samples were collected from two points (Upstream and Downstream) bi-monthly for a period of three months. The THB counts for the upstream and downstream samples were 1.7 × 108cfu/ml and 1.4 × 108 cfu/ml, respectively while the THF counts for the samples were 3.0 × 106cfu/ml and 1.4 × 106 cfu/ml, respectively. Hydrocarbon utilizing bacterial (HUB) counts were higher in the upstream (1.5 × 106cfu/ml) than downstream (4.3 ×105cfu/ml) location of the Iwofe River. The Hydrocarbon utilizing fungal (HUF) count ranged from 1.0 × 105cfu/ml to 1.4 × 105 cfu/ml in the upstream and downstream water samples, respectively. The results of all the microbiological parameters analyzed indicated that the total heterotrophic bacterial (THB) and Total heterotrophic fungal (THF) counts were higher in the upstream than in the downstream location. The Most Probable Number (MPN) method used for the determination of coliform counts revealed the presence of coliforms both upstream and downstream, with an MPN index of 1,600/100ml of each sample. Some of the bacterial species isolated were Staphylococcus aureus, Escherichia coli and Vibrio cholerae while the fungal isolates included Aspergillus fumigatus, Penicillium species and Alternaria species. The high level of oil contamination poses a great health threat and there is a need for remediation of the aquatic ecosystem.

Enhancing plant defense using rhizobacteria in processing tomatoes: a bioprospecting approach to overcoming Early Blight and Alternaria toxins.

Plant growth-promoting rhizobacteria (PGPR) with antagonistic activity toward plant pathogenic fungi are valuable candidates for the development of novel plant protection products based on biocontrol activity. The very first step in the formulation of such products is to screen the potential effectiveness of the selected microorganism(s). In this study, non-pathogenic rhizobacteria were isolated from the rhizosphere of tomato plants and evaluated for their biocontrol activity against three species of mycotoxin-producing Alternaria. The assessment of their biocontrol potential involved investigating both fungal biomass and Alternaria toxin reduction. A ranking system developed allowed for the identification of the 12 best-performing strains among the initial 85 isolates. Several rhizobacteria showed a significant reduction in fungal biomass (up to 76%) and/or mycotoxin production (up to 99.7%). Moreover, the same isolates also demonstrated plant growth-promoting (PGP) traits such as siderophore or IAA production, inorganic phosphate solubilization, and nitrogen fixation, confirming the multifaceted properties of PGPRs. Bacillus species, particularly B. amyloliquefaciens and two strains of B. subtilis, showed the highest efficacy in reducing fungal biomass and were also effective in lowering mycotoxin production. Isolates such as Enterobacter ludwigii, Enterobacter asburiae, Serratia nematodiphila, Pantoea agglomerans, and Kosakonia cowanii showed moderate efficacy. Results suggest that by leveraging the diverse capabilities of different microbial strains, a consortium-based approach would provide a broader spectrum of effectiveness, thereby signaling a more encouraging resolution for sustainable agriculture and addressing the multifaceted nature of crop-related biotic challenges.

Sustainable Potato Growth under Straw Mulching Practices

Extreme heat, droughts, pests, diseases, and short bursts of heavy rain make potato production unsustainable. This unfavorable environment negatively affects potato productivity and yield levels. Within the next few years, conditions will likely deteriorate even more. In potato cultivation, straw mulching has been shown to increase yields by promoting the growth of beneficial bacteria in the soil. Mulching improves soil humidity, decreases transpiration, and cools the soil in dry and hot regions. There is a global decline in potato yields per hectare due to poor nutrient management, moderately humid years, and high disease pressure caused by Phytophthora infestans and Alternaria species. Farmers must take cultivation measures to achieve economic efficiency and adequate yields. A range of practices contributes to better potato yields and productivity, such as the use of appropriate fungicides, planting high-yielding varieties, and increasing row spacing. These practices complicate cultivation and affect profits. Furthermore, inorganic nitrogen in the soil regularly causes acidification, eroding soil fertility. As a result of land preparation, straw residues from rice and maize are collected from the field and destroyed or burned, which depletes nutrients and pollutes the air. Returning these residues to the soil, however, can improve its quality. Integrating rice and maize straw mulching into potato cultivation practices can enhance agricultural sustainability, productivity, and yield. This review will focus on using rice and maize straw mulching in cultivating potatoes. Straw mulching promotes sustainable potato growth, increasing productivity and quality while minimizing reliance on chemical inputs. Such practices can mitigate the need for synthetic fertilizers to enhance sustainable agriculture, ensure long-term growth, improve soil health, increase yields, and promote sustainable agriculture.

Identification, characterization, and expression analysis of PpCPK gene family in response to Alternaria-infected peach fruits collected from different geographical regions of China

Peach is a popular and economically important fruit tree highly susceptible to biotic and abiotic stresses, including diseases caused by fungi, bacteria and viruses, pests and insects that feed fruits and leaves. Alteranria is a deadly disease agent, a genus of fungi that can cause significant damage to plants and crops such as peaches. Here, we investigated the role of CPK genes against in Alternaria species. The calcium-dependent protein kinase (CPK) gene family plays a vital role in the biotic stress response of plants. In this study, we aimed to identify, characterize, and analyze the expression pattern of the PpCPK gene family in response to Alternaria-infected peach fruits collected from different geographical regions of China. Based on phylogenetic analysis, 17 PpCPK genes were identified and classified into seven groups. The physicochemical properties, gene structure, conserved domains, and motifs of the PpCPK genes were analyzed to understand their molecular characteristics further. The Ka/Ks ratio analysis revealed the evolutionary facets of duplication events of PpCPKs and predicted the divergence time between 23.5 and 43.6 million years ago. The promoter region analysis confirmed the presence of plant growth, light, stress, and hormone-related cis-elements in PpCPKs. Additionally, the expression pattern of PpCPKs was analyzed using real-time quantitative PCR in Alternaria-infected peach fruits from different regions of China. The results indicated a differential expression pattern of PpCPK genes responding to Alternaria infection, suggesting their potential role in defense against biotic stress. Overall, our study provides insights into the molecular mechanisms of PpCPK genes in response to biotic stress, which could aid in developing strategies for improving peach resistance to biotic stress.

Scope of Onsite, Portable Prevention Diagnostic Strategies for Alternaria Infections in Medicinal Plants.

Medicinal plants are constantly challenged by different biotic inconveniences, which not only cause yield and economic losses but also affect the quality of products derived from them. Among them, Alternaria pathogens are one of the harmful fungal pathogens in medicinal plants across the globe. Therefore, a fast and accurate detection method in the early stage is needed to avoid significant economic losses. Although traditional methods are available to detect Alternaria, they are more time-consuming and costly and need good expertise. Nevertheless, numerous biochemical- and molecular-based techniques are available for the detection of plant diseases, but their efficacy is constrained by differences in their accuracy, specificity, sensitivity, dependability, and speed in addition to being unsuitable for direct on-field studies. Considering the effect of Alternaria on medicinal plants, the development of novel and early detection measures is required to detect causal Alternaria species accurately, sensitively, and rapidly that can be further applied in fields to speed up the advancement process in detection strategies. In this regard, nanotechnology can be employed to develop portable biosensors suitable for early and correct pathogenic disease detection on the field. It also provides an efficient future scope to convert innovative nanoparticle-derived fabricated biomolecules and biosensor approaches in the diagnostics of disease-causing pathogens in important medicinal plants. In this review, we summarize the traditional methods, including immunological and molecular methods, utilized in plant-disease diagnostics. We also brief advanced automobile and efficient sensing technologies for diagnostics. Here we are proposing an idea with a focus on the development of electrochemical and/or colorimetric properties-based nano-biosensors that could be useful in the early detection of Alternaria and other plant pathogens in important medicinal plants. In addition, we discuss challenges faced during the fabrication of biosensors and new capabilities of the technology that provide information regarding disease management strategies.

Draft Genome Sequence of Carrot Alternaria Leaf Blight Pathogen Alternaria dauci.

The fungal genus Alternaria, which causes a variety of crop diseases, is widely distributed in the world. Alternaria leaf blight, caused by Alternaria dauci, is one of the most common and destructive diseases in carrot. The infection of A. dauci leads to dramatic decay on both foliage and taproot in severe cases, which results in significant yield losses. In this study, we sequenced and assembled the genome of A. dauci isolate CALB1, which isolated from the major carrot producing areas of China. A total of 65 contigs were assembled, and the estimated genome size was 34.9 Mb. The draft genome of A. dauci can be used for comparative genomic analysis of Alternaria species and provide genetic information for further research on plant-pathogen interactions.

Isolation and Identification of Wheat Seed Fungi and Effect of Microwave on Fungi Loads in Salah Al-Din Governorate in Iraq

This study was conducted to determine the seed borne fungi of wheat cultivars in the seed production stores companies in Salah AL-Din Governorate, Iraq, 2021, and then evaluate the efficiency of Microwaves to kill or eliminate the fungal pathogens of wheat. The results of the study indicate that all samples of wheat seeds were contaminated with fungi in different percentage. 318 isolates of fungi were isolated from the studied wheat seed samples.They were identified culturally and microscopically according to approved taxonomic keys. The fungus A. flavus appeared with a percentage of 100 %, as it was present in all samples of the studied wheat seeds, as well as the species of A.niger. Then the species of Alternaria (A.alternata, A.tenuissima , A.saponaria) and the species of Aspergillus ( A.flavus , A.fumigatus, A.terrus, A.niger), Rhizopus oryzae, Rhizoctonia solani, Penicillium spp, Aureobasidium pullulans, Phoma spp, Curvularia lunata, Stemphylium spp, and Mucor spp appeared with different percentages. an investigation into the effect of microwaves on fungal pathogens of wheat varieties was undertaken .This was achived by microwaving seeds at 0 , 10 , 20 , 30 and 40 Seconds . Agar plate tests were used to ass’s pathogen loads. Pathogen levels were steadialy reduced at all treatment times and by 30 S treatment. All pathogens were consistently destroyed. In comparison, at 40 S the levels of saprophytic fungi were increased because it thermotolerant. The use of microwave radiation was a valuable tool for crop improvement, it was rapid, economic, efficient and safe to eradicating the pathogens.

Structure elucidation and biological activities of perylenequinones from an Alternaria species

The KEAP1-Nrf2/ARE pathway is a pivotal cytoprotective regulator against oxidative stress which plays an important role in the development of many inflammatory diseases and cancer. Activation of the Nrf2 transcription factor by oxidative stress or electrophiles regulates antioxidant response element (ARE)-dependent transcription of antioxidative, detoxifying, and anti-inflammatory proteins. Therefore, modulators of the KEAP1-Nrf2/ARE pathway have received considerable interest as therapeutics to protect against diseases where oxidative stress constitutes the underlying pathophysiology. In a search for fungal secondary metabolites affecting the Nrf2/ARE-dependent expression of a luciferase reporter gene in BEAS-2B cells, three new perylenequinones, compounds 1, 2, and 3, together with altertoxin-I (ATX-I), were isolated from fermentations of an Alternaria species. The structures of the compounds were elucidated by a combination of one- and two-dimensional NMR spectroscopy and mass spectrometry. Compound 1 and ATX-I exhibited strong cytotoxic effects with LC50-values of 3.8 µM and 6.43 µM, respectively, whereas compound 3 showed no cytotoxic effects up to 100 µM on BEAS-2B cells. ATX-I induced ARE-dependent luciferase expression approximately fivefold and compound 1 approximately 2.6-fold at a concentration of 3 µM in transiently transfected BEAS-2B cells. In addition, compound 1 and ATX-I exhibited strong oxidative effects, whereas compound 3 did not show significant oxidative properties. For compound 1 and ATX-I, a strong upregulation of heme oxygenase-1 could be observed on mRNA and protein level in treated BEAS-2B cells. Moreover, compound 3 significantly decreased sod3 mRNA levels after induction of oxidative stress with benzoquinone.

Diversity of Mycotoxins and Other Secondary Metabolites Recovered from Blood Oranges Infected by Colletotrichum, Alternaria, and Penicillium Species.

This study identified secondary metabolites produced by Alternaria alternata, Colletotrichum gloeosporioides, and Penicillium digitatum in fruits of two blood orange cultivars before harvest. Analysis was performed by UHPLC-Q-TOF-MS. Three types of fruits were selected, asymptomatic, symptomatic showing necrotic lesions caused by hail, and mummified. Extracts from peel and juice were analyzed separately. Penicillium digitatum was the prevalent species recovered from mummified and hail-injured fruits. Among 47 secondary metabolites identified, 16, 18, and 13 were of A. alternata, C. gloeosporioides, and P. digitatum, respectively. Consistently with isolations, indicating the presence of these fungi also in asymptomatic fruits, the metabolic profiles of the peel of hail-injured and asymptomatic fruits did not differ substantially. Major differences were found in the profiles of juice from hail-injured and mummified fruits, such as a significant higher presence of 5,4-dihydroxy-3,7,8-trimethoxy-6C-methylflavone and Atrovenetin, particularly in the juice of mummified fruits of the Tarocco Lempso cultivar. Moreover, the mycotoxins patulin and Rubratoxin B were detected exclusively in mummified fruits. Patulin was detected in both the juice and peel, with a higher relative abundance in the juice, while Rubratoxin B was detected only in the juice. These findings provide basic information for evaluating and preventing the risk of contamination by mycotoxins in the citrus fresh fruit supply chain and juice industry.

Biocontrol efficacy of Wickerhamomyces anomalus on tomato field diseases and study of the relevant mechanisms via microbiome analysis

Tomatoes (Solanum lycopersicum L.) are vulnerable to infections by pathogens found in a complex environment. Most of these infections are triggered by an imbalance between plant microorganisms and pathogens, leading to various tomato rots and high economic losses. This study aims to test the biocontrol ability of an antagonistic yeast, Wickerhamomyces anomalus, towards gray mold disease in tomatoes in the field and explore the relevant mechanisms through microbiome analysis of the microbial community on the surface of tomatoes. The results showed that W. anomalus decreased the tomato disease severity index during plant growth period, along with some changes in the microorganism community composition, including the increase of the abundance of some plant growth promotion bacteria such as Pantoea sp. and Pseudomonas sp. and biocontrol agents such as Golubevia sp. and Papiliotrema sp., and abundance decrease in some potential pathogens such as species of Alternaria. All these results suggest that W. anomalus could control tomato diseases in the field and the regulation in microorganism composition might be a possible mechanism.

Molecular Identification and Genetic Diversity of Alternaria Isolates Causing Leaf Spot Disease in Cotton from Major Cotton Growing Areas of South Zone of India

Background: Alternaria leaf spot caused by two species namely Alternaria macrospora and Alternaria alternata is an important foliar disease of cotton. Conidial morphology showed that most of the isolates in the study belonged to A. macrospora. Molecular confirmation is necessary to strengthen the identification of species in Alternaria. Genetic diversity study of Alternaria isolates using ISSR and hyper variable SSR primers will provide variation and grouping among the isolates collected from major areas of South Zone of India. Present study was conducted to identify Alternaria isolates at species level using molecular methods (species specific primers) and genetic diversity analysis using ITS, SSR and ISSR primers. Methods: Reported species-specific primers such as AmF and AmR as well as AaF2 and AaF3 were used for Alternaria species identification. ITS region was amplified through ITS1 and ITS4 and sequences were used for identification and clustering of isolates. Thirteen hyper variable SSR primers specific to Alternaria were designed based on the sequences retrieved from NCBI and used for diversity study. Six different ISSR primers were also used for genetic diversity study. Result: Reported species-specific primers found not suitable to identify A. macrospora and A. alternata at species level. Two SSR primers were found to be effective in showing variability among the isolates. Six clusters were formed at 71 percent genetic dissimilarity among 15 isolates of Alternaria through ISSR primers. Five clusters were formed in ITS sequence’s diversity analysis. Blasting of ITS sequences of 15 selected isolates at NCBI showed that all belong to A. alternata. This was due to absence or presence of very few sequences of A. macrospora in NCBI database itself. Further house-keeping genes like Alt a1, Plasma membrane ATPase, GAPDH and TEF -1 α sequence analysis will be useful for confirmation of A. macrospora at species level.

Melanonychia and subungual papule in a middle-aged man

Melanonychia and subungual papule in a middle-aged man

Species diversity and molecular characterization of Alternaria section Alternaria isolates collected mainly from cereal crops in Canada.

Alternaria is often one on the most abundant fungal genera recovered from a wide array of plant hosts and environmental substrates. Many species within the sub-generic Alternaria section Alternaria are common plant pathogens that cause pre-harvest losses due to reduced productivity and post-harvest losses due to spoilage and contamination with mycotoxins. As certain species of Alternaria may have distinct mycotoxin profiles, and very broad host ranges, understanding the distribution of species by geography and host is critical for disease prediction, toxicological risk assessment, and guiding regulatory decisions. In two previous reports, we performed phylogenomic analyses to identify highly informative molecular markers for Alternaria section Alternaria, and validated their diagnostic ability. Here, we perform molecular characterization of 558 section Alternaria strains, collected from 64 host genera in 12 countries, using two of these section-specific loci (ASA-10 and ASA-19) along with the RNA polymerase II second largest subunit (rpb2) gene. The majority of strains (57.4%) originated from various cereal crops in Canada, which formed the main focus of our study. Phylogenetic analyses were used to classify strains into section Alternaria species/lineages, demonstrating that the most common species on Canadian cereal crops are Alternaria alternata and A. arborescens. Further population genetic analyses were consistent with A. alternata being a widely distributed species with relatively low levels of geographic isolation (i.e., Canadian isolates did not form distinct clades when compared to other regions). Our expanded sampling of A. arborescens has greatly increased the known diversity of this group, with A. arborescens isolates forming at least three distinct phylogenetic lineages. Proportionally, A. arborescens is more prevalent in Eastern Canada than in Western Canada. Sequence analyses, putative hybrids, and mating-type distributions provided some evidence for recombination events, both within and between species. There was little evidence for associations between hosts and genetic haplotypes of A. alternata or A. arborescens.

Development of a real-time PCR and multiplex PCR assay for the detection and identification of mycotoxigenic fungi in stored maize grains

ABSTRACT This study aimed to identify important mycotoxigenic fungi and accurate detection of mycotoxin in stored maize grains using molecular methods. The current study also optimised the real-time PCR (RT-PCR) assay. The melting curve was established to identify isolated fungal species of Aspergillus (4), Fusarium (3), Penicillium (3), and Alternaria (one). A multiplex polymerase chain reaction (mPCR) technique was developed for the detection and characterisation of mycotoxin producing fungi, mycotoxin metabolic pathway genes, and the determination of eleven mycotoxins in stored maize grains using high-performance liquid chromatography (HPLC). The mPCR results indicated positive signals for potentially mycotoxigenic fungal species tested of Aspergillus, Fusarium, Penicillium, and Alternaria. A protocol for multiplex reverse transcription-polymerase chain reaction (mRT-PCR) was tested to distinguish between free and contaminated, stored maize with aflatoxin B1 (AFB1). The expression pattern of four aflatoxin biosynthetic pathway genes, AFB1 (aflQ, aflP, aflO, and aflD), was a good marker for contaminated, stored maize grains. HPLC analysis showed that maize grain samples were contaminated with mycotoxins, and the concentration was above the detection level. The results indicate that the polyphasic approach might provide a sensitive, rapid, and accurate method for detecting and identifying mycotoxigenic fungal species and mycotoxins in stored maize grains.

Fungicide-free management of Alternaria leaf blotch and fruit spot on apple indicates Alternaria spp. as secondary colonizer

The fungal genus Alternaria is a pan-global pathogen of > 100 crops, and is associated with the globally expanding Alternaria leaf blotch in apple (Malus x domestica Borkh.) which leads to severe leaf necrosis, premature defoliation, and large economic losses. Up to date, the epidemiology of many Alternaria species is still not resolved as they can be saprophytic, parasitic or shift between both lifestyles and are also classified as primary pathogen able to infect healthy tissue. We argue that Alternaria spp. does not act as primary pathogen, but only as a necrosis-dependent opportunist. We studied the infection biology of Alternaria spp. under controlled conditions and monitored disease prevalence in real orchards and validated our ideas by applying fungicide-free treatments in 3-years field experiments. Alternaria spp. isolates were not able to induce necroses in healthy tissue, but only when prior induced damages existed. Next, leaf-applied fertilizers, without fungicidal effect, reduced Alternaria-associated symptoms (− 72.7%, SE: ± 2.5%) with the same efficacy as fungicides. Finally, low leaf magnesium, sulphur, and manganese concentrations were consistently linked with Alternaria-associated leaf blotch. Fruit spot incidence correlated positively with leaf blotch, was also reduced by fertilizer treatments, and did not expand during storage unlike other fungus-mediated diseases. Our findings suggest that Alternaria spp. may be a consequence of leaf blotch rather than its primary cause, as it appears to colonize the physiologically induced leaf blotch. Taking into account existing observations that Alternaria infection is connected to weakened hosts, the distinction may appear slight, but is of great significance, as we can now (a) explain the mechanism of how different stresses result in colonization with Alternaria spp. and (b) substitute fungicides for a basic leaf fertilizer. Therefore, our findings can result in significant decreases in environmental costs due to reduced fungicide use, especially if the same mechanism applies to other crops.

Using qPCR and microscopy to assess the impact of harvesting and weather conditions on the relationship between Alternaria alternata and Alternaria spp. spores in rural and urban atmospheres

Alternaria is a plant pathogen and human allergen. Alternaria alternata is one of the most abundant fungal spores in the air. The purpose of this study was to examine whether Alternaria spp. spore concentrations can be used to predict the abundance and spatio-temporal pattern of A. alternata spores in the air. This was investigated by testing the hypothesis that A. alternata dominates airborne Alternaria spp. spores and varies spatio-temporally. Secondarily, we aimed at investigating the relationship between airborne Alternaria spp. spores and the DNA profile of A. alternata spores between two proximate (~ 7 km apart) sites. These were examined by sampling Alternaria spp. spores using Burkard 7-day and cyclone samplers for the period 2016–2018 at Worcester and Lakeside campuses of the University of Worcester, UK. Daily Alternaria spp. spores from the Burkard traps were identified using optical microscopy whilst A. alternata from the cyclone samples was detected and quantified using quantitative polymerase chain reaction (qPCR). The results showed that either A. alternata or other Alternaria species spores dominate the airborne Alternaria spore concentrations, generally depending on weather conditions. Furthermore, although Alternaria spp. spore concentrations were similar for the two proximate sites, A. alternata spore concentrations significantly varied for those sites and it is highly likely that the airborne samples contained large amounts of small fragments of A. alternata. Overall, the study shows that there is a higher abundance of airborne Alternaria allergen than reported by aerobiological networks and the majority is likely to be from spore and hyphal fragments.

Small-spored Alternaria spp. (section Alternaria) are common pathogens on wild tomato species.

The wild relatives of modern tomato crops are native to South America. These plants occur in habitats as different as the Andes and the Atacama Desert and are, to some degree, all susceptible to fungal pathogens of the genus Alternaria. Alternaria is a large genus. On tomatoes, several species cause early blight, leaf spots and other diseases. We collected Alternaria-like infection lesions from the leaves of eight wild tomato species from Chile and Peru. Using molecular barcoding markers, we characterized the pathogens. The infection lesions were caused predominantly by small-spored species of Alternaria of the section Alternaria, like A. alternata, but also by Stemphylium spp., Alternaria spp. from the section Ulocladioides and other related species. Morphological observations and an infection assay confirmed this. Comparative genetic diversity analyses show a larger diversity in this wild system than in studies of cultivated Solanum species. As A. alternata has been reported to be an increasing problem in cultivated tomatoes, investigating the evolutionary potential of this pathogen is not only interesting to scientists studying wild plant pathosystems. It could also inform crop protection and breeding programs to be aware of potential epidemics caused by species still confined to South America.

Leaf spot of Lonicera japonica Thunb. (honeysuckle) caused by Alternaria alternata newly reported in China

Lonicera japonica Thunb. (honeysuckle) is widely cultivated as a medicinal herb in China. In recent years, the crop has been affected by a leaf spot disease in Suiyang, Guizhou, China. Disease symptoms included necrotic spots and wilting on leaves. The pathogen responsible for the disease was successfully isolated from symptomatic leaf tissue and identified. Identification based on morphological characteristics suggested that all the recovered fungal isolates belonged to small-spored Alternaria species. Multilocus sequence analyses of the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), endopolygalacturonase (endoPG), translation elongation factor 1-alpha (tef1), and Alternaria major allergen (Alt a 1) genes, assigned five selected isolates as belonging to Alternaria alternata. Pathogenicity assays confirmed the Alternaria alternata species caused the observed symptoms. To our knowledge, this is the first report of honeysuckle leaf spot caused by A. alternata in China. The results of this study advance our understanding of honeysuckle leaf spot in China and lay the groundwork for developing efficient pre- and post-harvest control measures to stop the spread of the disease.