Alternaria Infection Research Articles

Development of cracks in early-harvested persimmon cultivar and their reduction by preharvest treatments

ABSTRACT Diospyros Kaki Cv (Qiyuezao) 117 is an early ripening persimmon cultivar, ready to be harvested in August. One of the pitfalls of this cultivar is the development of cracks on its surface. These cracks turn brown after astringency removal, preventing the commercialisation of this cultivar. Pre-harvest treatment with Superlon™ (containing benzyl adenine (BA) + gibberellic acid (GA4+7) at 40 mg/L of each) or Turbo™ (containing Thidiazuron (TDZ) at 5 mg/L) reduced cracks of different maturity fruit (green, green orange, and orange fruit) at harvest and following 5 days of astringency removal. Cracks remained low in the Plant growth regulators (PGRs)-treated fruit also following three months of storage. The PGRs treatments also reduced damage and Alternaria infection, developed during storage. Although fruit lost their firmness during storage, the PGRs-treated fruit remained firmer. Both PGRs treatments increased the number of cells in the peel. Thidiazuron was as effective as BA+GA4+7 treatment at eight times lower concentration of each of the compounds. Hence, in-orchard TDZ treatment can be used to reduce persimmon cracks.

A Rare Case of Symmetrical Cutaneous Alternaria Infections after Bilateral Lung Transplant

Introduction Lung transplant recipients are prone to opportunistic infections like fungi in view of the high levels of sustained immunosuppression required to avoid graft rejection. We report an unusual fungal pathogen, Alternaria, presenting with bilateral, cutaneous lesions with an atypical morphology. Case Report A 73-year-old male underwent bilateral lung transplantation in October 2017 for idiopathic pulmonary fibrosis with basiliximab induction. The patient was on typical three-drug immunosuppression of tacrolimus (goal trough 7-8ng/ml), prednisone, and mycophenolate mofetil (lower dose 250mg bid). At his one year follow up, he was noted to have symmetrical, keratotic lesions on both lower extremities. The patient reported no traumatic source, except for fire ant bites or minor scratches while gardening. Punch biopsies were performed and histopathology revealed epidermal hyperplasia with associated underlying granulomatous host response. After assessing morphology and Fontana masson stain, a differential of Blastomyces species was favored over Cryptococcus. However, serum tests were negative for Blastomyces and fungal cultures from the biopsy grew Alternaria. Given non-contiguous sites and concern for dissemination, a chest CT was performed, but did not note changes consistent with pulmonary involvement. He was treated with posaconazole (300mg daily) for a 3-month regimen with a decrease of tacrolimus levels. With noted regression of nodules after three months, posaconazole was stopped. A year later, a recurrence of Alternaria appeared on his lower extremities, distal to the previous infections, with the same raised violaceous appearance. Treatment with posaconazole (200mg daily) was initiated. Due to recurrence, mycophenolate was halted and serum tacrolimus levels were targeted lower. After 6 months, posaconazole was stopped as the lesions had healed. Summary Our path to diagnosis in this case highlights the challenges in confirming infectious species by histopathology alone and hence the importance of culture and molecular diagnosis. This case was particularly unusual with the presentation of symmetrical lower extremity lesions as it was not clear if this represented dual inoculation or a disseminated infection. A high level of suspicion needs to be maintained for lesser known fungal pathogens, like Alternaria, in highly immunocompromised hosts.

Enhancement in serum (1–3)-β-D-glucan level by cutaneous alternariosis: A case report and literature review

Contamination with the fungus Alternaria spp. is often considered to have originated from laboratory sources, which occasionally causes infection in immunocompromised patients, termed as phaeohyphomycosis. Here, we have reported a case of cutaneous alternariosis caused by Alternaria alternata. This diagnosis was based on microscopic examination and mycological culturing of patient's vesicular lesions, with the use of 5 molecular markers (namely, ITS, ATPase, Actin, rpb2, and tef1) for strain identification. We noted that Alternaria infection caused an increase in the serum level of (1–3)-β-D-glucan (BG) in the patients. To the best of our knowledge, no such finding has been reported in previously in the literature.

Thiabendazole vs difenoconazole in chemical control of seed-borne toxigenic fungi affecting wheat quality

Two common fungicides: Vial TrasT (60 g/l tebuconazole and 80 g/l thiabendazole) and Oplot (90 g/l difenoconazole and 45 g/l tebuconazole) were tested for effectiveness against seed-borne toxigenic fungi Fusarium spp. and Alternaria spp. using naturally infected wheat (Triricum aestivum L., cultivar Novosibirskaya-14) seeds collected from the field located near Krasnoyarsk, Russia. Treatment with Oplot statistically significantly reduced Fusarium infection by 10 percentage points (from 31.4% to 21.4%) and statistically significantly reduced Alternaria infection by 25.8 percentage points (from 42.9% to 17.1%). Treatment with Vial TrasT demonstrated no statistically significant effect in reducing infection both for Fusarium and Alternaria. The results demonstrates that populations of Fusarium spp. and Alternaria spp. in Middle Siberia have developed resistance to tebuconazole and thiabendazole, but not to difenoconazole.

Diversity of foliar endophytes in a dioecious wild grass and their interaction with the systemic Epichloë

Abstract This study compares the culturable fungal endophytic community inhabiting leaves of Epichloe-infected (E+) and Epichloe-free (E-) plants of Poa bonariensis. Plants were collected from a wild population (dioecious species) where E+ and E- plants co-exist. Fungal endophytes were isolated and then morphology and ribosomal DNA internal transcribed spacer sequences were used for the identification of isolates. In total 24 different taxa of non-Epichloe (NE) endophytes were identified. No significant differences were found in richness and diversity indexes of NE-endophytes between E+ and E- plants, or between pistillate (P) and staminate (S) plants. When we analyzed these effects based on the count of the most abundant genera, Alternaria and Stemphylium infection frequencies decreased in S plants, while in E+ plants, this tendency was observed for Alternaria. Our results suggest that Epichloe and the sex of the host plant may modulate some of the dominant foliar endophytic fungal taxa.

Characterization of mycotoxigenic Alternaria species isolated from the Tunisian halophyte Cakile maritima

Cakile maritima is a typical halophyte of the Mediterranean coasts. In addition to its ecological and industrial properties, C. maritima has antiscorbutic, diuretic and purgative roles in folk remedies. This plant is infected by different fungal species, mainly belonging to Alternaria genus. Two-hundred Alternaria strains were collected from four different pedo-climatic areas in Tunisia, from C. maritima fresh plant tissues showing symptoms of Alternaria infection. Phylogenetic analyses of 79 representative Alternaria strains, were carried out using multi-locus gene sequencing. All the strains clustered in the Alternaria Section: 47 strains had high homology with A. alternata reference strain, 13 grouped with A. arborescens reference strain, 12 grouped with A. mali reference strain, and seven strains were not well defined with A. mali as their closest species. In vitro production of tenuazonic acid (TA), alternariol (AOH), alternariol-monomethyl ether (AME), and altenuene (ALT) was evaluated. Approx. 68% of strains simultaneously produced AOH, AME and TA. Only two A. alternata and one A. mali strains were ALT producing. Pathogenicity tests on leaves of C. maritima were carried out with 41 representative strains. Alternaria arborescens showed the greatest pathogenicity compared to A. alternata and A. mali, although no statistically significant differences in pathogenicity were observed. This is the first study on Tunisian populations of Alternaria species isolated from the extremophile C. maritima.

Protection by some plant methanol extracts of cherry tomatoes (Solanum lycopersicum var. Cerasiforme) from fungic infection by Alternaria alternata

Cherry tomato is very susceptible to fungal infections that can cause considerable damage in crops and during storage. Alternaria infection is one of the most common and dangerous alterations for this fruit. They are caused by Alternaria alternata or some other species belonging to the same genus. In this work, we tested the antifungal activity of methanol extracts from five plants harvested in the region of Jijel (Algeria) on A. alternata. The activity was first tested in vitro and then on greenhouse cherry tomato plants: extracts were applied to healthy plants before infection in order to test their preventive action, and after infection to determine whether they are able to knock out Alternaria. Results showed that Rosmarinus officinalis and Lavandula angustifolia extracts were the most active in vitro on A. alternata. Microscopic observations of the mold indicated that these extracts inhibited the dictyospores production. The antifungal activity tested on the plants grown in greenhouse revealed that R. officinalis extract still was the most active. Extracts of L. angustifolia and Punica granatum did not protect the plants from Alternaria infection, but provided a total cure at the end of the treatment. Extracts from Quercus suber and Eucalyptus globulus were the least active. They did not bestow any protection nor complete healing of the plants. Dictyospores counting on fruits at the end of the treatment confirmed the results obtained for the greenhouse crops.

In-field detection of Alternaria solani in potato crops using hyperspectral imaging

Automatic detection of early blight caused by Alternaria solani could promote a drastic reduction in the consumption of plant protection agents and the related production losses. A proximal sensing platform was constructed and calibrated for acquiring high resolution hyperspectral images in the field, and used to accurately map Alternaria lesions. High resolution canopy reflectance images were obtained for 32 potato plants that had been infected with A. solani and 32 healthy reference plants. Spectral classifiers like partial least squares discriminant analysis (PLS-DA) and support vector machines (SVM) based on PCA scores were tested to discriminate affected and non-affected pixels. Both spectral classifiers performed well at pixel level with accuracies above 0.92. The NIR region (750 nm) was identified as the most discriminative part of the spectrum for detecting the lesions. As the disease pressure is typically expressed as the number of lesions per area, the accuracy was also evaluated at this level. This indicated a considerable number of false detections at the edges of the leaves and the leaf axils. Therefore, a decision tree was designed based on expert knowledge about the shape of Alternaria lesions, and used to post-process the classified images. This reduced the number of false detections, increasing the precision from 0.17 to 0.22 at the expense of a reduction in recall from 0.88 to 0.84. This leaves considerable room for improvement in the classification accuracy at the object level. We learned that (1) few, broad wavelengths are sufficient and (2) spatial context is essential for the detection of lesions caused by Alternaria infection. The application of more powerful object classification techniques such as convolutional neural networks to enhance the model performance by efficiently encapsulating the spatial context in the classifier might further improve the detection performance. This could pave the way to UAV or tractor based Alternaria mapping.

A combined transcriptional, biochemical and histopathological study unravels the complexity of Alternaria resistance and susceptibility in Brassica coenospecies

Alternaria blight is one of the most devastating diseases of rapeseed-mustard caused by a necrotrophic fungus Alternaria brassicae. Lack of satisfactory resistance resource in Brassica is still a main obstruction for developing resistance against Alternaria. In this study, we have selected Brassica juncea, Sinapis alba and Camelina sativa to understand and unravel the mechanism of disease resistance against Alternaria. Histopathological studies showed early onset of necrosis in B. juncea (1 dpi) and delayed in S. alba (2 dpi) and C. sativa (3 dpi) respectively. Early and enhanced production of hydrogen peroxide (H2O2) was observed in C. sativa and S. alba (6 hpi) when compared to B. juncea (12 hpi). An increase in catalase activity was observed in both C. sativa (36 % at 6 hpi) and S. alba (15 % at 12 hpi), whereas it significantly decreased in B. juncea at 6 hpi (23 %), 12 hpi (30 %) and 24 hpi (8 %). Gene expression analysis showed induction of PR-3 and PR-12 genes only in C. sativa and S. alba when compared to B. juncea suggesting their vital role for Alternaria resistance. In contrast, SA marker genes were significantly expressed in B. juncea only which provides evidence of hormonal cross talk in B. juncea during Alternaria infection thereby increasing its susceptibility.

The Fate of Altertoxin II During Tomato Processing Steps at a Laboratory Scale.

Among various agricultural crops, tomatoes are particularly prone to Alternaria infections, which are frequently resulting in economic losses and mycotoxin contamination. To investigate potential health concerns implied for consumers, we simulated the storage and food processing steps of intact and blended tomatoes after addition of the highly genotoxic secondary metabolite altertoxin II. We observed a significant decrease in altertoxin II concentrations in samples stored at room temperature and particularly those undergoing thermal treatment by employing a validated LC-MS/MS method. When kept at room temperature, 87–90% of ATX-II was recovered after 1.5 h in raw tomato purees and purees heated before ATX-II addition, and 47–49% were recovered after 24 h. In intact tomato fruits the recovery was 23% after 1.5 h and <1% after 24 h. In heated purees (100°C for 30 min after ATX-II addition), also only minor concentrations accounting for 2-4% were determined. Moreover, the reduction of the compound's epoxide group to the alcohol, i.e., the formation of altertoxin I was demonstrated in intact tomato fruits (7–12%), suggesting enzymatic biotransformation of the xenobiotic by the plant's metabolism.

Onset of disseminated cutaneous nodules following toe amputation in heart transplant patient

Alternaria spp. infections are rare, but organ transplant recipients and immunosuppressed patients are particularly at risk of developing cutaneous alternariosis. Although cutaneous alternariosis is well-defined, instances of disseminated infection are exceedingly rare. We report a case of disseminated Alternaria infection in an immunocompromised patient from a primary focus of ungual phaeohyphomycosis.

Characterization of defense responses in the ‘green ring’ and ‘red ring’ on jujube fruit upon postharvest infection by Alternaria alternata and the activation by the elicitor treatment

Alternaria alternata is the major threat to postharvest storage of jujube (Ziziphus jujuba Mill.) fruit. A typical phenotype that a ‘red ring’ circling an enclosed ‘green ring’ area surrounding the spot of Alternaria rot on the jujube peel was first found and investigated in this study. Results indicated that the pathogenic infection is essential for the onset and development of the phenotype on jujubes, with high inoculum concentration and low incubation temperature leading to the enlarged ‘green ring’. The boundary line between the two rings seemed to be pre-fixed on the A. alternata-infected jujubes once the phenotype appeared. The ‘green ring’ was invaded gradually and ‘eaten-up’ eventually by the expansion of the surrounded rot spot. Biochemical measurements showed that such successful infection on jujubes might attribute to the great loss of individual phenolic compounds, including (+)-catechin, chlorogenic acid, (−)-epicatechin and p-coumaric acid, in the peel tissue of the ‘green ring’ and ‘red ring’, while some antifungal compounds increased in the flesh beneath the peel tissue in response to the infection. The elicitor salicylic acid (SA) triggered the early and rapid occurrence of the ‘green ring’ and ‘red ring’ on the A. alternata-infected jujubes. The SA treatment activated the phenylpropanoid pathway and elevated the accumulation of total phenolic compounds in the ‘green ring’ to combat the fungal attack and thereby restrict the expansion of disease lesion. Characterization of defense responses in the ‘green ring’ and ‘red ring’ on jujubes against Alternaria infection is helpful for unravelling the underlying mechanisms of the formation of defense resistance in fruit upon postharvest infection.

Impact of Alternaria spp. and Alternaria Toxins on Quality of Spelt Wheat

There is an increasing consumer demand for alternative cereals nowadays. Spelt wheat (Triticum aestivum ssp. Spelta) appears to be a future source for the agriculture and food sector. Alternaria spp. infections might become a serious danger to the worldwide grain industry, resulting in yield losses and reduction of end-use quality, with potential harmful effect of Alternaria toxins on human and animal health. This paper presents the first assessment of the impact of Alternaria infection and its toxins to quality of spelt wheat. The results showed that fungal contamination significantly reduced both trade and technological quality parameters. Volume weight, thousand kernel weight and wet gluten were significantly decreased, while protein content was significantly higher in Alternaria inoculated treatments. Although with slight decrease, falling number was not significantly affected by fungal contamination. The most negative impact of alternariol (AOH) was registered on volume weight and thousand kernel weight (-0.847; -0.898), while highly significant positive correlation was found between AOH and protein content (0.758). Alternaria spp. additionally destroyed spelt gluten structure, resulting in reduction of dough energy and baking quality with no significant influence of mycotoxins (AOH and AME) on technological quality parameters.

Isolation, identification and selection of antagonistic yeast against Alternaria alternata infection and tenuazonic acid production in wine grapes from Argentina

Epiphytic isolates with yeast characteristics from grapes of the Malbec cultivar were obtained in order to find antagonists against Alternaria alternata. From a total of 111 isolates, 82% corresponded to the yeast-like organism Aureobasidium pullulans and the rest to the non-Saccharomyces yeasts Hanseniaspora uvarum (6.3%), Metschnikowia pulcherrima or spp. (5.4%), Cryptoccocus laurentti II (2.7%), Starmerella bacilaris or Candida zemplinina (2.7%) and Rhodotorula spp. (0.9%). The 22.4% (15 out of 67) of epiphytic yeasts and yeast-like organisms evaluated were able to reduce A. alternata infection from 0.0 to 4.4% when applied 2h previous to pathogen inoculation on wounds of grape berries. From these selected strains, 14 out of 15 strains completely prevented A. alternata infection (0.0%), which implies potential for field application. All Metschnikowia (pulcherrima or spp.), S. bacillaris and almost all H. uvarum evaluated strains showed antagonist capability against A. alternata. Meanwhile, none of the lesser nutritional requirement strains belonging to A. pullulans, Cr. laurenti II and Rhodotorula spp. did. All the yeasts with capacity to prevent A. alternata infection also reduced tenuazonic acid (TA) production by 81.2 to 99.8%, finding TA levels similar to negative controls. Therefore, the epiphytic yeasts selected are promising as biological control agents against Alternaria infection and toxin production in grapes for winemaking.

Isolation and expression analysis of defensin gene and its promoter from Brassica juncea

The full-length pathogen-inducible plant defensin gene encoding 80 amino acid sequences of pathogen-related gene PR12 (Bjdefensin) was isolated from Brassica juncea. Conserved domain (CD) search reveals its similarity with gamma thionin and knottins families of plant antimicrobial peptides. The protein blast reveals more than 80% of its similarity with defensin-like protein of Brassica rapa and Camelina sativa. Gene expression studies revealed that the transcript levels of Bjdefensin gene increases significantly upon Alternaria infection, jasmonic acid and wounding treatments but was not induced by salicylic acid. To further study the stress-inducible regulation of Bjdefensin gene, its promoter (2.5 kb) was isolated and cloned upstream of GUS gene in pORER2 vector. In silico studies of Bjdefensin promoter showed many important conserved cis-elements, responsive to biotic and abiotic stresses. Histochemical GUS assay showed pathogen-inducible expression of Bjdefensin promoter after fungal infection. Bjdefensin promoter was also induced by Jasmonic acid and wounding.

Expression analysis of chitinase upon challenge inoculation to Alternaria wounding and defense inducers in Brassica juncea

Chitinases are the hydrolytic enzymes which belong to the pathogenesis-related (PR) protein family and play an important role not only in plant defense but also in various abiotic stresses. However, only a limited number of chitinase genes have been characterised in B. juncea. In this study, we have characterised B. juncea class IV chitinase gene (accession no EF586206) in response to fungal infection, salicylic acid (SA), jasmonic acid (JA) treatments and wounding. Gene expression studies revealed that the transcript levels of Bjchitinase (BjChp) gene increases significantly both in local and distal tissues after Alternaria infection. Bjchitinase gene was also induced by jasmonic acid and wounding but moderately by salicylic acid. A 2.5kb class IV chitinase promoter of this gene was isolated from B. juncea by Genome walking (accession no KF055403.1). In-silico analysis of this promoter revealed a number of conserved cis-regulatory elements related to defense, wounding and signalling molecules like SA, and JA. For validation, chitinase promoter was fused to the GUS gene, and the resultant construct was then introduced into Arabidopsis plants. Histochemical analysis of T2 transgenic Arabidopsis plants showed that higher GUS activity in leaves after fungal infection, wounding and JA treatment but weakly by SA. GUS activity was seen in meristematic tissues, young leaves, seeds and siliques. Finally investigation has led to the identification of a pathogen-inducible, developmentally regulated and organ-specific promoter. Present study revealed that Bjchitinase (BjChp) promoter is induced during biotic and environmental stress and it can be used in developing finely tuned transgenics.

The occurrence of Alternaria species on cabbage in Iran

In a study on Alternaria species, associated with cabbage black spot disease in Urmia, West Azerbaijan, Iran, cabbage fields were inspected during the growing seasons of 2012–2013 and leaves with suspected symptoms of Alternaria infection were collected. A total of 135 isolates with Alternaria characteristics were obtained from 10 main growing areas in this region and studied taxonomically. On the basis of morphological characteristics of the studied isolates, 8 species viz. Alternaria arbusti, A. brassicicola, A. destruens, A. infectoria, A. perangusta, A. tenuissima, A. turkisafria and A. vaccinii were identified. Alternaria tenuissima with 53 isolates, A. brassicicola with 38 isolates and A. destruens with 29 isolates had respectively the highest frequency among the identified species and distributed all over the studied area. A. arbusti and A. perangusta each with only one isolate had the lowest frequency. Results obtained from the pathogenicity tests showed that all the tested isolates from identified species were pathogenic on cabbage leaves, although there were statistically significant differences in virulence of the tested isolates. A. brassicicola isolates had the highest virulence and A. arbusti and A. vaccinii isolates had the lowest virulence. Isolates belonging to other species had moderate virulence. Except A. brassicicola which had been previously reported from cabbage in Iran, all other seven species are reported for the first time from cabbage as the causal agents of black spot disease. Also, A. arbusti, A. perangusta and A. vaccinii are reported as new species for Iran mycoflora.

PCR and real-time PCR assays to detect fungi of Alternaria alternata species.

Fungi of the Alternaria genus are mostly associated with allergic diseases. However, with a growing number of immunocompromised patients, these fungi, with A. alternata being the most prevalent one, are increasingly recognized as etiological agents of infections (phaeohyphomycoses) in humans. Nowadays, identification of Alternaria spp. requires their pure culture and is solely based on morphological criteria. Clinically, Alternaria infections may be indistinguishable from other fungal diseases. Therefore, a diagnostic result is often delayed or even not achieved at all. In this paper we present easy to perform and interpret PCR and real-time PCR assays enabling detection of A. alternata species. On the basis of alignment of β-tubulin gene sequences, A. alternata-specific primers were designed. DNA from fungal isolates, extracted in a two-step procedure, were used in PCR and real-time PCR assays followed by electrophoresis or melting temperature analysis, respectively. The assays specificity was confirmed, since positive results were obtained for all A. alternata isolates, and no positive results were obtained neither for other molds, dermatophytes, yeast-like fungi, nor human DNA. The assays developed here enable fast and unambiguous identification of A. alternata pathogens.

Ectopic Overexpression of Lectin in Transgenic Brassica juncea Plants Exhibit Resistance to Fungal Phytopathogen and Showed Alleviation to Salt and Drought Stress

Lectins are ubiquitous in nature and one of the most important secondary metabolites in plants. They are heterogeneous class of proteins that bind specifically and reversibly to carbohydrates and are used as a defence tool against various abiotic and biotic stresses. In this study, we describe generation of transgenic Brassica juncea plants over-expressing chickpea lectin in conferring fungal resistance. In addition, the transgenic plants also showed resistance against salinity (NaCl) and mannitol induced drought stress. The stable integration and transcript expression of the transgene was confirmed by southern blot and RT-PCR analysis in the transgenic plants. The transgenic lines were evaluated for resistance against Alternaria brassicae as assessed by the number and size of lesions and time taken for leaf necrosis, the Alternaria infection was delayed and restricted in the transgenic plants with the protection varying from 36-60% in different transgenic lines compared to the Untransformed Control (UC) plants. In addition, the transgenic Brassica juncea plants also showed tolerance against high salinity and drought stress. The Expression of lectin gene imparts greater water retention capacity, higher proline content and more chlorophyll retention with less membrane damage and reduction in electrolyte leakage in the transgenic plants compared to UC. Together, these findings suggest the potential use of chickpea lectin gene to engineer the crop plants for broad spectrum biotic and abiotic stress tolerance to improve crop productivity.

Jasmonic acid signalling mediates resistance of the wild tobacco Nicotiana attenuata to its native Fusarium, but not Alternaria, fungal pathogens.

We recently characterized a highly dynamic fungal disease outbreak in native populations of Nicotiana attenuata in the southwestern United States. Here, we explore how phytohormone signalling contributes to the observed disease dynamics. Single inoculation with three native Fusarium and Alternaria fungal pathogens, isolated from diseased plants growing in native populations, resulted in disease symptoms characteristic for each pathogen species. While Alternaria sp.-infected plants displayed fewer symptoms and recovered, Fusarium spp.-infected plants became chlorotic and frequently spontaneously wilted. Jasmonic acid (JA) and salicylic acid (SA) levels were differentially induced after Fusarium or Alternaria infection. Transgenic N. attenuata lines silenced in JA production or JA conjugation to isoleucine (JA-Ile), but not in JA perception, were highly susceptible to infection by F. brachygibbosum Utah 4, indicating that products derived from the JA-Ile biosynthetic pathway, but not their perception, is associated with increased Fusarium resistance. Infection assays using ov-nahG plants which were silenced in pathogen-induced SA accumulations revealed that SA may increase N. attenuata's resistance to Fusarium infection but not to Alternaria. Taken together, we propose that the dynamics of fungal disease symptoms among plants in native populations may be explained by a complex interplay of phytohormone responses to attack by multiple pathogens.