Alternaria Mali Research Articles

Integrated Control of Alternaria Blotch in Apple Orchards

ABSTRACTAn investigation of Alternaria blotch in apple orchards was conducted to evaluate the effectiveness of fungicides, plant extracts and bioagents against Alternaria mali through the development of integrated disease management strategies. Under pot conditions, potential combinations of fungicides, plant extracts and biocontrol agents for mitigating the disease were evaluated. Furthermore, polyhouse studies showed that bioagents such as Trichoderma viride, Bacillus subtilis and Pseudomonas fluorescens have disease control potential. Moreover, this research explored the impact of fungicides on the production of primary inoculum, highlighting the potential to impede conidial production by the pathogen. Over two cropping seasons, field assessments indicated the efficiency of integrated approaches in managing Alternaria blotch of apples. This study highlights the importance of reducing chemical inputs while ensuring successful disease management, offering important insights into a more sustainable approach to the management of diseases in apple orchards.

Characterization of Alternaria blotch disease of apple in Himachal Pradesh, India: insights on morphology, pathogenicity, and molecular features.

Alternaria blotch disease in Himachal Pradesh, India, caused by Alternaria spp., adversely affects apple cultivars, resulting in reduced fruit size and quality accompanied by premature leaf fall. Sixteen Alternaria isolates from apple growing regions underwent comprehensive analysis including morphology, pathogenicity, and molecular characterization. Variations in conidiophore and conidia dimensions, shapes, and divisions were observed among isolates. Pathogenicity assays revealed differences in incubation periods, latent phases, and disease responses. Molecular characterization via nuclear ITS rDNA and RAPD analysis indicated 99-100% homology with Alternaria alternata, Alternaria mali, and other Alternaria spp., with a close phylogenetic relationship to Chinese isolates. Differentiation of isolates based on origin, cultural characteristics, and morphology was achieved using RAPD markers. The study identifies diverse genotypes and morphotypes of Alternaria contributing to apple blotch disease in Himachal Pradesh. These findings highlight the complexity of the pathogenic environment and hold significant implications for disease management in apple orchards.

Pathogenic Factors and Mechanisms of the Alternaria Leaf Spot Pathogen in Apple

Alternaria leaf spot seriously threatens the sustainable development of the global apple industry, causing significant losses and reducing fruit quality and yield. The causal agent Alternaria alternata f. sp. mali (Alternaria mali, ALT) produces various molecules to modulate infection, such as cell wall-degrading enzymes, toxins, and elicitor-like molecules. ALT produces the host-specific AM-toxin, an important pathogenicity factor. ALT also releases effectors into apple cells that modify host defense, but these proteins have not yet been described. Here, we identified the pathogenic fungal types responsible for early defoliation from diseased leaves of Fuji (Malus domestica cv. ‘Fuji’) apple collected from five districts in Shandong Province, China. The ALT isolates ALT2 to ALT7 were pathogenic to four apple cultivars, with ALT7 being the most aggressive. We extracted mycotoxins (AM-toxin-2 to AM-toxin-7) from each isolate and used them to treat different apple varieties, which led to leaf-spot symptoms and damaged chloroplasts and nuclear membranes, followed by cell death. AM-toxin-7 produced the most severe symptoms, but chloroplasts remained intact when the mycotoxin was inactivated. Mass spectrometry identified 134 secretory proteins in ALT7 exosomes, and three secreted proteins (AltABC, AltAO, and AltPDE) were confirmed to be involved in apple pathogenesis. Therefore, ALT secretes AM-toxin and secretory proteins as an infection strategy to promote fungal invasion and overcome the host defense system.

Determination of suppression efficiency of vermicompost extracts on some aerial fungal plant pathogens

The use of vermicompost in agriculture has become increasingly common, especially in organic agriculture. In this research, the suppression efficiency of horse and cattle vermicompost extracts against some aerial fungal plant pathogens (Monilinia laxa, Cytospora leucostoma, Botryosphaeria obtusa, Phomopsis viticola, Alternaria mali, and Botrytis cinerea) that damage fruit trees and are common in fruit production areas, was studied for the first time in our country. 25%, 50%, 75%, and 100% concentrations of horse and cattle extracts were tested against fungal plant isolates. The results were evaluated by two-way ANOVA testing the suppression rates of vermicompost extracts in petri plates. While the best results were found in M. laxa (90.6%), P. viticola (80.2%), A. mali (65.1%) at 100% concentration for horse and cattle vermicomposts respectively, the suppression of B. obtusa (44.7%), C. leucostoma (38.1%), and B. cinerea (35.5%) was found to be lower.

Coinfection of Two Mycoviruses Confers Hypovirulence and Reduces the Production of Mycotoxin Alternariol in Alternaria alternata f. sp. mali

Alternaria leaf blotch caused by Alternaria alternata apple pathotype (Alternaria mali) is an important fungal disease that affects the production of apples worldwide. Mycoviruses harbored in plant pathogenic fungi can confer hypovirulence in their hosts and have attracted widespread attention as potential biocontrol tools. In this study, the coinfection of two mycoviruses, named A. alternata chrysovirus 1 strain QY2 (AaCV1-QY2) and A. alternata magoulivirus 1 (AaMV1), respectively, were isolated from A. alternata f. sp. mali strain QY21. Sequence analyses revealed that AaCV1-QY2 virus belonged to the genus Betachrysovirus and AaMV1 virus belonged to the genus Magoulvirus. These two mycoviruses were found to be associated with hypovirulence in A. alternata, among which AaCV1-QY2 might play a relatively leading role. Because the elimination of AaMV1 from the strain QY21 does not affect the hypovirulence trait, which indicates that the virus AaCV1-QY2 can independently induce slow growth and reduce host virulence. Moreover, the presence of viruses decreased the accumulation of the mycotoxin alternariol (AOH) in A. alternata strains. Intriguingly, AaCV1-QY2/AaMV1 mycoviruses can be horizontally transmitted to other A. alternata strains, and this coinfection can promote the interspecific transmission efficiency of AaCV1-QY2. To our knowledge, this study reports the first description of the member of Chrysovirus is related to hypovirulence in Alternaria spp. that facilitates the development of biocontrol measures of A. mali Roberts.

Tennessenoid A, an Unprecedented Steroid−Sorbicillinoid Adduct From the Marine-Derived Endophyte of Aspergillus sp. Strain 1022LEF

Marine natural products, characterized by fascinating drug-like functionalities and promising biological activities, are important base materials for innovative drugs and agrochemicals. Chemical investigations of the marine-algal-derived endophytic fungus Aspergillus sp. 1022LEF residing in the inner tissue of marine red alga yielded a novel polyketide-terpene hybrid metabolite, namely tennessenoid A (1), as well as six known biosynthetic congeners including two steroids, ergosta-4,6,8(14),22-tetraen-3-one (2) and (22E,24R)-3α-ureido-ergosta-4,6,8(14),22-tetraene (3), and four sorbicillinoid-based compounds, saturnispol G (4), trichodimerol (5), and dihydrotrichodimer ethers A and B (6 and 7). Their structures were unambiguously determined based on extensive 1D/2D NMR and HRESIMS spectroscopic analyses. Tennessenoid A (1) was characterized as an unprecedented steroid−sorbicillinoid adduct via a C−C bond, which was rarely-observed in natural products. All of the isolated compounds were evaluated for their antifungal activities against eight plant pathogenetic fungi. 1, in particular, demonstrated broad-spectrum activities against Sclerotium rolfsii Sacc., Fusarium oxysporum (Schl.) F.sp cucumerinum Owen, Coniella diplodiella Petrak et Sydow, Physalospora piricola Nose., Fusarium graminearum schw., Alternaria mali rob., Colletotrichum orbiculare Arx., and Alternaria porri (E11iott) Cifed., with the inhibition zone diameters ranging from 2 to 7 mm.

Control of Apple Fruit Rot Caused by Alternaria porri and Alternaria mali by Using Hot Water Treatment and Some Inorganic Salts

Apple rot is one of the most important apple diseases worldwide. The disease causes significant losses in both the quantity and quality of apple fruits. In this study, the antifungal activity of hot water treatment and salts were investigated against apple fruit rots caused by Alternaria porri and Alternaria mali. Linear growth of tested fungi was inhibited at 5ºC, however, growth was increased by increasing storage temperature degree from 15ºC to 25ºC and decreased at 35ºC. On the other hand, hot water treatment at 55ºC significantly reduced the decay index and severity of infection. When salts such as potassium bicarbonate (KCO3), calcium chloride (CaCl2), sodium bicarbonate (NaHCO3) and ammonium bicarbonate (NH4CO3) was applied, a significant reduction in linear growth and fruit rot incidence was noticed using potassium bicarbonate. Calcium chloride, ammonium bicarbonate and sodium bicarbonate greatly inhibited growth of A. porri and A. mali. The most effective inhibitor of fruit decay was potassium bicarbonate and calcium chloride.

Alternaria mali (leaf spot: apple)

Alternaria mali (leaf spot: apple)

Design, Synthesis, Antimicrobial Evaluation, and Molecular Modeling Studies of Novel Indolinedione−Coumarin Molecular Hybrids

Keeping in view various pharmacological of indole and coumarin derivatives, a new series of indolindione−coumarin molecular hybrids was rationally designed and synthesized. All synthesized hybrid molecules were evaluated for their antimicrobial potential against Gram negative bacterial strains (Escherichia coli and Salmonella enterica), Gram-positive bacterial strains (Staphylococcus aureus and Mycobacterium smegmatis), and four fungal strains (Candida albicans, Alternaria mali, Penicillium sp., and Fusarium oxysporum) by using the agar gel diffusion method. Among all synthetics, compounds K-1 and K-2 were found to be the best antimicrobial agents with the minimum inhibitory concentration values of 30 and 312 μg/mL, against Penicillium sp. and S. aureus, respectively. The biological data revealed some interesting facts about the structure−activity relationship which state that the electronic environment on the indolinedione moiety and carbon chain length between indolinedione and triazole moieties considerably affect the antimicrobial potential of the synthesized hybrids. Various types of binding interactions of K-2 within the active site of S. aureus dihydrofolate reductase were also streamlined by molecular modeling studies, which revealed the possible mechanism for potent antibacterial activity of the compound.

Bio-efficacy evaluation of Chlorothalonil 40% w/w + Difenoconfazole 4% w/w SC against apple diseases

Uttarakhand hills are best suited for production of a variety of fruit crops due to favorable agro-climatic conditions with apple being the most important temperate fruit grown in the region. Apple is the prime fruit of Uttarakhand and plays a major role in horticultural development and in improving economic status of the growers. The major diseases of apple crop in hill and mountain regions are scab [Venturia inaequalis (Cke.) Wint], premature leaf fall (Marssonina coronaria and Alternaria mali) and powdery mildew [Podosphaera leucotricha (Ellis and Everhart)] etc. These diseases have already plagued apple cultivation in Uttarakhand hills which happen to be the 3rd largest apple growing state of the country. Hence, to manage these diseases, Chlorothalonil 40% w/w + Difenoconazole 4% w/w SC at different dosages along with standard checks viz., Chlorothalonil 75% WP, Difenoconazole 25% EC, Propineb 70% WP, Sulphur 80 WG and Metiram 55% + Pyraclostrobin 5% WG at recommended doses were evaluated for bio-efficacy and phytotoxicity against apple scab, premature leaf fall and powdery mildew diseases at Harsil (District- Uttarkashi, Uttarakhand) during 2017 and 2018. The data analysis of two crop seasons (2017 & 2018) showed that all the treatments differed significantly with respect to per cent disease severity and per cent disease reduction over control for all the diseases studied. However, the treatment T4 (Chlorothalonil 40% + Difenoconazle 4% w/w SC @ 900 ml/ha) was found most effective followed by treatment T3 (Chlorothalonil 40% + Difenoconazole 4% w/w SC @ 800ml/ha) for all the diseases studied under present materials and conditions at Harshil location during 2017 and 2018. The data of two crop seasons indicated that maximum yield (98.83q/ha in 2017 and 95.20 q/ha in 2018) was recorded when the crop was sprayed with Chlorothalonil 40% + Difenoconazle 4% w/w SC @ 900 ml/ha followed by Chlorothalonil 40% + Difenoconazole 4% w/w SC @ 800ml/ha with 95.44 q/ha in 2017 and 94.55q/ha in 2018, respectively. For phytotoxicity studies, Chlorothalonil 40% + Difenoconazle 4% w/w SC @ 900 & 1800 ml/ha did not show any phytotoxic effects viz., yellowing, necrosis, chlorosis, epinasty, hyponasty and stunting on apple crop.

First Report of Leaf Blight Caused by Alternaria mali and A. arborescens on Date Palm (Phoenix dactylifera) in Tunisia

First Report of Leaf Blight Caused by <i>Alternaria mali</i> and <i>A. arborescens</i> on Date Palm (<i>Phoenix dactylifera</i>) in Tunisia

Fusaricidin Produced by Paenibacillus polymyxa WLY78 Induces Systemic Resistance against Fusarium Wilt of Cucumber.

Cucumber is an important vegetable crop in China. Fusarium wilt is a soil-borne disease that can significantly reduce cucumber yields. Paenibacillus polymyxa WLY78 can strongly inhibit Fusarium oxysporum f. sp. Cucumerium, which causes Fusarium wilt disease. In this study, we screened the genome of WLY78 and found eight potential antibiotic biosynthesis gene clusters. Mutation analysis showed that among the eight clusters, the fusaricidin synthesis (fus) gene cluster is involved in inhibiting the Fusarium genus, Verticillium albo-atrum, Monilia persoon, Alternaria mali, Botrytis cinereal, and Aspergillus niger. Further mutation analysis revealed that with the exception of fusTE, the seven genes fusG, fusF, fusE, fusD, fusC, fusB, and fusA within the fus cluster were all involved in inhibiting fungi. This is the first time that demonstrated that fusTE was not essential. We first report the inhibitory mode of fusaricidin to inhibit spore germination and disrupt hyphal membranes. A biocontrol assay demonstrated that fusaricidin played a major role in controlling Fusarium wilt disease. Additionally, qRT-PCR demonstrated that fusaricidin could induce systemic resistance via salicylic acid (SA) signal against Fusarium wilt of cucumber. WLY78 is the first reported strain to both produce fusaricidin and fix nitrogen. Therefore, our results demonstrate that WLY78 will have great potential as a biocontrol agent in agriculture.

Design, Synthesis, Antimicrobial Evaluation, and Molecular Modeling Studies of Novel Indolinedione-Coumarin Molecular Hybrids.

Keeping in view various pharmacological attributes of indole and coumarin derivatives, a new series of indolindione–coumarin molecular hybrids was rationally designed and synthesized. All synthesized hybrid molecules were evaluated for their antimicrobial potential against Gram-negative bacterial strains (Escherichia coli and Salmonella enterica), Gram-positive bacterial strains (Staphylococcus aureus and Mycobacterium smegmatis), and four fungal strains (Candida albicans, Alternaria mali, Penicillium sp., and Fusarium oxysporum) by using the agar gel diffusion method. Among all synthetics, compounds K-1 and K-2 were found to be the best antimicrobial agents with the minimum inhibitory concentration values of 30 and 312 μg/mL, against Penicillium sp. and S. aureus, respectively. The biological data revealed some interesting facts about the structure–activity relationship which state that the electronic environment on the indolinedione moiety and carbon chain length between indolinedione and triazole moieties considerably affect the antimicrobial potential of the synthesized hybrids. Various types of binding interactions of K-2 within the active site of S. aureus dihydrofolate reductase were also streamlined by molecular modeling studies, which revealed the possible mechanism for potent antibacterial activity of the compound.

Structure and Anti-Tumor Activities of Exopolysaccharides from Alternaria mali Roberts.

In this study, an extracellular polysaccharide from Alternaria mali Roberts (AMEP) was extracted, and its structure was characterized, in addition to its antitumor activity in vitro. Neutral polysaccharide AMEP-1 and anionic polysaccharide AMEP-2 were isolated from AMEP, and their monosaccharide compositions consisted of mannose (Man), glucose (Glc), and galactose (Gal) but at different ratios. The linking mode of both AMEP-1 and AMEP-2 is Manp-(1→4) and Glcp-(1→6), and the branched chains are connected to the main chain through O-6. AMEP-2 inhibited the proliferation of BGC-823 cells in a time- and concentration-dependent manner. AMEP-2 also induced the apoptosis of BGC-823 cells, and showed anti-tumor effects by inducing cell cycle arrest in the S phase, reactive oxygen species production, and mitochondrial membrane potential reduction in BGC-823 cells. Therefore, AMEP-2 shows potential for further development as a novel anti-tumor agent.

Relationship between foliar endophytes and apple cultivar disease resistance in an organic orchard

Many studies have shown that foliar endophytes enhance host resistance to leaf pathogens. Although plants show large genotype-related intraspecific variation in pathogen resistance, few studies have examined whether disease resistance is also influenced by the endophyte community. In the present study, we tested the hypothesis that apple cultivar differences in leaf pathogen resistance are related to their respective foliar endophyte communities. We inoculated spores of Alternaria leaf spot (Alternaria mali) in an organic orchard that had not been exposed to any chemical pesticide for over 30 years, and evaluated leaf damage in 18 apple trees belonging to three cultivars with differing levels of resistance. The richness, composition, and abundance of the foliar endophyte communities in the same 18 trees were also examined using terminal restriction fragment length polymorphism. We found that cultivar resistance to lower leaf damage correlated significantly with the abundance of endophytic fungal species. These results suggest that endophytic fungi can promote leaf spot resistance in apple cultivars.

The influence of microfilamentous fungi on wooden organ pipes: One year investigation

Wooden pipe organs are precious objects of cultural heritage the degradation of which has been very poorly studied. Fungal strains recovered from an organ dating back to the 19th century included Alternaria mali, Eurotium cristatum, Aspergillus amstelodami, Penicillium crustosum and Aspergillus sydowii. These isolates were used to artificially contaminate wooden pipes treated with linseed oil varnish and varnish-free. The pipes were incubated at different temperatures and relative humidity for one year. The pipes, incubated at a high relative humidity (70–75%), collapsed due to the biodegradation of glued joints. After one year, inoculated strains (Alternaria mali, Penicillium crustosum and Aspergillus sydowii) as well as some non-inoculated Talaromyces rugulosus, Paecilomyces formosus, Cladosporium cladosporioides, Aspergillus versicolor and Epicoccum nigrum were recovered from the pipes. Few strains exhibited lignolytic activity, while almost all were able to hydrolyze the rabbit glue used to join the wood elements of the pipes. A newly developed portable pipe-sound controller did not detect differences of sound spectra between the uncontaminated and the few surviving contaminated pipes. In this study we have demonstrated that glue degradation was critical for pipe preservation and it can be tremendously accelerated above a certain relative humidity threshold. Therefore, it is important to apply a monitoring strategy able to check the environmental conditions, microbial contamination and pipe sound alteration in order to preserve these valuable and rare cultural heritage objects.

Study of bio-fabrication of iron nanoparticles and their fungicidal property against phytopathogens of apple orchards.

Current research trends on iron nanoparticles (FeNPs) are extensively focused because of their unique magnetic and electrical properties mostly applicable in essential medical devices. However, their fungicidal property against plant pathogens is very less known until date. Present study demonstrates a green technique for blending of FeNPs by utilising aqueous extract of neem leaf (Azadirachta indica A. Juss.) as reducing agent. Various characterisation techniques such as ultraviolet (UV)-visible spectroscopy, Fourier transform infrared spectroscopy transmission electron microscopy, scanning electron microscopy and X-ray diffraction were performed for FeNPs. The authors' results demonstrate the more cluster formation of FeNPs with size distribution of 20-80 nm. The bio-fabricated FeNPs showed enhanced biocidal activity against economically important phytopathogens of apple such as Alternaria mali, Botryosphaeria dothidea and Diplodia seriata. From the obtained results, it can be suggested that further delve into green synthesis of FeNPs can address future biotechnology concerns to limit the synthesis of FeNPs by conventional methods. Furthermore, the field study on pathogenic fungi can be an effective step to verify their agricultural applications.

Microwave-assisted Synthesis and antifungal activity of coumarin[8,7-e][1,3]oxazine derivatives.

The synthesis of novel coumarin[8,7-e][1,3]oxazine derivatives through a microwave-assisted three-component one-pot Mannich reaction is described in this study. All the target compounds were evaluated in vitro for their antifungal activity against Botrytis cinerea, Colletotrichum capsici, Alternaria solani, Gibberella zeae, Rhizoctonia solani, and Alternaria mali. The preliminary bioassays showed that 5e, 5m, and 5s exhibited good antifungal activity and the most active compound was 5m with an [Formula: see text] value as low as 2.1 nM against Botrytis cinerea.

Arabidopsis Plants Overexpressing the MsDREB2C Exhibit Increased Susceptibility to Alternaria mali Infection

Dehydration responsive element binding (DREBs) play a critical role in improving the stress tolerance of plants by interacting with a DRE/CRT cis-element present in the promoter region of various abiotic stress-responsive genes. In this study, a DREB2 homologous gene from Malus sieversii Roem., designated MsDREB2C (GenBank accession No. JQ790526), was isolated and characterized. MsDREB2C was localized to the nucleus of Arabidopsis protoplasts. qRT-PCR analysis demonstrated that MsDREB2C was induced by salicylic acid (SA) and jasmonic acid (JA). Furthermore, transgenic Arabidopsis plants overexpressing MsDREB2C exhibited increased sensitivity to Alternaria mali infection, and the constitutive expression of MsDREB2C in transgenic plants repressed the expression of PR genes and the activity of peroxidase under normal and pathogenic conditions. We then functionally characterized the MsDREB2C promoter region. Deletion analysis identified the regulatory regions responsible for the gene’s response to SA (−335 to −148 bp) and JA (−831 to −680 bp and −335 to −148 bp). These results suggested that overexpression of MsDREB2C decreased resistance to A. mali.

Bioactivity, toxicity and dissipation of hexaconazole enantiomers

In this study, the bioactivity, acute toxicity and dissipation in vegetables of the individual enantiomers of the fungicide hexaconazole had been investigated. The optical pure single enantiomers were prepared and the bioactivity of (+)-, (−)- and rac-hexaconazole was tested using four target fungi including Colletotrichum gloeosporioides Penz, Alternaria solani, Alternaria mali Roberts and Monilinia fructicola. The results showed (−)-hexaconazole was always more active than (+)-hexaconazole with the fungicidal activity 11–13-fold higher to A. solani, A. mali Roberts and Monilinia fructicola, and 1.26-fold higher to C. gloeosporioides Penz. (−)-Hexaconazole also showed 1.3-fold higher acute toxicity to aquatic species Daphnia magna based on the 48h EC50 values. There was obvious enantioselectivity in the dissipation in tomato with (−)-hexaconazole degraded faster resulting an enrichment of (+)-form, and the half-lives of (−)-hexaconazole and (+)-hexaconazole in tomato were 2.96d and 3.38d respectively, while it was not enantioselective in green pepper, in which the both enantiomers had the half-lives about 4.36d. The findings are helpful for better environmental and ecological risk assessment of hexaconazole on an enantiomeric level.