Category Archives: Wiley: Plant Pathology

Rapid detection of Fusarium fujikuroi in rice seeds and soaking water samples based on recombinase polymerase amplification‐lateral flow dipstick

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Rapid detection of Fusarium fujikuroi in rice seeds and soaking water samples based on recombinase polymerase amplification-lateral flow dipstick

The RPA-LFD technology can be used to detect Fusarium fujikuroi hidden in rice seeds, which is expected to become an early field monitoring tool for rice bakanae disease.


Abstract

Bakanae disease is a rice seedborne disease caused by the Fusarium (Gibberella) fujikuroi species complex (FFSC), among which F. fujikuroi is the dominant pathogen. Pathogens usually hide inside or on the surface of seeds, and infection occurs mainly at the germination stage. In this study, a method for the detection of F. fujikuroi in rice seeds and seed soaking water samples was established using recombinase polymerase amplification (RPA) technology with lateral flow device (LFD) chromatography test strips. A pair of specific primers and probes based on the cyp51c gene were screened. RPA-LFD was used to detect 10 F. fujikuroi strains, and the results showed that all of them tested positive and there was no cross-reaction with other Fusarium or non-Fusarium species. The target production of the RPA-LFD assay was obtained at 35–45°C for 8–14 min, and optimal reaction conditions of amplification at 39°C for 8 min is recommended. The sensitivity test showed that the detection limit of the RPA-LFD test for F. fujikuroi genomic DNA in rice seeds was 100 fg/μL, and the detection limit for F. fujikuroi spores in submerged water samples was 100 spores/mL. In the assay for field samples, it successfully detected F. fujikuroi carried in the seeds of three out of five rice varieties. In addition, the whole RPA-LFD assay can specifically detect F. fujikuroi within 30 min. This method is expected to become an early field monitoring tool for rice bakanae disease.

Intercropping and appropriate nitrogen application control faba bean Fusarium wilt by improving physiological and biochemical resistance and protein expression of faba bean

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Intercropping and appropriate nitrogen application control faba bean Fusarium wilt by improving physiological and biochemical resistance and protein expression of faba bean

Intercropping and nitrogen application control faba bean Fusarium wilt by improving the resistance of faba beans; energy metabolism-related, stress-related, and DNA repair proteins, and antioxidant enzymes were upregulated.


Abstract

This study set up four nitrogen application levels (0, 45, 90 and 135 kg/ha) and two planting systems (faba bean monocropping and faba bean and wheat intercropping) to investigate the incidence of faba bean Fusarium wilt under different treatments and determine the resistance enzyme activities and gene expression, protein expression, and other indexes of faba bean plants. At all N levels, faba bean and wheat intercropping controlled faba bean Fusarium wilt by decreasing the content of hydrogen peroxide and superoxide anion in faba bean roots, increasing the enzyme activity and gene expression of the superoxide dismutase and the gene expression of pathogenesis-related protein 1 (VfPR1), VfPR2, VfPR5 and VfPR10 disease resistance proteins in the roots, with the most significant effects at the N2 level (90 kg/ha). Further investigation of the impact of intercropping on faba bean roots using the N2 treatment showed that faba bean–wheat intercropping upregulated 288 proteins and downregulated 179 proteins compared with monocropping, and the functions of the upregulated proteins were mainly related to energy metabolism, antioxidant enzymes, stress and DNA repair. GO functional analysis showed that the upregulated proteins were mainly focused on the involvement in amide biological processes. KEGG enrichment analysis revealed that faba bean–wheat intercropping upregulated proteins involved in glutathione metabolism and ascorbic acid metabolism. In summary, at the N2 level, faba bean–wheat intercropping effectively mitigated root oxidative stress by enhancing antioxidant and disease resistance mechanisms in faba bean roots.

Ethylene production during Alternaria infections on potato plants and its antagonistic role in virulence of different Alternaria species

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Ethylene production during Alternaria infections on potato plants and its antagonistic role in virulence of different Alternaria species

Large-spored Alternaria species lose pathogenicity after treatment with the ethylene biosynthesis inhibitor 2-aminoethoxyvinyl glycine (AVG), while for small-spored species pathogenicity increased.


Abstract

Alternaria species are notorious pathogens of solanaceous crops and are known to produce a plethora of toxins. Nevertheless, the involvement of toxins or other virulence factors in Alternaria infections on potato plants has never been investigated. In view of this, we analysed whether different Alternaria species produced host- and non-host-specific toxins in vitro and in vivo. Secondly, we assessed if ethylene (ETH) is involved in potato plant infections, as was previously demonstrated in tomato. Although many toxins were detected in vitro, no toxins were present before symptom appearance in potato leaves. Isolates that made large conidia (A. solani) produced up to six times more ETH in vitro than isolates with small conidia (A. arborescens) in the presence of the ETH precursor α-keto-γ-methylthiobutyric acid (KMBA). In contrast, on potato leaf discs, an inverse relation was found between ETH emission and conidia size after correcting the data according to fungal DNA content, suggesting a role for ETH in symptom development rather than initiation. Moreover, application of a plant ETH biosynthesis inhibitor, 2-aminoethoxyvinyl glycine (AVG), resulted in a 60% reduction in necrosis after inoculation with a large-conidia isolate, whereas a 35% increase in necrosis was observed after inoculation with a small-conidia isolate. Finally, it was concluded that toxin production is not essential for symptom development of Alternaria on potato and that ETH (either from the plant and/or the fungus) is a crucial factor in symptom development by A. solani, whereas its role was found to be antagonistic for A. arborescens.

Geographic distribution, host preference and phylogenetic relationships among Pyricularia species inciting millet and rice blast disease in India

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Geographic distribution, host preference and phylogenetic relationships among Pyricularia species inciting millet and rice blast disease in India

The study explores the diversity, host preferences and phylogeny of Pyricularia strains found in rice and millets in India.


Abstract

Blast disease causes significant damage to millets (pearl millet, finger millet and foxtail millet) and rice in India. This study investigates strains of Pyricularia, the causal agent of blast disease, in rice and millets in India in terms of their diversity, host preferences and phylogeny. One hundred and thirty-six Pyricularia isolates causing rice and millet blast were collected from 46 locations in India. They displayed morphological diversity irrespective of host or location. All Pyricularia isolates were separated into two major clusters by a multilocus sequence-based phylogenetic tree, which also demonstrated that most isolates are grouped according to their host associations. In contrast, a few finger millet isolates were found to be grouped with foxtail millet isolates. We explored how Pyricularia isolates behaved when exposed to rice and millets. Finger millet isolates were shown to be pathogenic on a wide variety of millets, whereas rice isolates were only found to infect rice and wheat. The majority of the blast isolates of millets were shown to be pathogenic on common weed species of the millet ecosystem, such as Echinochloa crusgalli, Eleusina indica and Erogrotis gagantica. Our findings emphasize the importance of pathogen surveillance in both cultivated crops and weed hosts, as well as the possible risk of blast fungus infection in Indian millets due to host expansion. Blast disease control programmes in India will be greatly enhanced by the knowledge gained in this study on the diversity and host association of Pyricularia strains.

An emergent plant‐parasitic nematode in Brazil: Aphelenchoides besseyi. Current status and research perspectives

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An emergent plant-parasitic nematode in Brazil: Aphelenchoides besseyi. Current status and research perspectives

We review the biology, life cycle, host range and management solutions of an emergent pathogen in Brazil, all in the context of the landmark events leading to the rise of Aphelenchoides besseyi (Created using Biorender).


Abstract

Aphelenchoides besseyi is an emerging and yet overlooked plant parasite of many economically important crops, including cotton, soybean and common bean. It presents an economic risk to these crops in several countries, notably in Brazil. Although first reported infecting strawberries in the United States as early as 1942, it was only identified to be the causal agent of green stem and foliar retention (GSFR) disease in Brazil in 2017. Currently, there are no chemical nematicides registered in Brazil against A. besseyi, and no known sources of genetic resistance. Here, we review the biology of A. besseyi, its spread across Brazil, its relevance to the country's current and future agriculture and the limited control measures. We describe control measures that have been successfully used to manage infestations of other plant-parasitic nematodes and could potentially be extended to use in the control of A. besseyi. We also review and discuss potential future control measures, such as RNA interference and genome editing, for the development of crops with enhanced resistance to A. besseyi.

Sensitivity of dominant UK Phytophthora infestans genotypes to a range of fungicide active ingredients

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Sensitivity of dominant UK Phytophthora infestans genotypes to a range of fungicide active ingredients

Dominant UK Phytophthora infestans genotypes (EU6, EU36 and EU37) were tested for sensitivity to seven fungicide active ingredients (2019–22). EU37 isolates were insensitive to fluazinam; no insensitivity to other fungicides was found.


Abstract

Late blight, caused by Phytophthora infestans, is a serious disease of potatoes worldwide and is predominantly controlled by repeated prophylactic use of fungicides throughout the growing season. Effective blight management and integrated pest management strategies rely on knowledge of the efficacy of available fungicides to control contemporary genotypes of P. infestans. Between 2019 and 2022, representative isolates of the newer dominant genotypes EU36, EU37 and the older dominant genotype EU6 were sampled from GB crops and tested for sensitivity to seven commonly used fungicide active ingredients (cyazofamid, fluopicolide, mandipropamid, propamocarb, oxathiapiprolin, amisulbrom and mancozeb) used preventatively in detached leaf tests and zoospore motility assays where appropriate. Dose–response curves based on lesion area (mm2) were constructed, and EC50 values calculated. Isolates of P. infestans genotype EU37 were insensitive to fluazinam as previously reported. No insensitivity, or progression towards resistance over time, to any of the other fungicides was observed in any isolates of the genotypes tested, and EC50 values were generally in line with previous testing. Zoospore motility tests with fluopicolide revealed significantly higher MIC values for isolates of genotype EU36 compared with EU37 and EU6, which, whilst not indicative of resistance at the low concentrations of active ingredient tested, may be a factor contributing to the overall dominance of that genotype in the wider population of P. infestans. The evidence suggests that the fungicides tested, with the exception of fluazinam and EU37, are effective for the control of P. infestans genotypes dominant in the GB population up until 2022.

The coffee leaf rust pandemic: An ever‐present danger to coffee production

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The coffee leaf rust pandemic: An ever-present danger to coffee production

The history of the fungal disease coffee leaf rust is highlighted along with recent epidemics and future scenarios. Possible causes of these outbreaks are also examined.


Abstract

Coffee leaf rust (CLR) is caused by the biotrophic pathogenic fungus Hemileia vastatrix. Despite being the most researched coffee disease, mysteries still exist relating to its epidemiology and biology. The objective of this work is to highlight past and present events concerning this prominent coffee disease. We start with an historical overview of the homeland of Coffea arabica, the Afromontane forest of south-west Ethiopia, and then follow its journey across the globe linked to colonial trade and power struggles. We report the relevance of CLR to coffee production today, with a focus on the Americas and summarize unproven hypotheses in relation to the cause of recent epidemics. We present an original hypothesis concerning the first major outbreak occurring in 1869 in Ceylon (Sri Lanka), based on geopolitical connections to global trade. We review old and new options for management of the disease. The likelihood of a yet undetected alternate host of H. vastatrix is also considered as an additional piece of the epidemiological puzzle. Finally, we reflect on the interactions between H. vastatrix and a changing climate. By better understanding past events, linked to CLR, we may be better prepared for future outbreaks.

The length of the 3′ UTR of the tomato torrado virus (ToTV) RNA1 affects virus accumulation in Solanum lycopersicum during mechanical passages from plant to plant

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The length of the 3′ UTR of the tomato torrado virus (ToTV) RNA1 affects virus accumulation in Solanum lycopersicum during mechanical passages from plant to plant

ToTV-Kra defective genomes with truncated 3′ untranslated region of RNA1 are infectious. Changes in RNA1 length affect viral replication and sap transmission and may have arisen spontaneously or as an adaptation to the mode of viral transmission.


Abstract

Tomato torrado virus (ToTV), a member of the Torradovirus genus, primarily infects tomatoes. Previous analyses revealed high heterogeneity in the 3′ untranslated region (3′ UTR) of RNA1 of isolate ToTV-Kra. In addition to the full-length 3′ UTR RNA1 (a wild-type, wt), four truncated versions (var2, var3, var4 and var5) were identified. Here, we investigated the biological importance of this phenomenon by assessing whether such defective genomes are infectious individually, and how the length of the 3′ UTR influences disease symptoms, virus transmission and viral RNA accumulation. Using the ToTVpJL-Kra infectious clone, we introduced deletions corresponding to the known RNA1 defective variants and examined their impact on ToTV virulence and sap transmission ability. Viral RNA accumulation was assessed in agroinfiltrated tomatoes, as well as during serial passages. We found that all defective genomes were infectious and the length of the 3′ UTR of RNA1 influenced viral RNA accumulation. Tomatoes agroinfiltrated with var2, var3 or var5 showed the highest copy numbers of genomic RNAs. However, during serial passages, ToTVpJL-Kra-var1 and -var2 (six nucleotides shorter) showed limited sap transmission ability compared to the other variants, which persisted and replicated well in tomatoes. Plants treated with ToTVpJL-Kra-var3, -var4 and a mixture of var1–var5 showed the highest viral RNA accumulation, which was not associated with increased symptom severity in comparison to the other variants. Additionally, we identified a further sequence insertion in the 3′ UTR of var3 RNA1. This insertion could have occurred spontaneously or as a result of virus adaptation to the mode of transmission.

Comparative omics analysis for novel target discovery in plant pathogens: A case study for Magnaporthe oryzae

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Comparative omics analysis for novel target discovery in plant pathogens: A case study for Magnaporthe oryzae

A novel strategy, integrating omics and bioinformatics, identifies distinct fungal pathways, revealing a promising target for precision fungicides against Magnaporthe oryzae, causing rice blast disease.


Abstract

The central concern surrounding chemical pesticide application is its potential adverse effects on non-target organisms. For fungal pathogens, the search for specific targets has been complicated by the similarities in pathways shared between these pathogens and humans. We present a comprehensive strategy, integrating comparative omics and bioinformatics, to pinpoint precise targets for fungicides effective against the fungal pathogen Magnaporthe oryzae, responsible for rice blast disease. Our approach involves subtractive metabolic pathways, homology screening and target prioritization. Through subtractive metabolic analysis, we identified three unique M. oryzae pathways, distinct from human and rice. Nonredundant protein sequences were subsequently subjected to BLASTP screening against human and rice, as well as other databases from diverse organisms. Target subcellular localization was predicted using eight tools, including artificial intelligence and a deep-learning method. A comprehensive examination of biological processes was conducted, including gene expression, protein–protein interactions, network enrichment, broad-spectrum activity and physicochemical analysis. Glutamate 5-kinase emerged as the prime candidate for targeted fungicide development, promising progress in precision-oriented solutions.