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10. Transcriptomics reveal the genetic coordination of early defense to Armillaria root rot (ARR) in Prunus spp.

Author

Lichun Cai, Adelberg, Jeffrey, Naylor-Adelberg, Jacqueline, Schnabel, Guido, Calle, Alejandro, Zhigang Li, Reighard, Gregory, Gasic, Ksenija, and Saski, Christopher A.

Subjects
ROOT rots, PRUNUS, OXIDOREDUCTASES, CHITIN, GLUTATHIONE transferase, TRANSCRIPTION factors, GENE expression, ROOTSTOCKS
Abstract

Armillaria root rot (ARR) poses a significant threat to the long-term productivity of stone-fruit and nut crops in the predominant production area of the United States. To mitigate this issue, the development of ARR-resistant and horticulturally-acceptable rootstocks is a crucial step towards the maintenance of production sustainability. To date, genetic resistance to ARR has been found in exotic plum germplasm and a peach/plum hybrid rootstock, 'MP-29'. However, the widely-used peach rootstock Guardian® is susceptible to the pathogen. To understand the molecular defense mechanisms involved in ARR resistance in Prunus rootstocks, transcriptomic analyses of one susceptible and two resistant Prunus spp. were performed using two causal agents of ARR, including Armillaria mellea and Desarmillaria tabescens. The results of in vitro co-culture experiments revealed that the two resistant genotypes showed different temporal response dynamics and fungus-specific responses, as seen in the genetic response. Gene expression analysis over time indicated an enrichment of defense-related ontologies, including glucosyltransferase activity, monooxygenase activity, glutathione transferase activity, and peroxidase activity. Differential gene expression and co-expression network analysis highlighted key hub genes involved in the sensing and enzymatic degradation of chitin, GSTs, oxidoreductases, transcription factors, and biochemical pathways likely involved in Armillaria resistance. These data provide valuable resources for the improvement of ARR resistance in Prunus rootstocks through breeding. [ABSTRACT FROM AUTHOR]

Published
2023
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11. The velvet family proteins mediate low resistance to isoprothiolane in Magnaporthe oryzae.

Author

Meng, Fan-Zhu, Wang, Zuo-Qian, Luo, Mei, Wei, Wen-Kai, Yin, Liang-Fen, Yin, Wei-Xiao, Schnabel, Guido, and Luo, Chao-Xi

Subjects
PYRICULARIA oryzae, SECONDARY metabolism, WHOLE genome sequencing, RICE blast disease, GENETIC transformation, VELVET, TRANSCRIPTION factors
Abstract

Isoprothiolane (IPT) resistance has emerged in Magnaporthe oryzae, due to the long-term usage of IPT to control rice blast in China, yet the mechanisms of the resistance remain largely unknown. Through IPT adaptation on PDA medium, we obtained a variety of IPT-resistant mutants. Based on their EC50 values to IPT, the resistant mutants were mainly divided into three distinct categories, i.e., low resistance (LR, 6.5 ≤ EC50 < 13.0 μg/mL), moderate resistance 1 (MR-1, 13.0 ≤ EC50 < 25.0 μg/mL), and moderate resistance 2 (MR-2, 25.0 ≤ EC50 < 35.0 μg/mL). Molecular analysis of MoIRR (Magnaporthe oryzae isoprothiolane resistance related) gene demonstrated that it was associated only with the moderate resistance in MR-2 mutants, indicating that other mechanisms were associated with resistance in LR and MR-1 mutants. In this study, we mainly focused on the characterization of low resistance to IPT in M. oryzae. Mycelial growth and conidial germination were significantly reduced, indicating fitness penalties in LR mutants. Based on the differences of whole genome sequences between parental isolate and LR mutants, we identified a conserved MoVelB gene, encoding the velvet family transcription factor, and genetic transformation of wild type isolate verified that MoVelB gene was associated with the low resistance. Based on molecular analysis, we further demonstrated that the velvet family proteins VelB and VeA were indispensable for IPT toxicity and the deformation of the VelB-VeA-LaeA complex played a vital role for the low IPT-resistance in M. oryzae, most likely through the down-regulation of the secondary metabolism-related genes or CYP450 genes to reduce the toxicity of IPT. Author summary: Isoprothiolane (IPT) resistance has emerged in Magnaporthe oryzae, due to the long-term usage of IPT to control rice blast in China, yet the mechanisms of the resistance remain largely unknown. Here, we explored the mechanisms of low IPT resistance in M. oryzae. Combining the whole genome sequencing and genetic transformation, we identified a conserved MoVelB gene, encoding the velvet family transcription factor to be a determinant for IPT toxicity. We further demonstrated that the deformation of the VelB-VeA-LaeA complex conferred the low IPT-resistance in M. oryzae, most likely through down-regulating the secondary metabolism-related genes or CYP450 genes to reduce the toxicity of IPT. This study improved our understanding of the resistance mechanism as well as the mode of action of IPT which will be helpful for making suitable strategies to manage the emerging resistance of IPT in M. oryzae. [ABSTRACT FROM AUTHOR]

Published
2023
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12. First Report of Rose Bent Neck Caused by Sclerotinia sclerotiorum on Commercial Cut Roses (Rosa hybrida L.).

Author

Muñoz, Melissa, Behnke, Logan E., Faust, James E., and Schnabel, Guido

Subjects
SCLEROTINIA sclerotiorum, ROSES, NECK, BOTRYTIS cinerea, SCLEROTIUM (Mycelium)
Abstract

Cut roses are highly valuable ornamentals and their profitability depends on the flower postharvest performance. Bent neck symptoms in roses make them unmarketable and are typically related to physiological disorders, bacteria accumulation in the vase solution, and Botrytis cinerea infection. Unusual bent neck symptoms were observed in 4.7% of 'Orange Crush' roses from two commercial shipments, resulting in complete flower collapse. This research was aimed to determine the causal agent of the bent neck symptoms. Following incubation in a humid chamber, symptomatic roses evolved in water-soaked lesions with the presence of white mycelium and sclerotia development. Fungal isolations and molecular characterization were performed and Sclerotinia sclerotiorum was identified as the causal agent of rose bent neck. Therefore, when bent neck symptoms are observed, S. sclerotiorum incidence should be considered to avoid possible outbreaks. [ABSTRACT FROM AUTHOR]

Published
2023
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38. Proposal for a unified nomenclature for target site mutations associated with resistance to fungicides

Author

Mair, Wesley, Lopz-Ruiz, Francisco, Stammler, Gerd, Clark, William, Burnett, Fiona, Hollomon, Derek, Ishii, Hideo, Thind, Tarlochan S., Brown, James KM, Fraaije, Bart, Cools, Hans, Shaw, Michael, Fillinger, Sabine, Walker, Anne-Sophie, Mellado, Emilia, Schnabel, Guido, Mehl, Andreas, and Oliver, Richard P.

Abstract

Evolved resistance to fungicides is a major problem limiting our ability to control agricultural, medical and veterinary pathogens and is frequently associated with substitutions in the amino acid sequence of the target protein. The convention for describing amino-acid substitutions is to cite the wild type amino acid, the codon number and the new amino acid, using the one letter amino acid code. It has frequently been observed that orthologous amino acid mutations have been selected in different species by fungicides from the same mode of action class, but the amino acids have different numbers. These differences in numbering arise from the different lengths of the proteins in each species. The purpose of the current paper is to propose a system for unifying the labelling of amino acids in fungicide target proteins. To do this we have produced alignments between fungicide target proteins of relevant species fitted to a well-studied “archetype” species. Orthologous amino acids in all species are then assigned numerical “labels” based on the position of the amino acid in the archetype protein.

Published
2016

39. Function of the genetic element ‘Mona’ associated with fungicide resistance in Monilinia fructicola

Author

Chen, Shuning, Yuan, Nannan, Schnabel, Guido, and Luo, Chaoxi

Subjects
Gene Knockout Techniques, Transformation, Genetic, Ascomycota, Mycelium, Drug Resistance, Fungal, Gene Expression Regulation, Fungal, Genes, Fungal, DNA Transposable Elements, Original Articles, DNA Methylation, Spores, Fungal, Promoter Regions, Genetic, Fungicides, Industrial
Abstract

The genetic element ‘Mona’ has been shown previously to be associated with resistance to demethylation inhibitors (DMIs) in Monilinia fructicola. In this study, the promoter activity of the ‘Mona’ element was demonstrated genetically and the activity was narrowed down to a 20‐bp active region through a series of deletions. ‘Mona’ knockout transformants (ΔMona) were generated from DMI‐resistant isolate Bmpc7, and EC(50) values and expression of the MfCYP51 gene were found to be reduced in transformants compared with the parental isolate. When the ‘Mona’ element was inserted into the upstream region of the MfCYP51 gene of the DMI‐sensitive isolate HG3, the EC(50) values and expression of the MfCYP51 gene increased in the transformants compared with the parental sensitive isolate. These results indicate that the ‘Mona’ element determines the DMI fungicide resistance through the up‐regulation of the expression of the downstream MfCYP51 gene. No fitness penalty was observed in knockout and insertion transformants, i.e. transformants showed similar mycelial growth rate, sporulation and ability to cause lesions on fruit compared with their parental isolates, suggesting that the ‘Mona’ element does not affect basal life activities.

Published
2016

40. 2016 Southeast Regional Caneberry Integrated Management Guide. Southeastern Small Fruit Consortium

Author

Brannen, Philip, Schnabel, Guido, Burrack, Hannah J., Bessin, Richard, Pfeiffer, Douglas G., Mitchem, Wayne, Jennings, Katie, Lockwood, David, Fernandez, Gina, Sial, Ash, Virginia Cooperative Extension (VCE), and Entomology

Abstract

While not technically a numbered VCE publication, this is produced by a group of extension specialists in the southeastern region. CALS is a member of the Southeastern Small Fruit Consortium, the producer of this guide Published version

Published
2016

41. The cytochrome P450 lanosterol 14[alpha]-demethylase gene is a demethylation inhibitor fungicide resistance determinant in Monilinia fructicola field isolates from Georgia

Author

Chao-Xi Luo and Schnabel, Guido

Subjects
Fungi -- Genetic aspects, Fungicides -- Research, Gene expression -- Research, Drug resistance in microorganisms -- Research, Biological sciences
Abstract

The role of the 14[alpha]-demethylase gene (MfCYP51) and the ATP-binding cassette transporter gene MFABC1in conferring demethylation inhibitor (DMI) fungicide resistance in field isolates with resistance to propiconazole is examined. The results have shown that overexpression of the MfCYP51 gene is very important in conferring DMI fungicide resistance in Monilinia fructicola field isolates from Georgia and that this overexpression is correlated with Mona located upstream of the MfCYP51 gene.

Published
2008

47. Web application and smartphone-supported disease management in strawberry fields

Author

Schnabel, Guido

Subjects
Hongos fitopatógenos, Disease management, Web application, Smartphone app, Strawberry
Abstract

Botrytis cinerea and Monilinia fructicola, the causal agents of gray mold and brown rot diseases, are one of the most important plant-pathogenic fungi affecting strawberry and peach, respectively. During the last decade, control of both diseases in the southeastern United States has largely been dependent on the use of at-risk fungicides with single-site modes of action. The appearance of gray mold and brown rot, despite applications of fungicides, have been reported by strawberry and peach growers in several states, especially during highly favorable conditions, enhancing concerns about the presence of fungicide-resistant isolates of B. cinerea and M. fructicola in the region. A regional resistance-monitoring program was implemented to help growers determine location-specific resistance profiles. They were originally used to serve South Carolina and Georgia growers, but the service soon became so popular among specialists and growers that, in 2014, growers from 10 states, including Maryland, Pennsylvania, Virginia, West Virginia, North Carolina, South Carolina, Florida, Georgia, Arkansas, and Connecticut used the service. The service provides precise information that has not been available before and enables producers to adjust spray programs before fungicide resistance causes crop loss. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.

Published
2015

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