Screening for Alternaria brassicicola resistance in the Brassicaceae: Bio-assay optimization and confocal microscopy insights into the infection process
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Abstract
Heavy losses incited yearly by Alternaria brassicicola on the vegetable Brassicaceae – have prompted our search for sources of genetic resistance against the pathogen and the resultant disease, dark leaf spot. We optimized several parameters to test the performance of the plants under controlled conditions to this disease, including leaf age and position, inoculum concentration, and incubation temperature. Using these optimized conditions, we screened a collection of 38 Brassicaceae cultigens with two methods (detached leaf and seedlings). Our results show, that either method can be used for the A. brassicicola resistance breeding, while the plant’s genotype was crucial in determining its response to the pathogen. The laboartory bio-assays for A. brassicicola resistance were run under more stringent conditions than the field tests, and resulted in identification of two interspecific hybrids that might be used in breeding programs. Confocal microscopy analyses of the leaf samples provided data into the pathogen mode of infection: Direct epidermal infection or stomatal attack were related to plants’ resistance against A. brassicicola among the cultigens tested. Further, the actin network of the host cells reorganized around the papillas deposited under the pathogen’s appressorium.
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2016. Screening for Alternaria brassicicola resistance in the Brassicaceae: Bio-assay optimization and confocal microscopy insights into the infection process. PeerJ PrePrints 4:e1360v2 https://doi.org/10.7287/peerj.preprints.1360v2Author comment
This is a preprint submission to PeerJ Preprints.
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Supplemental Information
Supplementary Fig.1: Aggressiveness of A. brassicicola isolate collection, expressed as lesion size [mm2]
Bio-assays were performed on the detached leaves of A. brassicicola-susceptible ‘Kamienna Głowa’ cabbage, evaluated at 7 dpi (see Materials and methods section for details). Raw data for lesion sizes generated by each isolate tested are presented as series of stacked beeswarms, juxtaposed with respective boxplots (median is marked in black; box represent the interquartile range; whiskers extend to cover the rest of the data in each group; outliers are represented as empty white circles). Isolates colored red were combined for inoculum mixture, used in all subsequent experimentation.
Additional Information
Competing Interests
The authors declare that they have no competing interests.
Author Contributions
Marzena Nowakowska conceived and designed the experiments, performed the experiments, analyzed the data, wrote the paper, reviewed drafts of the paper.
Małgorzata Wrzesińska conceived and designed the experiments, performed the experiments, analyzed the data, wrote the paper, reviewed drafts of the paper.
Piotr Kamiński conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Marcin Nowicki conceived and designed the experiments, performed the experiments, analyzed the data, contributed reagents/materials/analysis tools, wrote the paper, prepared figures and/or tables, reviewed drafts of the paper.
Małgorzata Lichocka analyzed the data, contributed reagents/materials/analysis tools, prepared figures and/or tables, reviewed drafts of the paper.
Michał Tartanus contributed reagents/materials/analysis tools, prepared figures and/or tables, reviewed drafts of the paper.
Elżbieta U Kozik analyzed the data, wrote the paper, reviewed drafts of the paper.
Data Deposition
The following information was supplied regarding data availability:
Raw data is included in this submission.
Funding
This work was performed in the frame of Multi-annual Programme "Development of sustainable methods of horticultural production to ensure high biological and nutritional quality of horticultural products and to preserve the biodiversity of the environment and to protect its resources" (2008-2014), and in the frame of multiannual programme "Actions to improve the competitiveness and innovation in the horticultural sector with regard to quality and food safety and environmental protection" (2015-2020), both financed by Polish Ministry of Agriculture and Rural Development. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
