Phenotypic and genotypic characterization of a hyper-localized population of Macrophomina phaseolina

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2023-12
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Allgaier, Katie Diann
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Harris, Steven
Halverson, Larry
Leandro, Leonor
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Plant Pathology
Abstract
Macrophomina phaseolina is a fungal plant pathogen that is the causative agent of the charcoal rot in soybeans. In this study, isolates of M. phaseolina all obtained from the same farm were tested for growth at 26°C, 30°C, 34°C, 38°C, and 42°C. Additionally, all isolates were tested for carbon utilization against 32 carbon sources. Results showed that temperature increases did not decrease M. phaseolina growth until reaching 42°C. Some isolates were still able to grow at 42°C on yeast dextrose peptone (YPD) agar, demonstrating an increased heat tolerance compared to other isolates tested. Carbon utilization testing demonstrated that the carbon sources commonly found in plant material caused the greatest hyphal growth, such as D-xylose, L-rhamnose and D-cellobiose. Three representative isolates were then chosen for assessing fungicide sensitivity using the Pandemic Response Box, and six compounds – AN 2718, butenafine, carbendazim, everolimus, 5-fluorocytosin, and fenbendazole – were chosen for further testing based on efficacy and mode of action. Initial fungicide screening revealed eleven fungicidal compounds that were effective against M. phaseolina growth. Of the six compounds that were further tested, carbendazim was found to be the most effective. AN2718 and 5-fluorocytosin had very similar effectiveness as carbendazim at higher concentrations but were not as effective at lower concentrations (<10µM). Genomic DNA from the three representative isolates was then sequenced using Illumina MiSeq, and variant calling was performed. Variant calling indicated over 1.1 million single nucleotide polymorphisms, of which 36.72% were shared among all three isolates. Together, these results help demonstrate the phenotypic and genetic variability that can exist within hyper-localized populations of M. phaseolina and reveal potential avenues for controlling M. phaseolina growth.
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