An assay to reliably achieve Tar Spot symptoms on corn in a controlled environment

Breuing, Mikaela; Bittner, Richard; Dolezal, Andrea L.; Ramcharan, Amanda; Bunkers, Greg J

doi:10.1101/2023.01.12.523803

Cited by 3 publications

(7 citation statements)

References 5 publications

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“…Our data are like those of Hock et al 11 , in that RH was very important in predicting P. maydis development, however, the work presented here suggests that extended periods of high RH are antagonistic to the development of tar spot. These findings seem consistent with Breunig et al 12 that only intermittent periods or wetness are neded to support the development of tar spot. Thus, the results presented here refine our understanding of the role RH plays in the epidemiology of tar spot in the U.S.…”

Section: Discussionsupporting

confidence: 92%

“…Interestingly these moisture variables are negatively correlated with increasing TS severity. Breunig et al 12 point out that in controlled-environment inoculations frequent misting was only required in the first 5 days after inoculation. After 5 days, misting had to be withheld to produce stroma in these controlled environments.…”

Section: Discussionmentioning

confidence: 99%

“…Monthly temperatures of 17–22 °C, relative humidity greater than 75%, leaf wetness of 7 h per night and 10–20 foggy days per month were reported as the optimal conditions for tar spot development 11 . Under controlled environments and optimal conditions, inoculation assays demonstrated a latent period of only 15 days, and sporulation occurring approximately 20 days post-inoculation 12 .…”

Section: Introductionmentioning

confidence: 99%

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Uncovering the environmental conditions required for Phyllachora maydis infection and tar spot development on corn in the United States for use as predictive models for future epidemics

Webster,

Nicolli,

Allen

et al. 2023

Sci Rep

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Phyllachora maydis is a fungal pathogen causing tar spot of corn (Zea mays L.), a new and emerging, yield-limiting disease in the United States. Since being first reported in Illinois and Indiana in 2015, P. maydis can now be found across much of the corn growing regions of the United States. Knowledge of the epidemiology of P. maydis is limited but could be useful in developing tar spot prediction tools. The research presented here aims to elucidate the environmental conditions necessary for the development of tar spot in the field and the creation of predictive models to anticipate future tar spot epidemics. Extended periods (30-day windowpanes) of moderate mean ambient temperature (18–23 °C) were most significant for explaining the development of tar spot. Shorter periods (14- to 21-day windowpanes) of moisture (relative humidity, dew point, number of hours with predicted leaf wetness) were negatively correlated with tar spot development. These weather variables were used to develop multiple logistic regression models, an ensembled model, and two machine learning models for the prediction of tar spot development. This work has improved the understanding of P. maydis epidemiology and provided the foundation for the development of a predictive tool for anticipating future tar spot epidemics.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Uncovering the environmental conditions required for Phyllachora maydis infection and tar spot development on corn in the United States for use as predictive models for future epidemics

Webster,

Nicolli,

Allen

et al. 2023

Sci Rep

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show abstract

“…Interestingly these moisture variables are negatively correlated in our work. Breunig et al 12 point out that in controlled-environment inoculations frequent misting was only required in the first five days after inoculation. After five days, misting had to be withheld to produce stroma in these controlled environments.…”

Section: Discussionmentioning

confidence: 99%

“…Monthly temperatures of 17°C – 22°C, relative humidity greater than 75%, leaf wetness of seven hours per night and 10-20 foggy days per month were reported as the optimal conditions for tar spot development 11 . Under controlled environments and optimal conditions, inoculation assays demonstrated a latent period of only fifteen days, and sporulation occurring approximately twenty days post-inoculation 12 .…”

Section: Introductionmentioning

confidence: 99%

Uncovering the Environmental Conditions Required forPhyllachora maydisInfection and Tar Spot Development on Corn in the United States for Use as Predictive Models for Future Epidemics

Webster

Nicolli

Allen

et al. 2023

Preprint

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Phyllachora maydis is a fungal pathogen causing tar spot of corn (Zea mays L.), a new and emerging, yield-limiting disease in the United States. Since being first reported in Illinois and Indiana in 2015, P. maydis can now be found across much of the corn growing of the United States. Knowledge of the epidemiology of P. maydis is limited but could be useful in developing tar spot prediction tools. The research presented here aims to elucidate the environmental conditions necessary for the development of tar spot in the field and the creation of predictive models to anticipate future tar spot epidemics. Extended periods (30-day windowpanes) of moderate ambient temperature were most significant for explaining the development of tar spot. Shorter periods (14- to 21-day windowpanes) of moisture (relative humidity, dew point, number of hours with predicted leaf wetness) were negatively correlated with tar spot development. These weather variables were used to develop multiple logistic regression models, an ensembled model, and two machine learning models for the prediction of tar spot development. This work has improved the understanding of P. maydis epidemiology and provided the foundation for the development of a predictive tool for anticipating future tar spot epidemics.

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A new and effective method to induce infection of Phyllachora maydis into corn for tar spot studies in controlled environments

Solórzano,

Issendorf,

Drott

et al. 2023

Plant Methods

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Background Tar spot of corn is a significant and spreading disease in the continental U.S. and Canada caused by the obligate biotrophic fungus Phyllachora maydis. As of 2023, tar spot had been reported in 18 U.S. states and one Canadian Province. The symptoms of tar spot include chlorotic flecking followed by the formation of black stromata where conidia and ascospores are produced. Advancements in research and management for tar spot have been limited by a need for a reliable method to inoculate plants to enable the study of the disease. The goal of this study was to develop a reliable method to induce tar spot in controlled conditions. Results We induced infection of corn by P. maydis in 100% of inoculated plants with a new inoculation method. This method includes the use of vacuum-collection tools to extract ascospores from field-infected corn leaves, application of spores to leaves, and induction of the disease in the dark at high humidity and moderate temperatures. Infection and disease development were consistently achieved in four independent experiments on different corn hybrids and under different environmental conditions in a greenhouse and growth chamber. Disease induction was impacted by the source and storage conditions of spores, as tar spot was not induced with ascospores from leaves stored dry at 25 ºC for 5 months but was induced using ascospores from infected leaves stored at -20 ºC for 5 months. The time from inoculation to stromata formation was 10 to 12 days and ascospores were present 19 days after inoculation throughout our experiments. In addition to providing techniques that enable in-vitro experimentation, our research also provides fundamental insights into the conditions that favor tar spot epidemics. Conclusions We developed a method to reliably inoculate corn with P. maydis. The method was validated by multiple independent experiments in which infection was induced in 100% of the plants, demonstrating its consistency in controlled conditions. This new method facilitates research on tar spot and provides opportunities to study the biology of P. maydis, the epidemiology of tar spot, and for identifying host resistance.

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An assay to reliably achieve Tar Spot symptoms on corn in a controlled environment

Cited by 3 publications

References 5 publications

Uncovering the environmental conditions required for Phyllachora maydis infection and tar spot development on corn in the United States for use as predictive models for future epidemics

Uncovering the environmental conditions required for Phyllachora maydis infection and tar spot development on corn in the United States for use as predictive models for future epidemics

Uncovering the Environmental Conditions Required forPhyllachora maydisInfection and Tar Spot Development on Corn in the United States for Use as Predictive Models for Future Epidemics

A new and effective method to induce infection of Phyllachora maydis into corn for tar spot studies in controlled environments

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