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Root Disease Profiling Service – In response to Dr. Mitkowski

Dear Friends of Turfgrass Industry,

Thanks for visiting my site.

If you are looking for root disease profiling services, please visit this page.

If you are directed through the link sent by Dr. Nathaniel Mitkowski and are interested to learn more about this concern on S. cylindrosporus being an emerging turfgrass pathogen, then please continue reading.

As a scientist who is eager to learn and provide research-driven and practical information for the turfgrass community, I welcome all discussions on the science. I also embrace challenges and disagreements when there is up-to-date data to support them. However, I do not accept criticism without the intention to engage in scientific discussion and laying out the scientific facts.

First, I would like to share the Koch’s postulate image here. These photos of inoculated pots were taken 10 weeks post-inoculation of S. cylindrosporus under moderate drought and heat stress. Codes in between pots indicate different isolates obtained from ERI-fungi infected turfgrass sampled sent through RUPDL where S. cylindrosporus being the sole plausible causal agent examined using culture-dependent and -independent methods. The bottom labels indicate the turfgrass species. Of course this is only visual presentation here but I am happy to share quantitative results with anyone who’s interested. I can also share the isolates and protocol used in this study for those who’d like to replicate this work.

 

Here are the potential reasons why I think Dr. Mitkowski perceived S. cylindrosporus as a non-pathogen.

  1. The isolates Dr. Mitkowski worked on may not have been true S. cylindrosporus. Our understanding of fungal phylogeny has evolved quickly over the past 20 years. A classic example is dollar spot causal agent whose phylogeny has drastically changed since the past decade, with new information emerging almost every year that reshape our understanding of this important disease. For ERI fungi, classification of genera and species within the Magnaporthaceae family shifted drastically with many turf pathogenic genera re-classified multiple times. While microscopic examination of the disease signs remained critical for proper diagnosis, distinguishing closely related or even previously unknown fungal species can be extremely difficult, and sometimes impossible, without proper molecular identification. Many of the molecular tools available today either didn’t exist or weren’t accessible to plant pathologists 37 years ago, which is when the research Dr. Mitkowski referenced was conducted.
  2. Our Koch’s postulate conditions may be very different from what was done 20 or 37 years ago, as the understanding of patch diseases has progressed so much over time. We now know that soil physicochemical and biological conditions play critical roles in ERI-fungal diseases. We carefully controlled factors such as soil pH, plant available moisture, disease-promoting fungicides, and ambient temperature to mimic stressful field conditions and encourage disease development in our Koch’s postulate. In addition, we conducted prolonged incubation for up to 16 weeks, knowing S. cylindrosporus generally doesn’t grow as fast as conventional summer patch causal agent M. poae.
  3. Contemporary turfgrass management practices may have selected pathogenic S. cylindrosporus that have become more virulent over the years. Evolution of fungal pathogen virulence and pathogenicity, and shifts in pathogen populations are well documented in many plant pathogens. I do not have any evidence to support virulence evolution or population shifts of S. cylindrosporus, nor do I have evidence to reject this possibility.

Since joining the turfgrass industry and the field of turfgrass pathology in 2019, I have experienced nothing but support and kindness from this great community. I am extremely grateful every single day for the opportunity to work with turfgrass stakeholders and scientists. Criticism only reminds me to be open-minded and kind, and it motivates me to become a better scientist and person. My collaborators, graduate students, and I will continue to work on this project with the goal to make the latest technology available to the industry and generate research-driven and practical information to advance the turfgrass industry.

 

Sincerely,

Ming-Yi Chou