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OCC corn hybrid DON/GER evaluations

Principal Investigator: Ontario Corn Committee (OCC)

Research Institution: Ontario Corn Committee (OCC)

Timeline: January 2022 – December 2022   

Objectives:

  • Identify appropriate reliable field screening methods for determining hybrid susceptibility to Gibberella ear rot (GER) and deoxynivalenol (DON) and assess DON susceptibility of commercially relevant corn hybrids.

Impacts:

  • Will enable reliable field screening of corn lines for resistance to GER and DON accumulation so that hybrid resistance can be improved and will eventually enable growers to obtain reliable GER/DON resistance ratings for commercial corn hybrids.

Scientific Summary:

Since 2019, corn seed companies submitted commercially relevant corn hybrids to the OCC to be evaluated by expert researcher teams for susceptibility to DON accumulation. The research was performed in two misted, inoculated nursery field sites at Ridgetown and Huron research stations. The primary goal since 2019 was to develop protocols for an accurate and reliable assessment hybrids for GER/DON risk levels.  Protocols were refined each year from a highly collaborative effort among OCC members that included grower organizations, academia, extension, seed companies and end users. The accuracy of the results was compared to hybrid-specific trends observed among seed companies and other industry representatives on farm and research fields.  After four years of experimentation (2019-2022), members of the OCC were generally pleased with trends of better accuracy and lower variability in hybrid DON assessments, but the committee wishes another year of results (2023) to confirm before the hybrid assessments are made public. The OCC anticipates that ratings of commercial corn hybrids to DON accumulation will be released in early 2024 if 2023 proves successful.  This information would be extremely valuable to assist growers in making hybrid-selection decisions to manage DON risk.

2022 Results

  1. The 2022 OCC Hybrid Performance for DON study yielded significant findings regarding natural infection patterns and DON accumulation across different planting sites and dates. Natural infection occurred at most sites and planting dates. The field site nursery at Huron Research Station exhibited significantly less DON accumulation compared to Ridgetown likely due to being planted after soybean, which resulted in reduced natural inoculum. In contrast, the Ridgetown location showed significantly higher DON accumulation, attributed to following heavily infected continuous corn.
  2. Significant differences in DON accumulation were observed among planting dates at Ridgetown; this highlights the crucial role of environmental factors around silking. Planting dates were introduced in 2020 to generate datasets with more robust environmental conditions around silking for each hybrid. Similar to previous years, the inoculated susceptible check showed consistent high DON accumulation among locations and planting dates, indicating that inoculation at the optimum time of silk browning effectively challenged each hybrid.
  3. The study revealed that the CHU rating of hybrids influenced DON accumulation, with earlier maturing hybrids tending to accumulate less DON and later maturing hybrids showing higher accumulation. This trend varied in intensity with planting date and location but remained consistent. We hypothesize that this has to do with the length of time that the ear is susceptible to infection and colonization. Quicker maturing hybrids would have a shorter period of exposure while slower maturing hybrids would have a longer period of exposure. The phenomenon’s intensity varied with planting date and location but consistently showed greater DON accumulation in later maturing hybrids.
  4. The 2022 study achieved improved consistency in infection and DON accumulation, with clear separation and grouping of hybrids based on susceptibility relative to the check, and only four hybrids showing major inconsistencies in reaction across environments.  The inconsistencies caused some concern among OCC members.  The trend with CHU may not be a flaw in the protocol but may be related to the susceptibility of the hybrids volunteered by seed companies. 
  5. There were no significant differences in DON accumulation in the inoculated susceptible checks across locations and plant dates, showing that inoculating all the plots at the optimum time of silk browning appropriately challenged each hybrid.
  6. What we know is that temperature needs to be optimized to get good infection.  This was determined by analyzing silk timing across the six environments per year (2 locations x 3 planting dates). Silk inoculations were consistent depending on the timing of inoculation relative to optimum temperature.
  7. In the field we observed the most consistent infection to date, even though the levels of infection varied across planting dates and locations. We also observed more consistent concentrations of DON accumulation relative to the susceptible check across planting dates and locations than any other time we have run these tests. There were only four hybrids that had major flips in reaction. Two of these were both on the susceptible side of the table. And only two of the less susceptible group (significantly different from check) had more (~1.5x) DON in only one of the unique environments compared to the susceptible check in that environment.
  8. For the first-time since we have been doing this work, we achieved a good separation and grouping of hybrids that are definitely and consistently as or more susceptible than the check and also a clear group of those that are less susceptible.
  9. This work is laborious, requiring careful attention to detail and timelines. Much of it is tedious but requires skill and care. We believe we hit upon the right combination this year and going forward if we can duplicate the effort, we should be able to repeat the outcome.

Going Forward

We know that planting on three dates, approximately two weeks apart, was effective at spreading out the silking dates, which essentially tested each hybrid across three unique environments at each location.

  1. We were able to provide results by early December.
  2. We need to spread the risk by continuing to plant on three dates across two locations, with at least 3 replicates of each hybrid within each planting date.
  3. This amount of work is achievable but the bottleneck in getting data out on time. It takes a lot of time to process the samples and to do the analyses during the busy fall season. It took about 3.5 weeks from the start of harvest to the data being available. We had 6-7 people helping during the first two weeks, dwindling down to 2 or 3 towards the end. It takes about 2-3 days to sort out, analyze and tabulate the data.
  4. A second location at the Huron Research Station (HRS) was installed in 2021, thanks to funding from the Agricultural Research Institute of Ontario (ARIO) for infrastructure (misting lines, pumps, timers, water tanks and plumbing). Two locations planted at three planting dates resulted in six unique “environments” for hybrid testing. Similar protocols were used at both Ridgetown and Huron research station locations in 2022.
  5. A very narrow window with a fairly precise set of moisture and temperature conditions is needed to get individual ears infected with Gibberella. Multiple timings of inoculations are needed to capture these conditions. Moisture can be controlled by misting, but the optimum temperature can only be captured by having ears silk at multiple times with inoculations timed to this silking in the hopes that the optimum temperature for infection may be captured.
  6. We have been harvesting whole plots of ten ears but have observed that not all ears in one plot get infected even though all ears are inoculated. It is a function of hits and misses. In 2021, we had more “hits and misses” from each plot. In 2022, the number of hits was more consistent so we decided against the need to combine incidence and severity ratings of ears that can be multiplied by the DON concentration to give a DON index rating.

External Funding Partners:

  • Ontario Ministry of Agriculture, Food and Agribusiness
  • Various corn seed companies through entry fees
  • Various corn end users

Project Related Publications

  • None as of 2022