Corn hybrid DON evaluation

Objectives:

• To address key research and knowledge gaps regarding corn hybrid susceptibility to deoxynivalenol (DON) and develop effective screening protocols to reliably determine the susceptibility of hybrids.

Impacts:

• More reliable evaluations of corn hybrids to DON mycotoxin accumulation will improve farmer and industry capacity to manage Gibberella ear rot (GER) and DON levels.

Scientific Summary:

Hybrid differences in deoxynivalenol (DON) accumulation have been observed as an opportunity to manage DON in corn production, but growers have no reliable resource for selecting hybrids that may be less susceptible to accumulate DON. In 2018, an epidemic of Gibberella ear rot (GER) caused tremendous losses to the industry due to high DON concentrations and the corn industry stakeholders developed a prioritized list of needs for managing future outbreaks. The Ontario Corn Committee (OCC) moved to analyze 1,225 grain samples for DON across 136 hybrids in 2018. The analysis supported previous research with highly statistically significant hybrid effects on DON. In general, it was a favourable find that hybrids with the highest concentration of DON tended to be consistent across all locations, but there were exceptions. The OCC, therefore, moved to test and refine protocols for future testing of hybrid sensitivity to DON accumulation in favourable environments in inoculated-misted trials.

In 2021 and 2022, corn hybrids were tested at Ridgetown Campus (Ridgetown) and at a new misted nursery site at the Huron Research Station (Exeter).

Results:

• In 2022, for the first time since starting this work, the team achieved a good separation and grouping of hybrids that were consistently as susceptible or more susceptible to the check and also a clear group of those that are less susceptible. This work was laborious, requiring careful attention to detail and timelines.
• 2022 had the most consistent infection in the field to date, even though the levels of infection varied across planting dates and locations. There were no significant differences in DON accumulation in the inoculated susceptible check across locations and environments, showing that inoculating all the plots at the optimum time of silk browning appropriately challenged each hybrid.
• In 2022, more consistent concentrations of DON accumulation were observed relative to the susceptible check across environments than any other time the tests have been run. 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.
• Regarding environment, a very narrow window with a fairly precise set of moisture and temperature conditions is needed to get an individual ear 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.
• Planting on 3 dates, approximately 2 weeks apart, was determined to be effective at spreading out the silking dates, which essentially tested each hybrid across 3 “environments” at each location. The trial needs to continue to plant 3 dates across two locations (Ridgetown and Huron research stations) to ensure conducive environments are captured.
  • However, it needs to be understood that differences by planting date do not imply DON is less or more if corn is planted early or late; all planting dates represent different environments when weather may be more or less favorable for GER and DON accumulation across hybrids of varying maturities. Planting dates will be addressed as environments moving forward (e.g., not as a comparison of planting dates).
• The crop heat unit (CHU) rating of a hybrid impacts how much DON accumulates, with the earliest maturing hybrids tending to accumulate the least and later maturing hybrids the most DON. This is likely due to the length of time that the ear is susceptible to infection and colonization. Quicker maturing hybrids (early drydown) would have a shorter period of exposure while slower maturing hybrids (longer drydown) would have a longer period of exposure. The phenomenon’s intensity varied with environment (planting date) and location but consistently showed greater DON accumulation in later maturing hybrids.
• The amount of work to carry out the trial each year was achievable but the bottleneck in getting data out on time in the Fall was the time it took to process the samples and do the analyses. It took about 3.5 weeks from the start of harvest to having the data available, with 6-7 people helping during the first two weeks, dwindling down to 2 or 3 toward the end. It then took about 2-3 days to sort out, analyze and tabulate the data.
• Whole plots of ten ears were harvested but it was 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, there were more “hits and misses” from each plot. In 2022, the number of hits was more consistent so the research team 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:

This project was funded in part by the Canadian Agricultural Partnership, a five-year investment by Canada’s federal, provincial and territorial governments.

Various seeds companies.  

Various end users.

Project Related Publications:

Project results established the protocol for the 2023-onward corn hybrid rankings of susceptibility to DON that are released on https://corn.gocrops.ca at the end of each year.