Introduction
Gibberella ear rot concerns the industry because of DON concentrations. It is well known that DON concentrations are highly dependent on interactions among hybrids, pathogens, and the environment. Starting in 2019, the Ontario Corn Committee (OCC) refined protocols for testing hybrid sensitivity to DON accumulation with confidence based on an assessed risk. This inaugural report provides a risk assessment of hybrids entered in the 2023 trials, along with a multi‐year assessment on the same hybrids if data were available. The current testing method was designed to identify the hybrid‐specific relative resistance of hybrids across multiple environments produced at 2 locations and 3 planting dates at each location per year. The variability inherent in this work was sufficiently constrained to support statistical differences among hybrid entries. It needs to be emphasized that this is a relative risk assessment of hybrids and that additional data sources (e.g., seed company information, field trial results, etc.) should be used for better hybrid decisions based on DON risk. Currently, there are no DON‐resistant hybrids.
Notes on inoculation trials
Briefly, the hybrids were voluntarily submitted by seed companies for testing from 2019 to 2023. Hybrids were tested in misted, inoculated disease nurseries at the Ridgetown Campus from 2019 through 2023, at the Huron Research Station (Exeter) from 2021 to 2023, and at AAFC‐Ottawa in 2019. After 2019, it was determined that the Ottawa location was too far removed from the maturity zone of most hybrids, so trials were conducted at Ridgetown and Exeter in subsequent years. The hybrid entries varied each year depending on seed company decisions and hybrid turnover in the marketplace. Some seed companies chose not to participate in this study, while others entered only a few hybrids. Each hybrid entry was planted on three dates to expose various hybrid maturities to different weather conditions around silking and during grain‐fill: relatively early (early to mid‐ May), mid (late May), and relatively late (early to mid‐June), with three replications per planting date. Thus, each hybrid entry was exposed to six “environments” (two locations × three planting dates) with three replications for a total of 18 DON measurements per hybrid per year in most years. In 2023, the late‐planted block at the Huron Research Station was not inoculated and was subsequently discarded because of late silking.
In all years, corn was planted in 30” rows to achieve a final stand of 34,400 plants per acre (Figure 1). Each hybrid was planted in a single row of approximately 25 plants. Ten plants were inoculated in each row by hand at the optimal time for infection (from full silk to the first sign of silk browning). The trials were mist‐irrigated on timers every day for approximately four weeks after inoculation (Figure 2). At harvest, corn was hand‐harvested, dried, shelled, and analyzed for DON.
Data were analyzed using PROC GLIMMIX with a lognormal distribution. Indices were calculated and compared based on the log means relative to the same (highly DON susceptible) check hybrid. In 2023, hybrids that were statistically different from the check hybrid were identified within each planting date. In the multi‐year combined analysis, data were combined across all environments. Each combination of year, location, and planting date was treated as an “environment” in the analysis as a random effect.
Results
The data were analyzed over multiple years (Table 1) if data were available. The 1‐year column is identical to the last column in Table 2 (i.e., 2023 data). Note that the hybrids were sorted according to the CHU rating. In general, hybrids with multi‐year data ranked similarly across years using only 2 years of data, with only a few exceptions. Of the 45 hybrids entered in 2023, the DON in 16 hybrids was similar to the DON in the susceptible check (note “nd” or “not different” statistically in the last column to the right). Two hybrids were statistically higher than the susceptible check (note “+” in the last column).
A relative risk assessment of hybrid susceptibility to DON is presented as indices by environment in 2023 (see Table 2). The environments are based on location and planting dates. As expected, there was some variability across the five environments; however, there was sufficient consistency or evidence to identify statistical differences in hybrid sensitivity to DON accumulation.
For further information, please contact Dr. Dave Hooker (UG‐Ridgetown) Email: dhooker@uoguelph.ca, or Albert Tenuta (OMAFRA Field Crops Pathologist) Email: albert.tenuta@ontario.ca
Acknowledgements
Ontario Corn Committee, Grain Farmers of Ontario, OMAFRA, OCC DON sub‐committee, seed corn companies (listed below), Agricultural Research Institute of Ontario (ARIO) for research station infrastructure, Canadian Seed Trade Association (CSTA), and in alphabetical order: Dr. Nasim Alijanimamaghani (UG‐Ridgetown), Ahmed Alim (UG‐Ridgetown), Jonathan Brinkman (UG‐Ridgetown), Josh Cowan (GFO), Darrell Galbraith (UG‐Ridgetown), Scott Jay (UG‐Ridgetown‐OMAFRA), Dr. Katiana Eli (UG‐Ridgetown), Michael Heaman (UG‐Ridgetown), David Morris (OCC), Todd Phibbs (UG‐Ridgetown), Ben Rosser (OMAFRA), Dr. Art Schaafsma (UG‐Ridgetown), Carlene Scott (UG‐Ridgetown), Cheryl Van Herk (UG‐Ridgetown/OMAFRA), Ken Van Raay (UG‐Ridgetown), Marty Vermey (GFO), and many summer students.
Sponsors
| Brand or identification, participating seed companies (2019‐2023) | |
| Brevant, Corteva Agriscience | NK Brand, Syngenta Seeds Inc. |
| Country Farm, Country Farm Seeds Ltd. | Pioneer, Pioneer Hi‐Bred Canada |
| CROPLAN, Winfield United | PRIDE Seeds, AgReliant Genetics Inc. |
| DEKALB, Bayer CropScience Inc. | Saatbau, Saatbau Linz |
| Maizex, Maizex Seeds Inc. | |