The system used to rate a wheat variety’s tolerance to fusarium head blight (FHB) is science based, but it doesn’t mean ratings don’t sometimes change, Pam de Rocquigny told farmers here Jan. 21 at Ag Days.
“They change for two reasons – there is further testing in the co-op trials… and because of performance in commercial fields,” Manitoba Agriculture, Food and Rural Initiatives’ (MAFRI) business development manager for feed grains said.
Pathologists with Agriculture and Agri-Food Canada assess and rate wheats for fusarium tolerance during the three years they’re in co-operative trials. Those trials are required before a new variety can be recommended for registration – a prerequisite to commercial production.
New wheats are grown in replicated, irrigated plots where fusarium inoculum is sprayed twice on the wheat heads. The first spray occurs when the majority of plants are at 50 to 75 per cent anthesis, followed by a spray two days later. The plants, which are in single rows, are sprayed each time on one side and then the other to be sure they are well covered, de Rocquigny said.
The plants are assessed in 18 to 21 days. First, researchers measure how many heads are infected (disease incidence), then each head is inspected to the extent of the infection (disease severity).
From those two numbers a visual rating index is created so the disease tolerance of new varieties can be compared against check varieties and is given a rating such as “poor,” “fair” or “good.”
Tested varieties are hand-harvested to avoid contamination and assessed for the percentage of damaged kernels due to fusarium as well as the level of DON.
“All this information is looked at by the disease evaluation team meeting at the February meeting of the Prairie Grain Development Committee,” de Rocquigny said.
This fusarium rating for CDC Go, a Canada Western Red Spring wheat registered in 2004 and released to seed growers to multiply in 2006, dropped to “poor” this year from “fair” after plant pathologists saw how it was decimated by FHB last year.
“Based on our disease checks, (CDC Go) looked like it was fair to moderately resistant,” said Jeannie Gilbert, a plant pathologist with Agriculture and Agri-Food Canada’s Cereal Research Centre in Winnipeg, in an interview last fall. “It was there for three years (of testing) and each year it was fairly consistent in terms of being the best of that bunch.
“None of the tests prior to this year indicated that it was going to be so susceptible.”