Plant Fusarium Wilt Resistant Canola

REGINA - Feb 7/05 - SNS -- Canola growers should be choosing varieties which are resistant to Fusarium wilt, asserts Saskatchewan Agriculture's Integrated Cropping Management Specialist Dale Risula.

"Some producers have experienced some major losses during the last couple of years -- as much as 100% in some cases," says Risula. "The disease was first noticed in northern regions of the Peace River area in Alberta in 1999. Since then, Fusarium wilt has been found sporadically in the canola production regions of Saskatchewan and Manitoba as well."

Fusarium wilt infects plants through the roots and plugs their vascular system, limiting the flow of water and nutrients up the stem and leading to stem discoloration. If severely infected, plant death will occur. Often, the symptoms are observed on only one side of the plant, or only affect a few branches.

"One of the challenges," explains Risula, "is that the symptoms are similar to those of drought stress, which makes it difficult to identify. Plants may be stunted, discolored and exhibit poor seed set. Fusarium wilt causes a discoloration of the stem. It is often seen as purple, grey or brown streaks starting from the foot region and moving up the plant."

One of the ways to determine if it is Fusarium wilt is to scrape or cut away the epidermis to look for dark streaks in the vascular tissue running up and down the stem. Often, the infected plants will die prematurely and yield can be greatly reduced.

Fusarium wilt can be differentiated from other canola diseases because roots of affected plants will remain intact, unlike in a case of root rot. There will be no cankers on the stem base or lodging as with blackleg, nor bleaching and shredding of the stems, as with sclerotinia rot.

"The only way to control Fusarium wilt infestations at this point is through disease resistance," says Risula. "There are no registered fungicides to deal with the problem. Fortunately, variety selection -- combined with an appropriate crop rotation program -- is extremely effective. The beauty of it is that selection is that effective."

There is differentiation between varieties of Argentine canola (Brassica napus), which means that breeders will continue to screen this susceptibility out of future varieties.

Canola growers are advised again to check if the variety they choose is resistant to Fusarium wilt before seeding.