INTEGRATED STRIPE RUST MANAGEMENT OF BREAD WHEAT

Stripe rust, caused by Puccinia striiformis f. sp. tritici, affects wheat production in Canada. Two effective strategies to control this disease are the deployment of cultivars with stripe rust resistance, and the use of fungicides when susceptible and moderately resistant cultivars are grown under high stripe rust risk conditions.\nThe effect of fungicide application timing on hard red spring wheat cultivars varying in stripe rust resistance was determined at two seeding dates in central Saskatchewan from 2012 to 2016. Under high disease pressure at a mid-May seeding date, a single fungicide application at the mid-flower growth stage of wheat decreased disease severity to 26% compared with the unsprayed control at 87% for the susceptible cultivar ‘AC Barrie’; the magnitude of the response was somewhat less for the moderately resistant cultivar ’CDC Imagine’. There was a significant yield increase of 59% when the fungicide was applied to the susceptible cultivar at mid-flower. Similar effects of fungicide application were observed for protein content, test weight and thousand-kernel weight. Furthermore, at a later seeding date (early June) fungicide application at stem elongation and at mid-flower growth stages of wheat had the same positive effect of reducing stripe rust symptoms from 87% to 51 and 54% and increasing yield by 53 and 46%, respectively for the susceptible cultivar “AC Barrie’. A fungicide application had no effect on the stripe rust resistant cultivar ‘Lillian’ at either seeding date; however, it did reduce leaf-spotting diseases on this cultivar. The study demonstrated that a single fungicide application reduces stripe rust severity, increases yield and improves grain quality in the susceptible and moderately resistant wheat cultivars used in this experiment at the mid-May seeding date. At the early June seeding date, fungicide reduced disease severity of the susceptible and moderately resistant cultivars, but increased yield only for the susceptible cultivar.\nSpelt (Triticum aestivum ssp. spelta), a sub-species of wheat, has been included in varietal development programs because its unique genetic composition makes it easy to cross with bread wheat to introgress desirable traits such as improved grain quality and stripe rust resistance. It has been found that spelt carries race-specific resistance gene Yr5, which confers resistance to all known P. striiformis f. sp. tritici races in North America. The stripe rust resistance of two spelt genotypes, CDC Silex and 10Spelt17, was studied by analyzing populations from crosses with the susceptible bread wheat cultivar ‘Avocet’. Based on growth chamber testing, the adult plant resistance of these spelt genotypes was shown to be conferred by at least two genes.

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