Tests for leaf rust resistance conditioned by Lr16 were done at the seedling stage as previously described [25 (link)]. Seeds were planted in clumps of approximately 10 seeds evenly spaced in fibre flats (25 × 15 cm). Approximately 14 d after seeding, the seedlings at the two leaf stage were inoculated with urediniospores of P. triticina isolate 12–3 MBDS (nomenclature as previously described [26 (link)]) mixed with a light mineral oil (Bayol, Esso Canada, Toronto, ON) sprayed onto the leaves using a compressed air sprayer. This P. triticina isolate is fully avirulent on Lr16 carriers. The plants were allowed to dry, to evaporate the mineral oil, for at least 1 h then moved to a 100% humidity cabinet for approximately 17 h of incubation. The plants were then moved to a greenhouse at 20 ± 4 °C with supplemental lighting. After approximately 14 d, plants were rated for symptoms using a ‘0’ to ‘4’ infection scale where ‘0’ (no symptoms), ‘;’ (hypersensitive flecks), ‘1’ (small uredinia with necrosis), and ‘2’ (small to medium-sized uredinia with chlorosis) were considered resistant responses and ‘3’ (medium-sized uredinia without necrosis or chlorosis) and ‘4’ (large-sized uredinia without necrosis or chlorosis) were considered susceptible responses [26 (link)].
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