SUSCEPTIBILITY TO THE YELLOW DWARF VIRUS OF BARLEY VARIETIES GROWN IN MANITOBA, AND ASSESSMENT OF AFRICAN VARIETIES FOR TOLERANCE

Four six-rowed varieties of barley (Hordeum vulgare L.), Husky, Jubilee, Keystone and Montcalm, and one two-rowed variety (H. distichum L.), Herta, grown commercially in Canada, were moderately to highly susceptible to barley yellow dwarf virus (BYDV) when tested in the greenhouse. Controlled inoculation with BYDV in the field resulted in seed weight losses of 79 and 67%, respectively, on two other six-rowed varieties, Parkland and Conquest. Three of 14 African barley varieties that previously had been found resistant to net blotch caused by Pyrenophora teres Drechs. were highly tolerant to BYDV when tested in a growth cabinet. When the most tolerant (C.I. 5791), the most susceptible (C.I. 9584), and one of intermediate susceptibility (C.I. 5810) of these African varieties were subsequently tested to the same virus isolate in the field, they rated in the same order of susceptibility as in the growth cabinet. Symptom ratings were not indicative of the effect of the virus on seed yield; hence, the varietal reactions were based on yield reduction.