Interaction between barley yellow dwarf virus and powdery mildew in four barley genotypes

Abstract

SUMMARYThe effect of infection by barley yellow dwarf virus (BYDV) on host reaction to powdery mildew (Erysiphe graminis DC. f. sp. hordei Marchal) in four barley genotypes with different types of resistance to barley mildew isolate AB3, was studied in pot‐grown plants at 7,12 and 26 days after mildew inoculation. Cv. Engledow India (hypersensitive resistance) showed necrotic spotting only at the third scoring date, but the area showing symptoms was significantly less in BYDV‐infected than in control plants. On Vada (intermediately resistant), the reaction type value (a measure of host/pathogen compatibility), the percentage leaf area covered with mildew and the coefficient of infection (C.I., a mathematical combination of the other two characters mentioned) were initially less and subsequently greater on BYDV‐infected than on virus‐free plants. However, the initial trend was significant only for reaction type and C. I., and the subsequent trend only for percentage mildew cover and C.I. Reaction type values, percentage mildew cover and C.l. on cv. Emir (susceptible with some degree of adult plant resistance) and cv. Golden Promise (very susceptible) were also initially significantly less on BYDV‐infected plants, but subsequently all three characters increased to amounts not significantly different from those on virus‐free plants.