Abstract
Fertilizer did not increase the yield of grain or straw of severely BYDV-infected susceptible oats. A tolerant oat line (Pendek) benefited from fertilizer even when BYDV-inoculated, though with lower efficiency than when it was not inoculated. The harvest index (grain weight/total weight of aerial parts) was changed slightly by fertilizer application, but it was a good indicator of plant tolerance to BYDV regardless of soil fertility.