The effect of aphid numbers and stage of plant growth in determining tolerance to barley yellow dwarf virus in cereals

Abstract

Abstract Trials in Canada and New Zealand have confirmed that the severity of barley yellow dwarf virus (BYDV) may be varied by inoculation at different stages of growth and by using different numbers of infective aphids. In barley, oats, and wheat, BYDV inoculation with higher aphid numbers was necessary at later growth stages to obtain a similar degree of severity as achieved by low aphid numbers at an early stage of growth. Some cereal varieties are more resistant to BYDV infection at early stages of growth than at later stages, others are more resistant to later inoculation, while the most resistant varieties (from Ethiopia) are resistant at all stages of growth. Inoculation with low aphid numbers at early stages of growth and separately with high aphid numbers at later stages would be necessary to breed cereals with high resistance to BYDV for New Zealand conditions.