The Response of Cereals to Increased Dosage with Barley Yellow Dwarf Virus

Abstract

Herta barley [Hordeum distichum], Rodney oats [Avena sativa] and Selkirk wheat [Triticum aestivum] were infested at the 3-leaf stage for 2 days with 1, 20 or 100 individuals of Rhopalosiphum padi or R. maidis carrying, respectively, nonspecific barley yellow dwarf virus (BYDV) isolate 6801 and R. maidis-specific BYDV isolate 7005. Yield reductions were large and significant for the oats infected with either isolate and for the barley infected with isolate 6801, moderate for the barley infected with isolate 7005 and small for the wheat infected with either isolate. With increased numbers of aphids per plant, more plants became infected, the incubation period decreased progressively and symptoms were more severe. Seed yield decreased progressively with increased numbers of aphids where yield reductions were large. Similar dosage-responses occurred in several other yield components such as number of seeds, mean seed weight, number of fertile heads and length of the main culm and its head. For barley infected with isolate 7005 and wheat infected with either virus isolate, trends in seed yield per plant with increasing trends were observed in most of the variables measured on the main culm. The number of fertile heads on wheat increased progressively with larger numbers of aphids. Feeding by 1, 20 or 100 individuals of virus-free R. padi or R. maidis for 2 days caused no yield reductions.