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Vector Relations

The Response of Cereals to Increased Dosage with Barley Yellow Dwarf Virus. P. A. Burnett, Former Graduate Student, Department of Entomology, University of Manitoba and Agriculture Canada Research Station, 25 Dafoe Rd., Winnipeg, Manitoba. Senior authorís present address: Crop Research Division, DSIR, Private Bag, Christchurch, New Zealand; C. C. Gill, Research Scientist, Department of Entomology, University of Manitoba, and Agriculture Canada Research Station, 25 Dafoe Rd., Winnipeg, Manitoba. Phytopathology 66:646-651. Accepted for publication 24 October 1975. DOI: 10.1094/Phyto-66-646.

Herta barley, Rodney oats, and Selkirk wheat, were infested at the three-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 of its head. For barley infected with isolate 7005, and wheat infected with either virus isolate, trends in seed yield per plant with increased numbers of aphids were either small or absent, although for the wheat decreasing 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.

Additional keywords: Hordeum distichum L., Avena sativa L., Triticum aestivum L.