Effect of Symptom Variants Derived from the NY-MAV Isolate of Barley Yellow Dwarf Virus on the Life Cycle of the English Grain Aphid (Homoptera: Aphididae) and on Yield Components in Wheat and Oats

The NY-MAV isolate of the barley yellow dwarf virus typifies virus isolates transmitted specifically by the English grain aphid, Sitobton avenae (F.). Recently, variants differing in serotypical properties of symptomatology have been isolated by subculture from it. Two symptom types so far differentiated, referred to as ‘notch’ and ‘red’, also cause differential feeding behavior in aphids. This paper describes differential effects of these subcultures of a serologically distinct subculture called NY-MAV-PSl, and of the NY-MAY isolate, on the life cycle of S. avenae feeding on infected oat plants. Aphids developed better on virus-infected than noninfected plants, and plants infected with the ‘notch’ subculture provided the best conditions for overall insect development. Also described are comparisons of the effects of these cultures on yield components in cultivars of spring wheat, Triticum aestivum L. em. Thell., and oat, Avena sativa L. Wheat and oat plants were affected by all the variants, but yield reduction in ‘Butte 86’ wheat plants infected with the ‘red’ and ‘notch’ subcultures mainly resulted from lower production of grains, whereas the production of shriveled grains contributed more significantly to yield reduction in the plants infected with the NY-MAV and MAV-PSI isolates. With ‘Clintland 64’ oat plants, greater reductions in plant size, grain number, and grain weight occurred in plants infected with the ‘red’ and ‘notch’ subcultures than in plants infected with the other isolates.