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Differential Effects of Barley Yellow Dwarf Virus on the Physiology of Tissues of Hard Red Spring Wheat. Stanley G. Jensen, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Department of Botany and Biology, South Dakota State University, Brookings 57006; Jerome W. Van Sambeek, Research Assistant, Department of Botany and Biology, South Dakota State University, Brookings 57006. Phytopathology 62:290-293. Accepted for publication 30 September 1971. DOI: 10.1094/Phyto-62-290.

Three cultivars of hard red spring wheat which varied in their response to barley yellow dwarf virus infection were grown in the field in the summer of 1969. Plants were infested with viruliferous aphids in the seedling stage. When the plants reached the late milk or early soft-dough stage of maturity, photosynthetic rates, respiratory rates, and the accumulation of dry matter were measured in tissues above the top vegetative node. The most susceptible cultivar contained 42% excess dry weight in the flag leaf blade where there was a 72% reduction in photosynthetic capacity and a 36% stimulation of respiration. Similar tissues of a resistant cultivar showed only 20% excess accumulation of dry weight, 60% reduction in photosynthesis, and a 20% reduction in respiration. Among the tissue classes, the flag leaf blades were severely affected and the leaf sheaths moderately affected, while no significant effect was measured on the culm and spike. We suggest that most of the yield in infected susceptible plants is derived from photosynthesis of the spike.