SUSCEPTIBILITY OF COMMON AND DURUM SPRING WHEATS TO BARLEY YELLOW DWARF VIRUS

Nine varieties of common wheat (Triticum aestivum L.) and four varieties of durum wheat (T. durum Desf.) were inoculated with three isolates of barley yellow dwarf virus (BYDV) in the greenhouse. All varieties proved susceptible to BYDV, and yields were severely reduced. Yellow discoloration and chlorosis of leaves was slight in most varieties inoculated with the two stronger isolates, though stunting, delay in heading and a reduction in the number of tillers were apparent. In the most susceptible varieties, the rate of growth suffered a marked temporary decrease during the early shock phase of infection.Manitou, one of the varieties of common wheat tested in the greenhouse, was also inoculated with one of the virus isolates in a field plot. The yield from plants inoculated at the three-leaf stage was 64% less than that from uninfected plants. There was a reduction of 40% in yield from plants inoculated when each plant had four to five tillers and the average height was 20.3 cm. Stunting and reduction in the number of tillers and size of heads were apparent in mature plants inoculated at the three-leaf stage. The only symptom on plants inoculated when tillers had developed was a slight yellowing of the leaf tips, first noticeable about 18 days after inoculation.