Effects of Some Enzyme Inhibitors Added to the Inoculum in Mechanical Inoculation of Soil-Borne Viruses of Wheat and Barley

Experiments were conducted to enhance the infectivity of the juice from diseased leaves in the mechanical inoculation of wheat yellow mosaic virus (WYMV) and barley yellow mosaic virus (BYMV), both of which are rather difficult in causing infection by mechanical inoculation, (1) Increased infectivity was observed when diseased leaves were ground with KCN, Na-DIECA or Azide, at the concentrations of 10-3M in phosphate buffer, and used for the mechanical inoculation.(2) The effects of these enzyme inhibitors differed according to the age of the diseased leaves, being more conspicuous in the lower leaves than in the upper ones. Difference was also observed, according to the season in which inoculations were made, i.e. the effect was more conspicuous when the infection by mechanical inoculation was more difficult.(3) When diseased leaves were ground with 10-3M pyrocatechol or hydroquinone as substrate, the infectivity decreased in WYMV, and no infection was caused in BYMV.(4) Polyphenol oxidase activity was confirmed in the juice from WYMV infected leaves. This activity was lost when the leaves were ground with Na-DlECA in phosphate buffer.(5) From these results, it is supposed that the usual low infectivity in mechanical inoculation of WYMV and BYMV is caused in part by the action of polyphenol oxidase.