Studies on Resistance of Wheat Varieties to Scab (Gibberella zeae (Schw.) Petch.) : VII. Scab infection of rachis of wheat head by the improved method of inoculation and varietal differences in resistance

Abstract

The previous report (vid. Proc. Crop Sci. Japan. Vol.35: 3.4) revealed that any floret of a wheat head can be infected by the improved method of inoculation, though no agreement was observed between the spread of scab lesion and the degree of damage in the field. In this study, it was attempted to inoculate scab onto the rachis, using several varieties resistant and susceptible to scab, to know whether or not the degree of lesion by the artificial inoculation reflects the varietal response. The rachis could be inoculated with success by the following way. 1. Two little holes are pricked with a pin in a segment of a rachis from which all the spikelets had been removed. 2. The treated segment is inoculated with scab and wound with a piece (7×20 mm) of a boiled spinach leaf. 3. The inoculated rachis is wrapped with wrap film all over the length. 4. The treated plant is kept at 20∼25°C. In this case it must be noted that the number of segment in a rachis was limited to 12∼13 and only the terminal segment was inoculated, for the convenience of comparison of varietal responses. Negative results were obtained as in the case of inoculation onto head, that is, the degree of lesion by the artificial inoculation was not always in parallel with the degree of damage in natural conditions.