Studies on Resistance of Wheat Varieties to Scab (Gibberclla zeae (Schw.) Petch.). : III Pricking, leaf age, size of vinyl ring and amount of agar medium as factors influencing the scab infection.

Abstract

The inoculation method of scab onto leaf blade, reported by the author, involved the pricking as a pre-treatment and the fixation of vinyl ring containing potato agar medium on the inoculated leaf blade by cellophane tape. In this study, these pre and post-treatments were investigated for their effects on the scab infection. It was found that the damage from the scab infection appeared much faster on the pricked leaves than on the unpricked ones. The leaf age also had some effects on the scab infection; the lesion of the older leaf being larger than that of the younger one, or at least the former being equal to the latter, in each of the culms. In the experiments of leaf blade inoculation, therefor, both the uppermost leaf except the emerging leaf and the one immediately below it, or only the uppermost leaf should be used in order to eliminate the difference in the foliage lesions due to the leaf age. The size of vinyl ring also affected the scab infection. The larger the diameter of the ring, the larger the infected spots. But a number of tests showed that the best ring was the one of 5∼6 mm in diameter because of the eczematous spots from the large ring of 7 mm in diameter. The amount of agar medium, in contrast to the ring size, did not affect the spot appearance, when the rings of same diameters were used. In the field application of this method, a certain type of cellophane tape gave an injurious effect on the sticked surface. Nichiban company's "Cello-tepe" and "Scotch Sumitomo 3M company's "Scotch transparent-tape" are recommended.