Abstract
Necrotic symptom occurs on broad bean by local and systemic infection caused by alfalfa mosaic virus. Some factors concerning the occurence of this necrotic symptom were observed.
The results are presented in this paper.
1) Occurence of necrotic symptom of inoculated leaf is closely associated with the degree of multiplication of the virus. In an inoculated young leaf which the virus increases more rapidly than in an old lower leaf, necrotic symptom appears more sever.
2) Wherever inoculation is done on any part (leaf, leaf-petiole and stem), if the virus multiplies sufficiently there, necrosis develops always almost concurrently on systemically infected apical leaves. When lower leaves and lower part of stem were inoculated, necrosis of apical leaf is difficult to appear.
3) The virus concentration in the inoculum influences remarkably the development of necrosis on apical leaves. When dense inoculum was used, the virus multiplies much more in inoculated leaf and necrosis of apical leaf appears in higher rate.
4) Appearence of necrosis of apical leaf relates with the growth stage of upper leaves. Leaves which exhibit necrosis due to systemic infection are limited to unexpanded apical leaves smaller than about 24mm in length at the time of inoculation.
