The present paper deals with the results of experiments on a dwarf disease of milk vetch (Astragalus sinicus L). The results obtained are summarized below:-
I An infested plant discolors yellowish green to dull yellow and stunts as a whole and its leaflets become small and narrow. Margin of the leanet is often colored reddish purple. Later on, necrotic lesions develop often on Ieaflet, petiole and stem. Most of flower buds of the severe1y infested plant drop down before blossoming. Slightly infested Plants may bloom but the seeds do not ripe perfectly. In case of severely infested plants, the lower leaves dry up from the margin of leaflets and finally, the whole plant die prematurely.
1. Causal agent of this disease was found to be a virus.
2. 4 species of aphids i.e. Aphis laburni Kaltenbach, A. glycines Matsumnura, Macrosiphum Pelargoni Kaltenbach and Myzus persicae Sulzer were tested for transmissibility of the virus and only the first named species of aphid proved to be a vector.
3. Aphis laburni became infective when it was fed on the diseased plant for 24 hours and the virulent aphid was able to transfer the virus to the healthy plant by feeding for more than 6 hours.
4 The infective aphid was able to transfer the virus through its who1e life.
5. The virus was not transferd to viviparous offsprings from the infective parent aphids.
6. The writer failed to obtain successful transmission by mutilating with the diseased plant juice.
7. The transmission of this virus through the seeds was not determined distinctly.
8. This virus seems to be some what differerent from the red clover mosaic virus or common bean mosaic virus. With regard to its identification further investigation is needed.
II this disease was found to be distributed in the prefectures, Yamagata, Fukushima, Niigata, Nagano and Ibaragi.
