Abstract
1. This paper deals with the results on seed treatment of Astragalus sinicus L. with sulphuric acid solution for destroying the sclerotia of Sclerotinia trifoliorum Eriks. contaminating the seeds.
2. Commercial seeds of A. sinicus in Japan have contained sclerotia of S. trifoliorum from 90 to 350 or more in number per 100ml of the seeds.
3. The larger the sclerotia, either scratched with sand or not, the greater the germination by apothecia, while the smaller sclerotia decayed more easily during germination.
4. The minimum volume of acid solution for treating seeds was about 60 per cent of the volume of the seeds. The seeds treated with 7 or 8 per cent solution of sulphuric acid for 3.5 and 4.0 hours gave a higher percentage and greater energy of seed germination than those of untreated seeds. Moreover almost all the sclerotia treated decayed and degenerated, and did not germinate by apothecia, while with untreated sclerotia 95-97 per cent of the sclerotia used germinated. In field experiments, the treated seed plots were free from disease at all, but the untreated seed plots were severely diseased. Preliminary experiments showed that the yield from treated seeds was as much as 3 times greater than that of untreated seeds.
5. From above data, we should expect good results for destroying the sclerotia mixed with the seeds of A. sinicus, by seed treating for 3.5 to 4 hours with 7 or 8 per cent solutions of sulphuric acid.
