Health Testing Of Soybean Seed Purple Stain And Effect Of Seed Treatment With Fungicides

By means of dry detection, microscopy, TTCH, HPLC, ESEM-EDAX, segregated-planting and several agrochemical testing, this study researched the location of pathogen in soybean seed, the effect of the pathogen to soybean seed and the seed-transmitted action, and screened several fungicides to control the disease through seed treating.1. Cercospora kikuchii could be detected on and in the surface of soybean seed, especially between the epidermis and middle, but not in embryo.2. With the level of seed-infected increased, the vigor of soybean seed decreased obviously, and percentage of vigorous soybean seeds was positively correlated with the OD of TTCH in linear relationship of Y=0.010IX + 0.9812, and the corresponding coefficients of determination was 0.9294. Data of HPLC indicate that cercosporin was not extreated from embryo but coat of soybean seed, and with the level of seed-infected increased, cercosporin's content also grew rapidily to 65 and 294μg in each each gram seed coat of soybean in level 3 and 4 respectivly. 10 kind of chemical elements were detected by ESEM-EDAX from tested seeds, but only C, O, K, Ca was found in the infected site on soybean surface, and C, O, K, Mg in that of embryo; the Wt% and At% of another chemical elements decreased below the zero line in test; the content of C, K in infected seed decreased, and O increased compared with healthy soybean seed. Conclued that with the level of seed-infected grow, the content of cercosopoin increased and seed vigor of infected soybean by pathogen decreased; and after infected, the content and variety of chemical elements of soybean seed changed.3. Results about the ransmittion conducut of cercospora kikuchii from seed to plant and new seed indicated that germination energy and germination rate of the combination seeds are 64.50% and 91.25%, respectively. During the grow life of combination soybean seeds, the typical affected symptom were observed on cotyledon, radicel, stem, leaf, pod and seed. And pathogen was tested in some affected tissues. The percentage of diseased seed after harvest is 54.8%, as 169% as control's, and the pathogen in the soil was tested from where the diseased plant was harvested., moreover, percentage of pathogen tested in soil is 21.6%, higher obviously than control., concluded that the disease may be transmitted by seed.4. Carbendazim, prochloraz, bymexazol, and thiram were screened from 7 tested fungicides to be used in seed treating, their EC50 is 0.0612,8.6284,11.4859,13.6347μg/ml, When each 100kg soybean seed was treated, 100-500,250-500,280-350,100-2000g effected ingredient of the four fungicides respectively was needed, which made their control effect is good and safty to seedling germination and growing.