| Soybean mosaic virus (SMV) occurs in soybean worldwide and causes significant yield loss and seed quality reduction. The virus is seed-transmitted and also readily sap-and aphid-transmissible, so easily cause prevalence. Because SMV can't be prevented by chemicals, many resistance cultivars have developed and used in soybean production. But , the cultivars indraught from other regions can not resistant to their own region's virus in fact. It is because there are different SMV strains in different regions, and cultivar's resistance extent are not the same;also, SMV's infection ranges are not the same. Based on these reasons, when we choose the resistance cultivars, we must investigate the region's prevalence SMV strains and then study resistance identification. This is an economic and efficiency work.To study our province's soybean cultivar's resistance, we choosed nine soybean cultivars mainly planted in Hebei province, including high protein content cultivars: Jidou 12, Jidou 7;high oil content cultivars: Jihuang 13, nf37, nf58;both high content of protein and oil cultivars: Jidoul5, Jian15;and cultivars without fishy smell: Wuxing 1, Wuxing 2, manually rub inoculation with six strains of SMV, including Sc-8, Sc-11,3238 separated and purification from Hebei province, Sc-3 from Huanghuai region, Sa from Jiangsu, N3 from Northeast. The results showed that: The high protein content cultivar Jidou 12 is an ideal resistance cultivar, which exhibits the first type of resistance level to six strains;Wuxing 1 breeded in 2001 exhibits the zero type of resistance level to five in six strains;and Wuxing 2 also a good resistant sources to SMV. But the high oil content cultivars all exhibit lower resistance to six strains. So we believed Wuxing 1, Jidou 12 and Wuxing 2 are three good resistant sources to SMV.We selected a virus resistant combination on the basis of identification above. We found that jidou 7 is sensitive to Sc-8 of SMV and resistant to N3 strain of SMV .Electron microscope technology was used to reveal the mechanism of soybean how to resist the virus infecting. In our research, a series of cytopathic effects were found in jidou 7 after infected by Sc-8 and N3 strans. After jidou 7 was inoculated with virus, the leaves were taken at different time to get the ultrathin sections observed under transmission electron microscope. The cytology changes after the virus infecting in incompatible combination are: at the early stage (inoculated 8 to 12 hours), the structure and shape of chloroplasts and nuclei had a little change;at the later stage (inoculated 72 hours), cell nucleus agglutinated and degradation, the membrane of nuclei and chloroplasts disappeared. Mitochondriadegradation only have two layer of membrane structure. There are only a few viruses observed in the cells , and the pinwheels were not found in cytoplasm. These results indicated that the virus have been restrained in incompatible combination. Duiring the course, chloroplasts and nuclei are the first changed organes, but mitochondria are the last degradated organ. These showed some characters of programmed cell death. In compatible combination the cytology symptoms changed 10 hours later than the incompatible combination . we found pinwheel inclusion in cytoplasm at 5 days after inoculated. Otherwise, the starches synthesized in all the time before cell breakdown. In the cytoplasm the number of mitochondria increased abnormaly, perhaps for the sake of energy anabolism for virus multiplication. In addition, we proved that virus RNA begin to transport with long distance at 12 hours after inoculation.
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