Cross protection effects between strains of soybean mosaic virus

Eleven strains of soybean mosaic virus(SMV) from different regions were used to study effects on cross protection by different challenge time and inoculation treatments,to compare difference of the cross protection between strains,and to analyze effects of cross protection on some characteristics of soybean cultivar.The results showed that different challenge inoculation time after protection inoculation clearly affected cross protection.Protection rate was higher in seven days than that in three,five,nine and eleven days.Cross protection was also affected by different inoculation treatments.Cross protection was observed when cultivars inoculated by one strain after another,whereas no protection appeared when cultivars were inoculated with mixture of two strains,or each unifoliolate was inoculated by different strains respectively.Cross protection varied in degree when strains with different symptom were used as protection inoculums.Mosaic strain exhibited much better protection effect than necrosis strain.Cross protection decreased effect of SMV on leaf area and root dry weight.The effects of cross protection on plant height,chlorophyll content and nodule fresh weight depended on different soybean cultivars and SMV strains.