| Soybean mosaic virus (SMV) is one of the most destructive diseases. It has been found in all soybean production regions in China. It causes loss of yield and decrease of quality. The inheritance of resistance in infection (RI) to SMV in soybean has been widely studied. The results showed that the resistance to different SMV strains is controlled by a dominant gene respectively. Some molecular markers of resistance genes have been screened out. Many resistance cultivars have been developed and used in soybean production-Preliminary study discovered that there was difference not only resistance in infection to SMV between different cultivars, but also in diseased rate, severity and rate of disease development. A preliminary study on resistance in development (RD) has been performed by Dongfang Yang. Based on them, aim of this study was to reveal performances of two kinks of resistance to soybean mosaic virus in soybean; to evaluate resistance germplasm; to analyze the inheritance mechanism of RI., RD and symptom reaction to soybean mosaic virus; to research the breeding method of cultivars with RI or RD to SMV.A sample of 67 soybean cultivars was evaluated for their infection type (IT) . diseased rate (I), diseased rank (S), latent period (LP) and rate of disease development (R) in order to study the performances of two kinks of resistance to soybean mosaic virus in soybean. The results showed that the resistance in infection and resistance in development of soybean to SMV are different resistance mechanism. The performances of the four resistance components of cultivars were significantly different between cultivars. Some of the cultivars such as Kefen 1 were resistant to infection, others such as Lishui zhongzihuangdou, Peixiantianedan, Youbian30 could be infected by four SMV strains, Sa, SC8, Nl and N3, but their I, S, and R were lower and LP longer than those of most of the cultivars. These results demonstrated there existence of two kinds of resistance to SMV in soybeans. In fact, some soybean cultivars such as AGS19 and Lishuizhongzihuangdou, which previously were identified as resistant in infection to SMV, were susceptible to infection, but resistant in development. The resistance to SMV in Pixianchadou and Huaiyinqiuheidou might be either resistance in infection to Sa or resistance in development to other strains.Based on four resistant components, cluster analysis of 63 soybean cultivars was conducted. Result showed that the cultivars could be divided into 6 resistance types, namely resistance in infection (immune), highly resistance, moderately resistance, moderate, moderately susceptibility and highly susceptibility .Besides immune type, discrimination function formulas of 5 resistant types of soybean cultivars were established. A syntheticdisease index (SDI) by mean of diseased rate, disease rank and days from inoculation to maximum disease index was given. Result of cluster analysis conformed to result of synthetic disease index classification.The ultrastructural alteration of three kinds of soybean cultivars, namely the resistance in infection, resistance in development and highly susceptibility cultivars infected with Sa was studied with transmission electron microscope. More thread-like SMV particles, Cylinderical inclusion bodies and Pinwheel inclusion bodies and ultrastructural alteration such as the incomplateness of the choloroplast membrane extena, the looseness of the grana, the swell and disintegration of some chloroplast were found in leaves cell of highly susceptibility cultivars than in that of cultivars with resistance in development. No obvious alteration took place in cultivars with resistance in infection.Ten crosses between materials with RI and those with RD and among materials with different degree of RD were used to reveal the inheritance of resistances. The results showed that the resistance in infection and that resistance in development were controlled by different genetics systems. The former was conditioned by a single dominant gene, while the latter was controlled by one additive... |
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