Study On Difference Of Mildew Characteristics Of Different Soybean Genotypes

Eighteen soybean materials with larger differences in agronomic traits were selected in this experiment. This research compared the difference of mildew of eighteen materials by imitating high humidity environment to impel seed mildew at harvest time. At the same time, this test studied the correlations between the resistance to mildew of plant and agronomic traits and components of seed. In contrast with treatment which was not moisturized, this test also studied the effects of mildew on yield and quality of soybean. The main research results were showed as follows:1. After seed mildew, it was transmutative and plicated with different degree, and emited moldy stench. At the beginning of the mildew, coats of some seeds were red or white. The symptom of most seeds with mildew was black or black green mildew spot. The coats of few seeds were covered white mildew.2. After eighteen different soybean genotypes mildew, range of the rate of mildewed seeds was from3.95%to96.25%. There was no immune material to mildew in this experiment. The differences of mildew indexs of seed of eighteen materials were significant or extremely significant. According to the division standard of the resistance to mildew, C103and2162were high resistance, mildew indexs of seed were1.61and2.50respectively; D49and A3were resistant, mildew indexs of seed were12.04and12.27respectively;2077,2084and D48were moderate resistance, mildew indexs of seed of which were25.17,26.79and28.07respectively; six materials, including2080, Gong378-1and D22, were susceptible, mildew indexs of seed of which were32.90～49.82, At present, Gongxuanl (E72) and Nandoul2(D16) that widespread used in the relay strip intercropping soybean’s production belonged to susceptibility, mildew indexs of seed of which were32.90and41.75respectively; five materials were high susceptibility, including D15, E60, E70, A13and D1141, mildew indexs of seed of that were51.13～58.79. The linear regression relation between the rate of mildewed seeds (X) and mildew index of seed (Y) was extremely significant, the equation was Y=59.172X-3.4379, R2=0.9601. 3. The rates of high mildew level that of all seeds gradually reduced with the increase of resistance to mildew of soybean, while proportion of the zero grade seed gradually risen, thus, it got lower mildew index of seed. According to the layered method of0～20,20～40,40～50, over50cm, the vertical distributions of mildewed seeds with all materials were irregular, it presented the respective characteristics.4. Seed and pod mildew had the following relations. The pod was easy to mildew, but the seed wasn’t easy; The pod and seed were all easy to mould; The pod and seed were not easy to mildew; The pod was not easy to mould relatively, but the seed was easy to mildew. Correlation analysis showed that the correlations between rate of mildewed seeds, mildew index of seed and rate of mildewed pods, mildew index of pod were insignificant.5. The mildew index of seed and plant height, stem nods number, pod number per plant, seed number per plant, and seed length/seed width were significant or extremely significant negative correlation. The mildew index of seed was significant positive correlated with100-seed weight, pod wall weight, legume weight, relative content of fat, absolute content of fat and soluble sugar weight per seed. The seed coats of two materials that had high resistance to mildew and two materials that were resistant to mildew were all deep colour, three of which were black, the other was brown, and the hilums of the materials were also all deep colour, there of them were black, one was puce, however, seed coats of the fourteen materials which were easy to mildew were all yellow (except E70, it was green), most hilums of them were also light brown or puce.6. Mildew significantly reduced the yield per plant of soybean that didn’t include mouldy seeds. The yield per plant of eighteen soybean materials decreased range from23.14%to96.55%. The correlation analysis showed rate of mildewed seeds, mildew index of seed and yield loss were highly significant positive correlation, the related coefficients were0.996and0.982; The equation which rate of mildewed seeds (X1) forecasted yield loss (Y1) was Y1=0.8208X1+0.1805, R2=0.9921, the linear regression equation between the mildew index of seed (X2) and yield loss (Y2) was Y2=0.0134X2+0.2451, R2=0.9643. 7. Mildew significantly reduced protein content, fat content and soluble sugar content in seed. After mildew, the protein weight per seed was significantly reduced for materials, but decrease of materials had big difference, the reduced range was from4.57%to19.52%, the average absolute content of protein of materials decreased13.17%; With the increase of mildew grade, the average absolute content of protein of materials was decreased, that of different mildew grades showed as zero grade> one grade> two grade> three grade> five grade> four grade. After mildew, the absolute content of fat was reduced for materials, the decreased range was from0.04%to17.38%, the average absolute content of fat of materials decreased9.15%; With the increase of mildew grade, the fat content of seed was no obvious regularity among materials. After mildew, the absolute content of soluble sugar was significantly reduced for materials, the decreased range was from41.55%to64.74%, the average absolute content of soluble sugar of materials decreased52.31%; With the increase of mildew grade, the average absolute content of soluble sugar of materials was decreased, that of different grades showed as zero grade> one grade> two grade> four grade> three grade> five grade.