| Variance analysis and correlation analysis were used to studies on seed health, seed vigor and their relation in 18 species of sweet corn (Zea mays L. saccharata Sturt) collected from Northwest China, North China, South China, Central China and East China. Efficient methods and systems for seed vigor evaluation of sweet corn were established. At the same time, efficient methods of sweet corn seed vigor improvement and their mechanisms were investigated. Research results were showed as follows:1. The research into seed health showed that sugar enhanced corn "Lutian9", "Xixingtianl", "jingketian116" and super sweet corn "Chaotian2000" were more healthy than sugar enhanced corn "Jingketian115" and super sweet corn "Green superman", "Huatianl", "Mitian8". The number of fungi on seed surfaces and percentage of internally infected seeds of former four species was 0.2 cfu per seed ~ 6.7 cfu per seed and 8.5%~51.3%, and later four ones 118.0 cfu per seed - 320.7 cfu per seed and 98.0%~ 100.0%, respectively. Significant differences existed among species type. Sugar enhanced corn (The number of fungi on seed surfaces 29.9 cfu per seed and percentage of internally infected seeds 62.0%) were less infected than super sweet corn (86.2 cfu per seed and 79.2%, respectively) . There were also significant differences among five locations. Samples from Northwest China (0.6 cfu per seed and 14.3%, respectively) were least infected while those from Central China(135.2 cfu per seed and 95.9%, respectively) more infected. Different methods of seed health testing had an effect on experiment results. More fungi were deteced from PDA than from blotter, such as Aspergillus, Geotrichum, Chaetominm and so on. So, PDA testing could refect seed health status more efficiently. Health status of seed surfaces had no significant impact on seed vigor while fungi inside seeds had great impact. Further research showed that Fusariwn was the most frequently isolated fungus whose incidence on seed sufaces was 66.1% and 67.4% in seeds and had the most drastic impact on seedling emergence. Percentage of Fusarium in seeds had a significant negative correlation with seedling emergence rate.2. The research into seed vigor showed that seed vigor of sugar enhanced corn "Tiandan8", "Tiandan10", "Sutian8" and super sweet corn "Mitian8" were significantly lower than those of sugar enhanced corn "Lutian9", "Jingketian116" and super sweet corn "Chaotian2000", "Yangtian1". Seedling emergence rate of former four species was 38.9%~47.2% and later four ones 71.3%~80.6%. Correlation analysis showed that there was a significant correlation between seedling emergence rate and dehydrogenase activity, electrical conductivity, the content of soluble sugar, the content of microscale formaldehyde, or germination rate through paper while there was no significant correlation between seedling emergence rate and standard germination rate or germination rate of cold resistance. Furthermore, there was also a significant correlation between seedling emergence velocity and electrical conductivity, the content of soluble sugar or dehydrogenase activity. The three vigor indexes were the best ones evaluating seed vigor.3. At the same time, methods of sweet corn seed vigor improvement were investigated. Results suggested that sand priming significantly enhanced seed vigor of super sweet corn. After primed, seedling emerged earlier for about 4d and seedling emergence rate was promoted by 27.5%~36.5%. Electrical conductivity was deseased by 27.2%~43.3%. On the twelfth days since sowed, seedling was heightened by 16.1%~29.0 %, seedling fresh weight was promoted by 22.2%~39.8%, SOD and CAT activities were inseased by 5.9%~10.5% and 7.8%~21.1%, respectively. There was no significant difference between single treatment and combined one. Sand priming (riboflavin) played most significant role. However, there was no significant difference between it and sand priming(water) . Given simpleness and economy, the later was best.4. Further reseach into seed vigor mechanisms on...
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