| Sweet corn is popular among consumers because of its excellent taste quality,but its low seed germination rate,poor seedling growth and other problems seriously hinder the promotion and application of sweet corn.Therefore,how to improve the seed vigor of sweet corn is the main problem to be solved urgently in sweet corn industry.In this study,the popular varieties"Zhetian11"（ZT11）,"Zhengtian68"（ZT68）,"Zhetian2088"（ZT2088）and"Lvsechaoren"（LSCR）in Zhejiang Province,were used as test materials.From 2021 to 2022,alginic acid soaking experiments including the indoor and field germination test were conducted in Zhejiang A&F University Pingshan experimental base to determine the effect of alginic acid treatment on seed vigor,field emergence rate of sweet corn,and the optimal concentration of alginic acid soaking.On this basis,the antioxidant enzyme activity,malondialdehyde（MDA）content and the activity of key enzymes of carbohydrate metabolism and related gene expression were further analyzed.Based on the results of research above,the seed coating agent of sweet corn with alginic acid was developed and applied to the production practice of sweet corn.The regulation mechanism of alginic acid was preliminarily amplified,so as to provide technical support for the production of sweet corn.The main results are listed as follows:1.Seed soaking with alginic acid significantly improves the seed vigor of sweet corn.With the increase of alginic acid soaking concentration,the seed vigor of sweet corn tended to increase firstly and then decrease.The optimal soaking concentration was 4×10-5g/L.However,there was no significant difference between the treatments in the’LSCR’.Compared with the seed vigor of CK1and CK2,the germination potential,germination rate,germination index,and vigor index increased by 10.2-26.3%and 4.1-16.6%,2.2-11.6%and 2.5-12.1%,4.5-18.3%and 1.5-13.9%,18.7-57.6%and10.9-42.5%,respectively.Furthermore,compared with the seedling quality,seedling height and root length under the alginic acid soaking treatment at 4×10-5g/L were increased by 31.3-127.9%and1.9-101.4%,30.7-47.4%and 20.5-35.4%,respectively.Seed soaking with alginic acid significantly increased the field emergence rate of sweet corn seeds.Compared with CK1 and CK2,the field emergence rate were increased by 13.1-18.8%and 11.2-17.7%after seed soaking with alginic acid at4×10-5g/L.2.Seed soaking with alginic acid significantly improved the antioxidant enzyme activity and reduced the MDA content of sweet corn seeds.Superoxide dismutase（SOD）,catalase（CAT）,peroxidase（POD）,and ascorbate peroxidase（APX）activities were increased by 12.5-31.5%and17.7-35.8%,22.5-118.1%and 8.5-126.8%,17.2-40.9%and 8.5-18.8%,27.6-53.3%and 4.4-29.1%,respectively,and the MDA content were reduced by 17.4-39.7%and 12.0-29.8%under alginic acid soaking treatment at 4×10-5g/L compared with CK1 and CK2.Moreover,the expression of antioxidant enzyme genes was significantly up-regulated after alginic acid soaking treatment.Compared with CK1 and CK2,the expression levels of ZmAPX1,ZmMSD3.4,ZmCAT1 and ZmPOD5under alginic acid soaking treatment at 4×10-5g/L were increased by 17.8-41.7%and 19.7-71.3%,33.6-76.1%and 14.2-56.5%,18.8-62.5%and 8.4-40.7%,25.5-67.4%and 13.9-32.4%,respectively.3.Seed soaking with alginic acid significantly improved the carbohydrate metabolism activity of sweet corn seeds.The activity ofα-amylase（α-AMY）in seeds soaked with 4×10-5g/L alginic acid was significantly increased by 51.3-486.4%and 25.5-106.6%compared with CK1 and CK2.In addition,the key enzymes of respiratory pathway were increased gradually in the early stage of seed imbibition,the maximum value was recorded at 24 h.Compared with CK1 and CK2,the activities of hexokinase（HK）,pyruvate kinase（PK）and glucose-6-phosphate dehydrogenase（G6PD）were increased by 25.5-44.3%and 9.0-31.0%,23.6-39.0%and 16.2-38.0%,14.4-24.2%and 10.0-15.8%,respectively,and citrate synthase（CS）was increased by 28.8-68.5%and 1.2-10.0%（except for‘ZT2088’）.Further analysis of the key enzyme gene expression related to the respiratory metabolism,compared with CK1 and CK2,the expression of ZmHK1,ZmPK2,ZmG6PD2 and ZmCS1 genes in seeds soaked with alginic acid at 4×10-5g/L were increased by 49.4-66.4%and 23.3-34.4%,43.7-126.0%and 18.7-30.4%,30.7-54.8%and 9.2-34.1%,119.6-172.6%and 9.3-93.3%,respectively.4.Based on the research of alginic acid soaking,seed coating agent was developed with alginic acid as the main component.Seed coating could effectively improve seed vigor of sweet corn.Coating agent 3（SC3）with the main components of alginic acid+manganese sulfate+6-BA+imidacloprid had the best effect.Compared with the uncoated treatment,the germination rate,germination potential,germination index,vigor index,and field emergence rate were increased by16.2-38.4%,20.8-256%,19.1-31.3%,53.9-62.6%and 12.0-16.1%,respectively.Furthermore,SC3treatment can significantly increase the antioxidant enzyme activity in sweet corn and increase the expression of antioxidant enzyme-related genes,compared with uncoated treatment,the APX,SOD,CAT,and POD activities were increased by 41.0-42.0%,29.5-33.2%,38.5-137.3%,8.6-43.8%,respectively.The expression levels of ZmAPX1,ZmMSD3.4,ZmCAT1,and ZmPOD5 were increased by 55.6-74.2%,35.8-42.5%,57.9-74.7%,21.8-31.3%,respectively.In summary,the expression of antioxidant and carbohydrate metabolism genes in sweet corn seeds was induced by alginic acid treatment（soaking or coating）before sowing.Improving the activity of antioxidant enzymes and carbohydrate metabolism enzymes in seeds,increasing the stress resistance and energy supply capacity of seeds,and promoting seed germination and seedling establishment. |
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