Fresh corn refers to corn that is picked at the milk ripe stage and used for cooking and eating. Because its use and eating method are similar to vegetables, it is also called vegetable corn, and it can also be processed into canned food and processed food frozen food with various flavors, so it is also called canned corn. Strong seasonality, relatively short growth period, large output and high economic benefits have developed rapidly in recent years. It mainly includes sweet corn (fruit corn) and waxy corn. Sweet corn, named after the high sugar content in milk, is a subspecies of corn. It originated in the American continent, and it is the general name of a kind of corn produced by genetic mutation and long-term separation and breeding of ordinary corn. Waxy corn, also known as sticky corn, is named because its dry grain incision is waxy. Waxy corn originated in China and has a long planting history. According to Zeng's argument (1987), waxy corn is a new type of corn produced by genetic mutation and artificial selection after cultivated corn was introduced into China. ?

In recent years, the grain production is relatively surplus, and it is urgent to adjust the planting structure. The growth period of fresh corn is 70 ~ 100 days, and the yield is north of the Yellow River. Because it integrates color, fragrance and taste, it is favored by consumers. Planting fresh corn has the advantages of less investment, quick effect and high income, especially the implementation of pollution-free planting and cultivation can increase production, improve quality, improve commodities and increase economic benefits, which is a good way for farmers to increase production and income.

Sweet corn (Zea mays L. saccharata sturt) carries recessive mutant genes that can significantly increase the sugar content in grains, so it has different genetic types, including common sweet corn, super sweet corn and fortified sweet corn.

(1) Common sweet corn: It has a single recessive sweet gene (sul). The total sugar content of the seeds of homozygous sul sweet corn at milk maturity is generally 8% ~ 1 1%, which is usually more than twice that of ordinary corn, of which sucrose content accounts for 2/3 and reducing sugar content is 1/3, which are 3 times and 2 times that of ordinary corn respectively. In addition, the content of water-soluble polysaccharide in seeds is extremely high, reaching 25% of 1000-grain weight. Therefore, this kind of corn not only has a certain sweetness, but also has a unique waxy taste, good edible flavor and is easily absorbed by the human body. However, usually, after picking 1 ~2 days, some sugar will be quickly converted into starch, and the sweetness will be reduced. Mature grains are dry and translucent.

(2) Super sweet corn: sweet corn with single recessive gene sh2 (shrinkage 2), or bt (brittleness), or bt2, etc. Its main feature is that the sugar content in the grain is extremely high, most of which is sucrose, and the mature grain is generally opaque. The advantage of super sweet corn is that the sweetness is significantly increased. The total sugar content in grains at milk maturity is generally 25%~35%, which is more than 10 times higher than that of ordinary sweet corn. The conversion rate of sugar into starch is slower than that of ordinary sweet corn, so the harvest period and storage period are relatively prolonged, generally reaching about 1 week. But the seed coat is thick, the softness is poor and the flavor is poor. Because the seeds are dry, the germination rate of seeds is low and the viability of seedlings is weak.

(3) Fortified sweet corn: This kind of corn not only has sul sweet gene, but also has a sweet modified gene se, which is essentially a double recessive genotype. The sugar content in the grain at milk maturity can reach more than 30%, which has the advantages of common sweet corn and super sweet corn, high sugar content and good flavor. At the same time, the harvest period is long, and the sugar content is still 15 45 days after spinning. In addition, the germination rate and seedling growth of this kind of corn seeds are equivalent to those of ordinary sweet corn and obviously superior to super sweet corn.