Post by canadamike on Mar 10, 2010 1:17:52 GMT -5
Here are 2 interesting explanations of different sugary genes for the people who are having problems to understand the language of many posts here. I took one , from the University of VERMONT vegetable and berry pages the other from the Ontario ministry of agriculture:
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SWEET CORN GENOTYPES
Vern Grubinger
Vegetable and Berry Specialist
University of Vermont Extension
Sweet corn breeders have their work cut out for them. Of the thousands of crosses they make in the field each year, only a few ever result in a commercial variety. Not only that, there are more and more genes being used to provide corn with different degrees of sweetness, flavor, and eating quality.
Many growers are already familiar with the three main genetic groups, or genotypes, of sweet corn: sugary (SU), sugar enhanced (SE) and supersweet or shrunken (SH2). What’s new is the development of varieties that contain different combinations of these genes.
At the recent New England Vegetable and Berry Conference in Manchester, New Hampshire, Blake Myers of Siegers Seed Company gave an excellent overview of the genetics of sweet corn, and what that means for growers. I’ve based this article on the information he provided.
Let’s start at the beginning. For the first 4,000 years or so that people grew corn, there wasn’t any ‘sweet corn.’ Instead, field corn (dent corn) was harvested when it was still immature, which wasn’t quite as bad as eating ‘cow corn.’ Then, along came the ‘SU’ sugary gene that provided more sugar than field corn. Sweet corn was first documented in the 1770’s in Pennsylvania, although native Americans had probably cultivated it prior to that. Sweet corn made its first appearance in seed catalogs in the 1820’s.
Sweet corn had primarily white kernels until 1902 when Golden Bantam, a yellow variety, was developed. Then, crosses were made that resulted in bi-color varieties. While the color of sweet corn kernels is important with regard to consumer preference, it doe not have anything to do with flavor.
SU varieties have modest amounts of sugar in their kernels, and they tend to have decent corn flavor. But, their conversion of sugar to starch is rapid, so they have a narrow harvest window before flavor deteriorates. They tend to good plant vigor. To avoid cross-pollination and poor quality, SU varieties must be isolated from field corn and popcorn. They must also be isolated from the supersweet group.
In the mid-1900’s, some very important new sweet corn genes were developed: ‘SH2’ shrunken gene and the ‘SE’ sugary enhanced gene.
The SH2 gene greatly boosts the amount of sugar in the endosperm (the part of the kernel where energy is stored for later use by the developing embryo), and that’s why SH2 varieties are often called ‘supersweets’. The seeds of these varieties have less starch in them, so they appear shriveled and weigh less than other sweet corn seeds. (Because of the shriveled characteristic of the seed, they are sometimes referred to as shrunken 2 or just SH2.) They can be a challenge to grow, especially in the north, because they need warmer soil for good germination. The SH2 gene slows the conversion of simple sugars to starch, so supersweet varieties have a much wider harvest window than other genotypes. SH2 varieties must be isolated or they will become tough and starchy, and they will also ruin SU or SE varieties grown next to them, if the pollen happens to cross.
The SE gene gives varieties improved eating quality over SU varieties by slightly increasing the level and changing the types of sugars in the kernels. SE varieties also have a very tender pericarp (the outer layer of the kernel). The SE gene does not slow the conversion of sugars to starch but the harvest window is slightly longer than with SU varieties because of elevated sugar levels. SE varieties do not require isolation from SU varieties, but they do require isolation from SH2 and field or popcorn.
Some SE varieties are sweeter than others, depending on whether one or both of their parents were sugary enhanced. Varieties that get the SE gene from both their parents are homozygous for that trait, or ‘double SE,’ and all of their kernels have the SE characteristics. Varieties that have just one SE parent are heterozygous, or ‘single SE,’ develop 25% of their kernels with SE traits. Typically a homozygous SE will have better eating quality than a heterozygous SE. For example, Tablesweet™ varieties such as Parfait are homozygous SE with high sugar levels and slightly better holding ability.
Within the SU and SE genotypes, modifier genes are responsible for differences in flavor. A variety can be homozygous or heterozygous for a modifier gene, just like the SE gene. Modifier genes are what allow breeders to develop so many different varieties. They are why it’s possible to have an 80-day, bi-color homozygous SE corn that has better eating quality that another variety that shares those same features.
In recent years new varieties have been developed that have different combinations of the three major genes (and their modifier genes) ‘stacked’ together. The goal of breeders is to put together the best characteristics from SU, SE and SH2 genes.
‘Synergistic’ varieties are heterozygous or homozygous SE, with the addition of some SH2 kernels. Sweet Breeds™ varieties such as Sweet Chorus and Sweet Rhythm have about 25% SH2 kernels, 25% SE kernels and 50% SU kernels. The seed has SU vigor but higher sugars. Triplesweet™ varieties such as Providence have 100% SE kernels, 25% of which also have the SH2 trait. These are like double SE varieties in vigor, but sweeter.
‘Augmented SH2’ varieties are supersweet types that also have the SE trait in all their kernels. Examples include Gourmet Sweet™, Multisweet™ and Xtra-Tender Brand™. These are high in sugars, slow to convert to starch, and tender like an SE. Mirai has all three genotype traits in its kernels: SH2, SE and SU.
In terms of isolation requirements, these newer varieties generally behave as either a SU or SH2, depending on the combination of genes. The table below shows which varieties need to be isolated from one another.
SU AND SE ISOLATION GROUP
Normal sugary (SU)
Sugar enhanced (SE)
Synergistic Mirai
SH2 GROUP
Shrunken ( SH2)
Augmented SH2
Since there are so many sweet corn choices, it makes sense for growers to consult with seed company representatives for help in deciding what varieties will work best for the conditions on their farm, and their customer’s tastes.
------------------------------------------------------------------------------------------------------------
Introduction
There has been a significant increase in the demand for fresh market sweet corn in recent years due to the dramatic improvement in the sugar levels of new sweet corn cultivars (varieties). This is primarily due to the introduction of new "high sugar" cultivars. These higher sugar levels are the result of new genes that improve the corn’s sweetness.
| Top of Page |
Sweetness Genes
Thirteen genes have been found that could eventually improve the sugar levels of sweet corn. The three major genes today that affect the sweetness of corn are:
(1) the "sugary" gene (su):
(2) the "Sugary Enhancer" gene (se); and
(3) the "Supersweet" gene (SH2).
Normal sweet corn cultivars that we have been growing for years contain the sugary "su" gene. These cultivars produce an average amount of sugar but the sugar changes to starch fairly quickly after harvest if their cob temperature isn’t rapidly cooled.
Sugar enhanced corn cultivars contain the sugary enhancer"se" gene. These cultivars produce a higher amount of sugar than "su" types. Cultivars with the "se" gene also convert sugar to starch like normal sweet corn, but they will retain a sweet flavor longer after harvest because they have higher sugar levels to begin with. Cultivars containing the "se" gene tend to have thinner pericarps (skin over each kernel) and therefore must be handled more gently. This thin pericarp means they are more likely to be injured by a mechanical harvester. These cultivars contain the same types of complex sugars and therefore taste similar to normal sweet corn but they are sweeter and more tender.
There are two distinct groups within the cultivars containing the "se" gene. Firstly there are the "Homozygous se" cultivars. They have higher sugar levels in 100% of their kernels. The other group includes cultivars containing the "Heterozygous se" gene. They have higher sugar levels in 25% of their kernels: the other 75% contain the normal su gene with lower sugar level. So "Homozygous se" cultivars are usually sweeter than "Heterozygous se" cultivars.
Supersweet corn cultivars contain the "SH2" gene. These cultivars do not convert sugar to starch readily and therefore stay sweet for a very long time after they reach harvest maturity. This allows more time for growers, wholesalers and retailers to market the corn. Also, since SH2 types retain their sweetness longer in the consumer’s home, it allows the family more time to enjoy their sweet corn. This does not mean "SH2" types can be held indefinitely or that they don’t need rapid cooling after harvest. "SH2" cultivars are still living, breathing and burning up stored sugars. So as maturity advances, they burn up sugars which lowers their sweetness and their kernels develop thicker pericarps (skin), which means that they become more chewy.
Three Major Sweetness Genes Gene Type
% Sugar
su
Normal 9-16
se
Sugar enhanced heterozygous 25% se 14-22
Sugar enhanced homozygous 100% se 20-35
SH2
Supersweet 28-44
Source: University of Illinois
Now corn breeders are looking at gene combinations that will get even higher sugar levels. Combinations are also being tested to improve the germination of cultivars containing the SH2 gene.
| Top of Page |
Isolation: by Gene Type or Kernel Colour
Sweet corn is unique. Of all the fruits and vegetables we grow in Ontario, sweet corn is the only one where pollen from another cultivar can affect the quality (sugar level tenderness and kernel color) immediately. In all other crops the effect of pollen would not be apparent until the seed produced by that cross-pollination were grown. As a result, for cultivars of each gene type to reach their full potential, they must be grown in isolation from cultivars in another gene type. In some cases the effect can be very dramatic, with the corn at maturity actually taking on the flavor and texture of field corn.
Isolation is most critical with cultivars that contain the SH2 gene. If they are pollinated by other gene types (su, se, field corn or Indian corn), they will revert to field corn with high starch and low sugar. Cultivars containing the se gene that are pollinated by normal su cultivars don’t revert back to field corn, but their sugar levels will decline to normal su type levels.
All 3 gene types su, se and SH2 have yellow and white cultivars.
Isolation by Kernel Color
All three gene types (su, se and SH2) have yellow, white and bicolor cultivars, and pollen from one color can affect the color of another. This means it is important to isolate plantings not only by gene type, but also by kernel color. Yellow and Indian corn kernel colors are particularly overpowering. Yellow cultivars will make a white cultivar bicolor and will reduce the number of white kernels in a bicolor. Likewise, bicolored cultivars produce some yellow kernels in white cultivars.
Indian corn pollen can also dramatically affect the appearance of all three types (yellow, white and bicolor) by causing black kernels to appear in their cobs.
Cross-pollination is primarily a problem in the outside three or four rows of any planting. Further inside a planting there is so much pollen of the same cultivar that the effect of the unwanted pollen from another gene type is minimal.
Isolation can be attained in different ways:
1. Separate one gene type from another by at least 100 m (350 ft.).
2. Prevailing winds can carry unwanted pollen downwind. One hundred metres may not be enough. It will help to plant the more sensitive gene type upwind to ensure it is not cross-pollinated by another gene type.
3. Schedule plantings so that tasselling times are two weeks apart. This technique prevents cross-pollination without separating the gene types by 100 m.
4. If space is limiting and tasselling times cannot be separated by two weeks, separate one group from another by 15 m. Then treat the four outside rows of the downwind cultivar as buffer rows. The pollen from these four buffer rows will dilute the effect of the pollen from the other gene group upwind. These four buffer rows will be contaminated with foreign pollen and should not be marketed.
| Top of Page |
Improving Germination of High Sugar Cultivars
Emergence of sweet corn plantings are influenced by a number of factors including soil temperature, seed quality, soil moisture, depth of seeding and the gene type of the cultivar. We will look at these factors and their effect on emergence:
1. Soil Temperature
Soil temperature has a dramatic effect on the speed of germination and percentage seed emergence. Most seed companies will identify the cultivars which will tolerate colder soils.
Putting seed in soil that is too cold for germination means that they will lay dormant in the soil. This makes the seed more vulnerable to attack by insects and diseases. A good rule of thumb is that Normal (su) cultivars can tolerate the coolest soil temperatures of between 9-13.0°C (48-55.0°F). Sugar Enhanced (se) cultivars will give better plant stands if soils are in the 13-160°C (55-60.0°F) range. Supersweet (SH2) cultivars generally prefers soils above 15.0°C (58.0°F).
2. Seed Quality
Once seed is damaged it becomes very susceptible to insect and disease attack. It is important to note that se, and particularly SH2 cultivars are fragile and their seed requires gentle handling to prevent it from cracking before or during planting. This means laying the bags of seed down gently rather than throwing them.
3. Soil Moisture
Planting seed into moist soil is essential for germination. Otherwise, the seed will lay dormant. But most importantly planting seed into dry soil will put gaps in your harvest schedule.* The ideal way to ensure moisture with the seed is to have an irrigation system.
4. Depth of Seeding
Understandably an irrigation system is not always possible. As an alternative, some growers try to ensure there is moisture with the seed by planting the seed deeper. Normal "su" and sugar enhanced "se" corns can generally tolerate deeper planting because the seed has more food reserves.
SH2 cultivars have very little food reserves and therefore have trouble reaching the soil surface if seeded too deeply. Where possible, avoid planting SH2 cultivars deeper than 2.5 cm (1 in.). If soil moisture is inadequate, it is best to irrigate the field to encourage rapid emergence rather than planting the seed too deeply.
Summary
Sweet corn cultivars have improved greatly over the past few years and they will continue to get even better.
Many retailers are demanding the high sugar supersweet (SH2) types because they have a much longer shelf life and reduce waste in the produce department. Today 90% of Florida’s sweet corn production is the SH2 type and other American states further north are following Florida’s lead. This high sugar corn is imported into Ontario throughout spring and early summer, giving consumers a surprisingly good product. These new corn cultivars also give the consumer more time to enjoy their sweet corn at home.
Unfortunately, supersweet cultivars are proving to be more of a challenge to grow because of their:
* sensitivity to cold spring soils
* low food reserves in their seed
* fragile seed that cracks easily
Sweet corn should continue to be an expanding market for Ontario producers as consumers learn about the new high sugar sweet corn.
----------------------------------------------------------------------------------------------------------
SWEET CORN GENOTYPES
Vern Grubinger
Vegetable and Berry Specialist
University of Vermont Extension
Sweet corn breeders have their work cut out for them. Of the thousands of crosses they make in the field each year, only a few ever result in a commercial variety. Not only that, there are more and more genes being used to provide corn with different degrees of sweetness, flavor, and eating quality.
Many growers are already familiar with the three main genetic groups, or genotypes, of sweet corn: sugary (SU), sugar enhanced (SE) and supersweet or shrunken (SH2). What’s new is the development of varieties that contain different combinations of these genes.
At the recent New England Vegetable and Berry Conference in Manchester, New Hampshire, Blake Myers of Siegers Seed Company gave an excellent overview of the genetics of sweet corn, and what that means for growers. I’ve based this article on the information he provided.
Let’s start at the beginning. For the first 4,000 years or so that people grew corn, there wasn’t any ‘sweet corn.’ Instead, field corn (dent corn) was harvested when it was still immature, which wasn’t quite as bad as eating ‘cow corn.’ Then, along came the ‘SU’ sugary gene that provided more sugar than field corn. Sweet corn was first documented in the 1770’s in Pennsylvania, although native Americans had probably cultivated it prior to that. Sweet corn made its first appearance in seed catalogs in the 1820’s.
Sweet corn had primarily white kernels until 1902 when Golden Bantam, a yellow variety, was developed. Then, crosses were made that resulted in bi-color varieties. While the color of sweet corn kernels is important with regard to consumer preference, it doe not have anything to do with flavor.
SU varieties have modest amounts of sugar in their kernels, and they tend to have decent corn flavor. But, their conversion of sugar to starch is rapid, so they have a narrow harvest window before flavor deteriorates. They tend to good plant vigor. To avoid cross-pollination and poor quality, SU varieties must be isolated from field corn and popcorn. They must also be isolated from the supersweet group.
In the mid-1900’s, some very important new sweet corn genes were developed: ‘SH2’ shrunken gene and the ‘SE’ sugary enhanced gene.
The SH2 gene greatly boosts the amount of sugar in the endosperm (the part of the kernel where energy is stored for later use by the developing embryo), and that’s why SH2 varieties are often called ‘supersweets’. The seeds of these varieties have less starch in them, so they appear shriveled and weigh less than other sweet corn seeds. (Because of the shriveled characteristic of the seed, they are sometimes referred to as shrunken 2 or just SH2.) They can be a challenge to grow, especially in the north, because they need warmer soil for good germination. The SH2 gene slows the conversion of simple sugars to starch, so supersweet varieties have a much wider harvest window than other genotypes. SH2 varieties must be isolated or they will become tough and starchy, and they will also ruin SU or SE varieties grown next to them, if the pollen happens to cross.
The SE gene gives varieties improved eating quality over SU varieties by slightly increasing the level and changing the types of sugars in the kernels. SE varieties also have a very tender pericarp (the outer layer of the kernel). The SE gene does not slow the conversion of sugars to starch but the harvest window is slightly longer than with SU varieties because of elevated sugar levels. SE varieties do not require isolation from SU varieties, but they do require isolation from SH2 and field or popcorn.
Some SE varieties are sweeter than others, depending on whether one or both of their parents were sugary enhanced. Varieties that get the SE gene from both their parents are homozygous for that trait, or ‘double SE,’ and all of their kernels have the SE characteristics. Varieties that have just one SE parent are heterozygous, or ‘single SE,’ develop 25% of their kernels with SE traits. Typically a homozygous SE will have better eating quality than a heterozygous SE. For example, Tablesweet™ varieties such as Parfait are homozygous SE with high sugar levels and slightly better holding ability.
Within the SU and SE genotypes, modifier genes are responsible for differences in flavor. A variety can be homozygous or heterozygous for a modifier gene, just like the SE gene. Modifier genes are what allow breeders to develop so many different varieties. They are why it’s possible to have an 80-day, bi-color homozygous SE corn that has better eating quality that another variety that shares those same features.
In recent years new varieties have been developed that have different combinations of the three major genes (and their modifier genes) ‘stacked’ together. The goal of breeders is to put together the best characteristics from SU, SE and SH2 genes.
‘Synergistic’ varieties are heterozygous or homozygous SE, with the addition of some SH2 kernels. Sweet Breeds™ varieties such as Sweet Chorus and Sweet Rhythm have about 25% SH2 kernels, 25% SE kernels and 50% SU kernels. The seed has SU vigor but higher sugars. Triplesweet™ varieties such as Providence have 100% SE kernels, 25% of which also have the SH2 trait. These are like double SE varieties in vigor, but sweeter.
‘Augmented SH2’ varieties are supersweet types that also have the SE trait in all their kernels. Examples include Gourmet Sweet™, Multisweet™ and Xtra-Tender Brand™. These are high in sugars, slow to convert to starch, and tender like an SE. Mirai has all three genotype traits in its kernels: SH2, SE and SU.
In terms of isolation requirements, these newer varieties generally behave as either a SU or SH2, depending on the combination of genes. The table below shows which varieties need to be isolated from one another.
SU AND SE ISOLATION GROUP
Normal sugary (SU)
Sugar enhanced (SE)
Synergistic Mirai
SH2 GROUP
Shrunken ( SH2)
Augmented SH2
Since there are so many sweet corn choices, it makes sense for growers to consult with seed company representatives for help in deciding what varieties will work best for the conditions on their farm, and their customer’s tastes.
------------------------------------------------------------------------------------------------------------
Introduction
There has been a significant increase in the demand for fresh market sweet corn in recent years due to the dramatic improvement in the sugar levels of new sweet corn cultivars (varieties). This is primarily due to the introduction of new "high sugar" cultivars. These higher sugar levels are the result of new genes that improve the corn’s sweetness.
| Top of Page |
Sweetness Genes
Thirteen genes have been found that could eventually improve the sugar levels of sweet corn. The three major genes today that affect the sweetness of corn are:
(1) the "sugary" gene (su):
(2) the "Sugary Enhancer" gene (se); and
(3) the "Supersweet" gene (SH2).
Normal sweet corn cultivars that we have been growing for years contain the sugary "su" gene. These cultivars produce an average amount of sugar but the sugar changes to starch fairly quickly after harvest if their cob temperature isn’t rapidly cooled.
Sugar enhanced corn cultivars contain the sugary enhancer"se" gene. These cultivars produce a higher amount of sugar than "su" types. Cultivars with the "se" gene also convert sugar to starch like normal sweet corn, but they will retain a sweet flavor longer after harvest because they have higher sugar levels to begin with. Cultivars containing the "se" gene tend to have thinner pericarps (skin over each kernel) and therefore must be handled more gently. This thin pericarp means they are more likely to be injured by a mechanical harvester. These cultivars contain the same types of complex sugars and therefore taste similar to normal sweet corn but they are sweeter and more tender.
There are two distinct groups within the cultivars containing the "se" gene. Firstly there are the "Homozygous se" cultivars. They have higher sugar levels in 100% of their kernels. The other group includes cultivars containing the "Heterozygous se" gene. They have higher sugar levels in 25% of their kernels: the other 75% contain the normal su gene with lower sugar level. So "Homozygous se" cultivars are usually sweeter than "Heterozygous se" cultivars.
Supersweet corn cultivars contain the "SH2" gene. These cultivars do not convert sugar to starch readily and therefore stay sweet for a very long time after they reach harvest maturity. This allows more time for growers, wholesalers and retailers to market the corn. Also, since SH2 types retain their sweetness longer in the consumer’s home, it allows the family more time to enjoy their sweet corn. This does not mean "SH2" types can be held indefinitely or that they don’t need rapid cooling after harvest. "SH2" cultivars are still living, breathing and burning up stored sugars. So as maturity advances, they burn up sugars which lowers their sweetness and their kernels develop thicker pericarps (skin), which means that they become more chewy.
Three Major Sweetness Genes Gene Type
% Sugar
su
Normal 9-16
se
Sugar enhanced heterozygous 25% se 14-22
Sugar enhanced homozygous 100% se 20-35
SH2
Supersweet 28-44
Source: University of Illinois
Now corn breeders are looking at gene combinations that will get even higher sugar levels. Combinations are also being tested to improve the germination of cultivars containing the SH2 gene.
| Top of Page |
Isolation: by Gene Type or Kernel Colour
Sweet corn is unique. Of all the fruits and vegetables we grow in Ontario, sweet corn is the only one where pollen from another cultivar can affect the quality (sugar level tenderness and kernel color) immediately. In all other crops the effect of pollen would not be apparent until the seed produced by that cross-pollination were grown. As a result, for cultivars of each gene type to reach their full potential, they must be grown in isolation from cultivars in another gene type. In some cases the effect can be very dramatic, with the corn at maturity actually taking on the flavor and texture of field corn.
Isolation is most critical with cultivars that contain the SH2 gene. If they are pollinated by other gene types (su, se, field corn or Indian corn), they will revert to field corn with high starch and low sugar. Cultivars containing the se gene that are pollinated by normal su cultivars don’t revert back to field corn, but their sugar levels will decline to normal su type levels.
All 3 gene types su, se and SH2 have yellow and white cultivars.
Isolation by Kernel Color
All three gene types (su, se and SH2) have yellow, white and bicolor cultivars, and pollen from one color can affect the color of another. This means it is important to isolate plantings not only by gene type, but also by kernel color. Yellow and Indian corn kernel colors are particularly overpowering. Yellow cultivars will make a white cultivar bicolor and will reduce the number of white kernels in a bicolor. Likewise, bicolored cultivars produce some yellow kernels in white cultivars.
Indian corn pollen can also dramatically affect the appearance of all three types (yellow, white and bicolor) by causing black kernels to appear in their cobs.
Cross-pollination is primarily a problem in the outside three or four rows of any planting. Further inside a planting there is so much pollen of the same cultivar that the effect of the unwanted pollen from another gene type is minimal.
Isolation can be attained in different ways:
1. Separate one gene type from another by at least 100 m (350 ft.).
2. Prevailing winds can carry unwanted pollen downwind. One hundred metres may not be enough. It will help to plant the more sensitive gene type upwind to ensure it is not cross-pollinated by another gene type.
3. Schedule plantings so that tasselling times are two weeks apart. This technique prevents cross-pollination without separating the gene types by 100 m.
4. If space is limiting and tasselling times cannot be separated by two weeks, separate one group from another by 15 m. Then treat the four outside rows of the downwind cultivar as buffer rows. The pollen from these four buffer rows will dilute the effect of the pollen from the other gene group upwind. These four buffer rows will be contaminated with foreign pollen and should not be marketed.
| Top of Page |
Improving Germination of High Sugar Cultivars
Emergence of sweet corn plantings are influenced by a number of factors including soil temperature, seed quality, soil moisture, depth of seeding and the gene type of the cultivar. We will look at these factors and their effect on emergence:
1. Soil Temperature
Soil temperature has a dramatic effect on the speed of germination and percentage seed emergence. Most seed companies will identify the cultivars which will tolerate colder soils.
Putting seed in soil that is too cold for germination means that they will lay dormant in the soil. This makes the seed more vulnerable to attack by insects and diseases. A good rule of thumb is that Normal (su) cultivars can tolerate the coolest soil temperatures of between 9-13.0°C (48-55.0°F). Sugar Enhanced (se) cultivars will give better plant stands if soils are in the 13-160°C (55-60.0°F) range. Supersweet (SH2) cultivars generally prefers soils above 15.0°C (58.0°F).
2. Seed Quality
Once seed is damaged it becomes very susceptible to insect and disease attack. It is important to note that se, and particularly SH2 cultivars are fragile and their seed requires gentle handling to prevent it from cracking before or during planting. This means laying the bags of seed down gently rather than throwing them.
3. Soil Moisture
Planting seed into moist soil is essential for germination. Otherwise, the seed will lay dormant. But most importantly planting seed into dry soil will put gaps in your harvest schedule.* The ideal way to ensure moisture with the seed is to have an irrigation system.
4. Depth of Seeding
Understandably an irrigation system is not always possible. As an alternative, some growers try to ensure there is moisture with the seed by planting the seed deeper. Normal "su" and sugar enhanced "se" corns can generally tolerate deeper planting because the seed has more food reserves.
SH2 cultivars have very little food reserves and therefore have trouble reaching the soil surface if seeded too deeply. Where possible, avoid planting SH2 cultivars deeper than 2.5 cm (1 in.). If soil moisture is inadequate, it is best to irrigate the field to encourage rapid emergence rather than planting the seed too deeply.
Summary
Sweet corn cultivars have improved greatly over the past few years and they will continue to get even better.
Many retailers are demanding the high sugar supersweet (SH2) types because they have a much longer shelf life and reduce waste in the produce department. Today 90% of Florida’s sweet corn production is the SH2 type and other American states further north are following Florida’s lead. This high sugar corn is imported into Ontario throughout spring and early summer, giving consumers a surprisingly good product. These new corn cultivars also give the consumer more time to enjoy their sweet corn at home.
Unfortunately, supersweet cultivars are proving to be more of a challenge to grow because of their:
* sensitivity to cold spring soils
* low food reserves in their seed
* fragile seed that cracks easily
Sweet corn should continue to be an expanding market for Ontario producers as consumers learn about the new high sugar sweet corn.