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Consider details when selecting soybean varieties

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HUTCHINSON -- Variety selection is one of the most important management decision producers make. Utilize the University of Minnesota Varietal Trials Soybean Performance Report -- at http://www.maes.umn.edu/10varietaltrials/ -- and information from seed companies and your on-farm trials to select high-yielding, well-adapted varieties.

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Consider the following characteristics: yield, resistance, disease resistance or tolerance, standibility and maturity.

Review yield data from multiple replicated trials if possible: A variety that has the highest yield potential under ideal conditions may not yield as well as others when confronted with yield-limiting factors. The best way to account for this variability is to look at yield data from as many different environments as possible. Research has shown that evaluating variety performance over a wide range of locations and over multiple years will help you select the best varieties for your farm. Since varieties have a relatively short life span, multiple-location data is easier to obtain than multiple-year data.

Later-maturing varieties usually can be expected to have higher yields than earlier-maturing types. If you wish to correctly compare yields, do so only between varieties with similar calendar dates of maturity, usually within 3 to 5 days. More reliable comparisons can be made using variety yields from several consecutive years.

Soybean Cyst Nematodes: Soybean cyst nematodes are the most damaging soybean pest. Once a field is infested, planting resistant varieties will protect yield and significantly reduce soybean cyst nematodes populations. Ask your seed supplier to tell you the source of the resistance. Rotating resistance sources will help prevent the nematodes from overcoming resistant varieties.

For proper management of fields with soybean cyst nematodes, it is recommended that varieties with a "Resistance" rating be planted. If a soil test is taken in the field where soybeans are to be planted in 2010 and the soybean cyst nematode population numbers are relatively low (3,000), a variety with a "Moderate Resistance" rating might be considered. Varieties rated "Low Resistance and Susceptible" should not be considered where soybean cyst nematode is present.

Phytophthora root rot: Consider selecting varieties that have specific race resistance or a high level of tolerance to phytophthora when planting in fields with marginal drainage. Phytophthora root rot can cause significant yield reductions if susceptible varieties are planted in poorly drained, infested fields. There are several known races of this fungus, so it is important to know which are present in a particular field. Genes can be incorporated into varieties to provide resistance to specific races of this disease.

Seed suppliers are the best source of information on the level of tolerance that varieties exhibit to phytophthora. The most common resistance genes that are widely effective are Rps 1c and 1k. Rps1a can be effective, but is not as effective in many areas as the other genes. Rps 3 and other genes can also be effective. For areas where the Rps genes are not working well due to the presence of pathogen races that overcome the resistance, cultivars with high levels of field tolerance (or partial resistance) should be planted. Crop rotation and tillage may be of some benefit.

Iron chlorosis: Frequently, soybeans that are grown on fields which have a pH of 7.4 or greater turn yellow, and, in some cases, die. This condition is described as iron chlorosis. There is no deficiency or shortage of iron in the soil. Because of soil and/or environmental conditions, the soybean plant is not able to absorb or take up the amount of iron that is needed for normal growth and development. Careful variety selection is of major importance.

The University of Minnesota publication, "Varietal Trials for Farm Crops," has chlorosis scores for many varieties. The majority of the companies that market soybean seed also provide chlorosis scores for their varieties.

White Mold: White mold, also known as sclerotinia stem rot, develops in infested fields when high relative humidity and moderate temperatures occur during soybean flowering. Planting varieties less susceptible in wider row spacings or at lower populations is the most effective method of reducing the severity of white mold

Accurate ratings for soybean variety resistance to white mold are difficult to obtain because both infection and disease development depend on weather conditions. Because of this variability, a variety's performance can change significantly among locations and years depending on the interaction of plant development, precipitation, relative humidity, and temperature.

White mold severity also tends to be greater if lodging occurs. Growers concerned about variety performance in the presence of white mold should select varieties that show consistently less white mold during several years of testing.

David Nicolai is a crops educator with the University of Minnesota Extension Service Regional Center, Hutchinson.

HUTCHINSON -- Variety selection is one of the most important management decision producers make. Utilize the University of Minnesota Varietal Trials Soybean Performance Report -- at http://www.maes.umn.edu/10varietaltrials/ -- and information from seed companies and your on-farm trials to select high-yielding, well-adapted varieties.

Consider the following characteristics: yield, resistance, disease resistance or tolerance, standibility and maturity.

Review yield data from multiple replicated trials if possible: A variety that has the highest yield potential under ideal conditions may not yield as well as others when confronted with yield-limiting factors. The best way to account for this variability is to look at yield data from as many different environments as possible. Research has shown that evaluating variety performance over a wide range of locations and over multiple years will help you select the best varieties for your farm. Since varieties have a relatively short life span, multiple-location data is easier to obtain than multiple-year data.

Later-maturing varieties usually can be expected to have higher yields than earlier-maturing types. If you wish to correctly compare yields, do so only between varieties with similar calendar dates of maturity, usually within 3 to 5 days. More reliable comparisons can be made using variety yields from several consecutive years.

Soybean Cyst Nematodes: Soybean cyst nematodes are the most damaging soybean pest. Once a field is infested, planting resistant varieties will protect yield and significantly reduce soybean cyst nematodes populations. Ask your seed supplier to tell you the source of the resistance. Rotating resistance sources will help prevent the nematodes from overcoming resistant varieties.

For proper management of fields with soybean cyst nematodes, it is recommended that varieties with a "Resistance" rating be planted. If a soil test is taken in the field where soybeans are to be planted in 2010 and the soybean cyst nematode population numbers are relatively low (3,000), a variety with a "Moderate Resistance" rating might be considered. Varieties rated "Low Resistance and Susceptible" should not be considered where soybean cyst nematode is present.

Phytophthora root rot: Consider selecting varieties that have specific race resistance or a high level of tolerance to phytophthora when planting in fields with marginal drainage. Phytophthora root rot can cause significant yield reductions if susceptible varieties are planted in poorly drained, infested fields. There are several known races of this fungus, so it is important to know which are present in a particular field. Genes can be incorporated into varieties to provide resistance to specific races of this disease.

Seed suppliers are the best source of information on the level of tolerance that varieties exhibit to phytophthora. The most common resistance genes that are widely effective are Rps 1c and 1k. Rps1a can be effective, but is not as effective in many areas as the other genes. Rps 3 and other genes can also be effective. For areas where the Rps genes are not working well due to the presence of pathogen races that overcome the resistance, cultivars with high levels of field tolerance (or partial resistance) should be planted. Crop rotation and tillage may be of some benefit.

Iron chlorosis: Frequently, soybeans that are grown on fields which have a pH of 7.4 or greater turn yellow, and, in some cases, die. This condition is described as iron chlorosis. There is no deficiency or shortage of iron in the soil. Because of soil and/or environmental conditions, the soybean plant is not able to absorb or take up the amount of iron that is needed for normal growth and development. Careful variety selection is of major importance.

The University of Minnesota publication, "Varietal Trials for Farm Crops," has chlorosis scores for many varieties. The majority of the companies that market soybean seed also provide chlorosis scores for their varieties.

White Mold: White mold, also known as sclerotinia stem rot, develops in infested fields when high relative humidity and moderate temperatures occur during soybean flowering. Planting varieties less susceptible in wider row spacings or at lower populations is the most effective method of reducing the severity of white mold

Accurate ratings for soybean variety resistance to white mold are difficult to obtain because both infection and disease development depend on weather conditions. Because of this variability, a variety's performance can change significantly among locations and years depending on the interaction of plant development, precipitation, relative humidity, and temperature.

White mold severity also tends to be greater if lodging occurs. Growers concerned about variety performance in the presence of white mold should select varieties that show consistently less white mold during several years of testing.

David Nicolai is a crops educator with the University of Minnesota Extension Service Regional Center, Hutchinson.

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