Progress 07/01/00 to 06/30/06
Outputs
A field experiment was conducted to determine the affects of soybean planting date on the soil population density of Macrophomina phaseolina. The planting dates were mid-April, mid-May, and mid-June during 2000-2003. Planting date did not affect the soil population density of M. phaseolina, but the differences in soil population density among years were significant. These results suggest that soybean producers should not be concerned about planting date directly affecting M. phaseolina soil population densities. Phomopsis seed decay (PSD) caused by Phomopsis spp. can be severe when soybean growers in the southern USA use the Early Soybean Production System (ESPS). The objective of this research project was to determine the affects of fungicides (benomyl and azoxystrobin) applied to soybean on percent Phomopsis spp. infection of seed. The percent Phomopsis spp. infection of Asgrow 3834 seed averaged over years was significantly less for benomyl (0.28 kg a.i. ha-1)
applied at R3 + R5 treatment (48.6% seed infection) than the control (52.8% seed infection). Azoxystrobin did not reduce the percent of seed infected with Phomopsis spp. The objective of a second project was to determine the effects of planting dates on seed infection by Phomopsis sp. and on yield and the correlation between percent of seed infected with Phomopsis sp. and seed quality. Generally, yields averaged over years were significantly greater for mid-April than mid-June plantings, and yields of cultivars were similar within a planting date. Soybean lines SS 93-6012 and SS 93-6181 were highly resistant to Phomopsis seed decay compared to the susceptible cultivar, Asgrow 3834. There was a significant, negative correlation between germination of seeds from mid-April plantings of Asgrow 3834 and percentage of these seeds infected with Phomopsis species. Moreover, there were significant correlations between fatty acid composition of Asgrow 3834 seeds and the percent of these seeds
infected with Phomopsis species. This altered composition of fatty acids may be responsible for reduced quality of oil derived from seeds infected with this fungus. Phomopsis seed decay resistant soybean lines SS 93-6012 and SS 93-6181 should be useful in breeding programs focused on developing high yielding cultivars. The objective of a third research project was to determine H. glycines race shift in field populations due to continuous planting soybean cultivars. Race shifts were not predictable based on the source of resistance of the soybean cultivar planted. The objective of a fourth project was to determine US soybean yield suppression due to diseases during 1996 to 1998. Total yield losses caused by soybean cyst nematode in the United States were greater than those caused by any other disease. Next in importance were Phytophthora root and stem rot, brown stem rot, Sclerotinia stem rot, and seedling diseases. Yield loss due to particular diseases varied by region of the United
States and among years. The estimates of soybean yield losses to diseases in the United States were 10.9 million metric tons in 1996, 11.9 million t in 1997, and 14.0 million t in 1998.
Impacts
Soybean planting date did not affect the soil population density of M. phaseolina, but the differences in soil population density among years were significant. These results suggest that soybean producers should not be concerned about planting date directly affecting M. phaseolina soil population densities.
Publications
- Wrather, J. A., Shannon, J. G., and Mengistu, A. 2007. Impact of soybean planting date on soil population density of Macrophomina phaseolina. Online. Plant Health Progress doi:10.1094/PHP-2007-In Press.
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Progress 01/01/05 to 12/31/05
Outputs
One of the objectives of this project is to screen soybean lines and varieties for resistance to soybean cyst nematode (SCN) and then incorporate resistant lines into the MU Soybean Breeding Program to develop high yielding SCN resistant cultivars. We have identified variability within SCN populations in Missouri, identified sources of resistance to various populations of SCN present in Missouri, and developed soybean cultivars resistant to various races or biotypes of SCN. During 2005, we released three new soybean lines with resistance to SCN; S99-3181, S99-11509, and S99-11986. Each of these has good resistance to SCN and high yield potential, and each would be useful in a soybean breeding program.
Impacts
Soybean producers in the US and certainly in Missouri need soybean cultivars resistant to native SCN populations to avoid yield suppression. This nematode suppressed soybean production in the US 76.2 million bushels valued at $457.3 million. Unfortunately, there is great diversity for parasitism within SCN communities in most areas of the US, and this nematode quickly adapts to new resistant soybean cultivars. Efforts must continue to screen lines for resistance to established populations of SCN and then incorporate useful resistance into cultivars. Currently, the only effective methods for managing this pest are crop rotation and planting resistant cultivars.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Phomopsis seed decay (PSD) caused by Phomopsis spp. can be severe when soybean growers in the southern USA use the Early Soybean Production System (ESPS). Usefulness of this production system would be greater if seeds could be protected from PSD by foliar application of fungicides or by planting Phomopsis spp. resistant soybean lines. The objective of this research was to determine the affects of fungicides (benomyl and azoxystrobin) applied to soybean on percent Phomopsis spp. infection of seed from mid-April planted Asgrow 3834, a PSD susceptible cultivar, and SS93-6012, a PSD resistant soybean line. The percent Phomopsis spp. infection of Asgrow 3834 seed averaged over years was significantly less for benomyl (0.28 kg a.i. ha-1) applied at R3 + R5 treatment (48.6% seed infection) than the control (52.8% seed infection). Azoxystrobin did not reduce the percent of seed infected with Phomopsis spp. The percent of Phomopsis spp. infection of Asgrow 3834 seed for all
fungicide treatments was significantly greater than for line SS93-6012 treated with benomyl at R3 + R5 or not treated. There were no differences in percent Phomopsis spp. infection of SS93-6012 seed among the control and fungicide treatments. The most effective method for PSD management was to plant a resistant soybean line.
Impacts
Phomopsis seed decay of soybean has reduced quality and value of seed from early maturing, MG III and IV, soybean cultivars planted in early- to mid-April in the southern United States. Soybean cultivars resistant to Phomopsis seed decay have not been available until the recent release of germplasm line SS 93-6012. Application of fungicides to a Phomopsis seed decay susceptible soybean variety did not reduce the incidence of this disease. The only effective tool available for management of this disease is planting varieties with resistance to this disease from soybean line SS 93-6012.
Publications
- Wrather, J. A., Shannon, J. G., Stevens, W. E., Sleper, D. A., and Arelli, A. P. 2004. Soybean cultivar and foliar fungicide effects on Phomopsis sp. seed infection. Plant Disease 88:721-7232.
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Progress 01/01/03 to 12/31/03
Outputs
Incidence of Phomopsis seed decay is frequently high and quality low in seed from early maturing, MG III and IV, soybean cultivars planted in early- to mid-April in the southern United States. Cultivars resistant to this disease have not been available until the recent release of germplasm lines SS 93-6012 and SS 93-6181. Our objective was to determine the effects of planting dates with these lines and one Phomopsis seed decay susceptible soybean cultivar, Asgrow 3834, on seed infection by Phomopsis sp. and on yield and the correlation between percent of Asgrow 3834 infected with Phomopsis sp. and seed quality. Generally, yields averaged over years were significantly greater for mid-April than mid-June plantings, and yields of cultivars were similar within a planting date. Soybean lines SS 93-6012 and SS 93-6181 were highly resistant to Phomopsis seed decay compared to the susceptible cultivar, Asgrow 3834. There was a significant, negative correlation between
germination of seeds from mid-April plantings of Asgrow 3834 and percentage of these seeds infected with Phomopsis species. Moreover, there were significant correlations between fatty acid composition of Asgrow 3834 seeds and the percent of these seeds infected with Phomopsis species. This altered composition of fatty acids may be responsible for reduced quality of oil derived from seeds infected with this fungus. Phomopsis seed decay resistant soybean lines SS 93-6012 and SS 93-6181 should be useful in breeding programs focused on developing high yielding cultivars.
Impacts
Cultivars resistant to Phomopsis seed decay have not been available until the recent release of germplasm lines SS 93-6012 and SS 93-6181. This disease has reduced quality and value of seed from early maturing, MG III and IV, soybean cultivars planted in early- to mid-April in the southern United States. Phomopsis seed decay resistant soybean lines SS 93-6012 and SS 93-6181 should be useful in breeding programs focused on developing high yielding cultivars.
Publications
- Wrather, J. A., D. A. Sleper, W. E. Stevens, J. G. Shannon, and R. F. Wilson. 2003. Planting date and cultivar effects on soybean yield, seed quality, and Phomopsis sp. seed infection. Plant Disease 87: 529-532.
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Progress 01/01/02 to 12/31/02
Outputs
Soybean cultivars with different sources of resistance to Heterodera glycines were grown at three locations initially infested with races 2, 3, and 6 in order to investigate H. glicines race shift in field populations. Race shifts were not predictable based on the source of resistance of the soybean cultivar planted. Furthermore, race designations were influenced by the time of sampling and temperature at which the race tests were conducted.
Impacts
The variability of H. glycines populations in both field and greenhouse situations diminishes the value of race test results when making cultivar recommendations.
Publications
- Colgrove, A. L., Smith, G. S., Wrather, J. A., Heinz, R. D., and Niblack, T. L. 2002. Lack of predictable race shift in Heterodera glycines-infested field plots. Plant Dis. 86:1101-1108.
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Progress 01/01/01 to 12/31/01
Outputs
Soybean disease loss estimates were compiled for the 1996 to 1998 harvested crops from all soybean-producing states in the United States. Scientists from each state provided estimates of losses based on field surveys, information from field workers and university extension staff, and research plot data. Total yield losses caused by soybean cyst nematode in the United States were greater than those caused by any other disease. Next in importance were Phytophthora root and stem rot, brown stem rot, Sclerotinia stem rot, and seedling diseases. Yield loss due to particular diseases varied by region of the United States and among years. The estimates of soybean yield losses to diseases in the United States were 10.9 million metric tons in 1996, 11.9 million t in 1997, and 14.0 million t in 1998.
Impacts
Diseases caused extensive reductions in soybean yield in the United States from 1996 to 1998. The value of these losses at $220/metric ton was $2.4 billion in 1996, $2.6 billion in 1997, and $3.1 billion in 1998. These data may be useful to scientists and research funding agencies when developing priorities for research.
Publications
- Wrather, J. A., Stienstra, W. C., and Koenning, S. R. 2001. Soybean disease loss estimates for the United States from 1996 to 1998. Canadian Journal of Plant Pathology 23:122-131.
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Progress 01/02/00 to 12/31/00
Outputs
Soybean disease loss estimates were compiled for the 1996 to 1998 harvested crops from all soybean-producing states in the United States. Scientists from each state provided estimates of losses based on field surveys, information from field workers and university extension staff, and research plot data. Total yield losses caused by soybean cyst nematode in the United States were greater than those caused by any other disease. Next in importance were Phytophthora root and stem rot, brown stem rot, Sclerotinia stem rot, and seedling diseases. Yield loss due to particular diseases varied by region of the United States and among years. The estimates of soybean yield losses to diseases in the United States were 10.9 million metric tons in 1996, 11.9 million t in 1997, and 14.0 million t in 1998.
Impacts
Diseases caused extensive reductions in soybean yield in the United States from 1996 to 1998. The value of these losses at $220/metric ton was $2.4 billion in 1996, $2.6 billion in 1997, and $3.1 billion in 1998. These data may be useful to scientists and research funding agencies when developing priorities for research.
Publications
- No publications reported this period
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Progress 01/01/99 to 12/31/99
Outputs
Soybean disease loss estimates were compiled for the 1998 harvested crop from the top 10 soybean producing countries in the world. These 10 countries (United States, Brazil, China, Argentina, India, Canada, Paraguay, Indonesia, Italy, and Bolivia) produced 97.6 percent of the world's total soybean crop in 1998. Total yield losses caused by soybean cyst nematode {8,969,400 metric tons (t)} in these 10 countries were greater than those caused by any other disease. Next in order of total yield reduction caused were brown spot (2,588,200 t), charcoal root rot (2,015,300 t), and Sclerotinia stem rot (1,474,200 t). The total yield loss due to diseases in these countries during 1998 was 28.5 million metric tons, valued at $6.29 billion. Yield losses due to a particular disease varied by country. For example, yield losses due to rust (258,900 t)were reported only from China and Indonesia. Soybean disease control research and extension efforts are needed to provide more
effective preventive and therapeutic disease management strategies and systems to producers.
Impacts
Diseases caused extensive reductions in soybean yield in the top 10 soybean producing countries during 1998. The total estimated soybean yield losses due to diseases in these countries was 28,522,300 metric tons, valued at $6.29 billion. Yield losses in some countries may have been worse if not for the use of disease management strategies and systems.
Publications
- Wrather, A., Anderson, T. R., Arsyad, D. M., Gai, J., Ploper, L. D., Porta-Puglia, A., Ram, H. H., and Yorinori, J. T. 1999. Soybean disease loss estimates for the top ten soybean producing countries in 1998. Pages 632-633 in: Proceedings World Soybean Research Conference VI. Chicago, IL.
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Progress 01/01/98 to 12/31/98
Outputs
Reduced-tillage production systems have become popular with soybean farmers in the United States. During 1992 to 1994, soil and soybean root samples were collected from disk-tillage, no-tillage, and moldboard plow treatments in an experiment conducted since 1979 at the University of Tennessee in Jackson. The objective was to determine if reduced-tillage production systems affected charcoal rot incidence and severity. There were no differences at planting in soil population density of _Macrophomina phaseolina_ in the 0- to 15-cm layer of soil among treatments. However, the soil population density of _M. phaseolina_ in disk-tillage and no-tillage plots was significantly greater in the 0- to 7.5-cm layer of soil than in the 7.5- to 15-cm layer. Similarly, soil population densities were significantly greater in the 0- to 7.5-cm layer of soil in no-tillage than in either disk-tillage or moldboard plowed plots. Tillage did not affect the number of _M. phaseolina_ infection
sites in 6-week-old plant roots or the percentage of root segments of physiologically mature plants colonized by _M. phaseolina_. There was no significant correlation between soybean yield and _M. phaseolina_ soil population density. These data suggest that long-term tillage did not affect charcoal rot incidence and severity.
Impacts
(N/A)
Publications
- Wrather, J., Kendig, S. R., and Tyler, D. D. 1998. Tillage effects on _Macrophomina phaseolina_ population density and soybean yield. Plant Disease 82:247-250.
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Progress 01/01/97 to 12/31/97
Outputs
Soybean disease loss estimates were compiled for the 1994 harvested crop from 10 countries with the greatest soybean production. The objective was to document the major soybean disease problems in these countries and any recent changes in the severity of individual soybean diseases. Total yield losses caused by Heterodera glycines in these 10 countries were greater than those caused by any other disease. Next in order of importance were stem canker, brown spot, and charcoal rot. The total yield loss due to disease during 1994 in these countries was 14.99 million metric tons, valued at $3.31 billion. Methods used to estimate soybean disease losses were field surveys, plant disease diagnostic clinic samples, variety trial data, information from field workers and university extension staff, research plots, grower demonstrations, and private crop consultant reports. Yield loss estimates due to a particular disease varied by country. For example, yield losses due to rust
were reported from China and Indonesia, but no losses due to this disease were reported from any of the remaining eight countries.
Impacts
(N/A)
Publications
- WRATHER, J. A., et al. 1997. Soybean disease loss estimates for the top 10 soybean producing countries in 1994. Plant Disease 81:107-110.
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Progress 01/01/96 to 12/30/96
Outputs
Experiments were conducted in a field near Portageville, MO, to determine cultivar and planting date effects on soybean stand, yield, and seed infection with fungi. Soybean cultivars Asgrow 3733 (maturity group III), Ring Around 452 (maturity group IV), Hutcheson (maturity group V), and Asgrow 6785 (maturity group VI) were each planted in 75-cm wide rows in tilled soil. The planting dates were mid-April, mid-May, and mid-June. Yields of Hutcheson and Asgrow 6785 were similar for all planting dates and were greater than yields of Asgrow 3733 for all planting dates. The percentage of seed infected with Phomopsis sp. was greater in Asgrow 3733 than for the other cultivars in mid-April and mid-May plantings. The percentage of seed infected with Phomopsis sp. was low in Asgrow 6785 each year and was similar for all planting dates. Low yields and problems of seed infection with Phomopsis must be resolved for early planting of Asgrow 3733 to be a practical production system
in the upper mid-south. Mid-April planting of Hutcheson and Asgrow 6785 may be a practical cropping system for the upper mid-south because yields, stands, and seed infection with Phomopsis sp. were similar to those of mid-May plantings and harvest was earlier.
Impacts
(N/A)
Publications
- Wrather, J. A., Kendig, S. R., Wiebold, W. J., and Riggs, R. D. 1996. Cultivar and planting date effects on soybean stand, yield, and Phomopsis sp. seed infection. Plant Dis. 80:622-624.
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Progress 01/01/95 to 12/30/95
Outputs
A three year experiment, 1992 - 1994, was conducted in the upper Mississippi delta region near Portageville, Missouri to determine cultivar and planting date effects on soybean stand, yield and seed infection with fungi. Soybean cultivars in maturity groups III, IV, V, and VI were planted mid-April, mid-May or mid-June each year. Stands were similar among all cultivars and planting dates each year. Yields of MG V and VI cultivars were similar for all planting dates and were greater than yields of MG III cultivars. The percentage of seed infected with Phomopsis sp. was greater in MG III cultivars than over the other cultivars in mid-April and mid-May plantings. The percentage of seed infected with Phomopsis sp. was low in MG VI cultivars each year and was similar for all planting dates. Low yields and problems of seed infection with Phomopsis must be resolved for early planting of MG III cultivars to be a practical production system in the upper Mississippi delta
region. Mid-April planting of MG V and VI cultivars may be a practical cropping system for this area because yields, stands, and seed infection with Phomopsis sp. was similar to mid-May plantings and harvest was earlier.
Impacts
(N/A)
Publications
- WRATHER, J. A., KENDIG, S. R. WIEBOLD, B. J. and RIGGS, R. D. 1995. Cultivar and planting date effects on soybean stand, yield and Phomopsis sp. seed infection. Plant Disease 80: In press.
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Progress 01/01/94 to 12/30/94
Outputs
A four year experiment, 1991-1994, was conducted in a field where sudden death syndrome (SDS), had developed previously. The objective was to determine the effect of tillage, planting date, and soybean cultivars on the percentage of leaves with SDS at R6 growth stage. The soybean cultivars Essex, Forrest, Hartwig, and Rhodes were each planted in 75-cm wide rows in disc-tilled, ridge-till, and no-till plots. The planting dates were mid-May, mid-June, and late-June to early-July each year. Symptoms of SDS developed in 1991, 1992, 1994 and did not occur in 1993. There were significant year x cultivar (P=0.0001), and tillage x planting date x cultivar (P=0.05) interactions for the percentage of leaves with symptoms of SDS. The percentage of leaves with symptoms of SDS was higher in Essex, Forrest, and Rhodes than Hartwig in 1991 and 1994; differences among cultivars did not occur in 1992. The percentage of Essex, Forrest, and Rhodes leaves with symptoms of SDS was higher
for no-till than either disc-till or ridge-till in mid-May plantings. There were no significant correlations between the percentage of leaves with SDS and yield.
Impacts
(N/A)
Publications
- WRATHER, A., KENDIG, S., NIBLACK, T., and SMITH, G. 1994. Effects of tillage, planting date, and cultivar on the severity of sudden death syndrome. (Abstr.) Proceedings World Soybean Research Conference V, page 35.
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Progress 01/01/93 to 12/30/93
Outputs
Experiments were conducted over two years to determine the effect of tillage systems, row widths, and soybean cultivars on foliar diseases in double-crop soybean. The soybean cultivars Pershing, susceptible to bacterial blight, and Avery, resistant to bacterial blight, were each planted in 38-cm and 75-cm row widths in soil under conventional tillage or no-tillage following winter wheat. There was a significant interaction (P=0.0001) between tillage and cultivar for the severity of bacterial blight and a significant interaction (P=0.001) for tillage, cultivar, and year for the severity of brown spot. Tillage did not influence bacterial blight severity on Avery; however, disease severity was higher on Pershing soybean in tilled plots. Generally, brown spot severity was higher in 1986 than in 1985, lower on Avery than Pershing in both years, and higher in tilled than no-tilled conditions. Row width did not affect the severity of these diseases.
Impacts
(N/A)
Publications
- WRATHER, J. A., ANDERSON, S. H., WOLLENHAUPT, N. C., ANAND, S. C., and KENDIG, S. R. 1993. Effects of tillage, row width, and cultivar on foliar diseases of double-crop soybean. Plant Dis. 77:1151-1152.
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Progress 01/01/92 to 12/30/92
Outputs
Soil samples were collected from a long-term (14 year) tillage experimental at Jackson, TN and were analyzed for the population density of Macrophomina phaseolina. Soil samples from the 0-7 and 7-14 cm depths were collected from within the row and between rows at the time soybean was planted in June. The population density of M. phaseolina was significantly greater in the 0-7 cm depth, and less in the 7-14 cm depth in no-till than tilled plots. There were no differences in population density in soil from between and within rows. We developed a technique to test soybean seedlings for resistance to root infection by Fusarium solani Type A (causal agent of sudden death syndrome). Forty cultivars and 60 lines have been tested. Symptoms of root infection were significantly less on six of the cultivars and six of the lines than on the susceptible cultivar Spencer. The symptoms on PI86425 were less severe than on any other line or cultivar.
Impacts
(N/A)
Publications
- WRATHER, J. A., NIBLACK, T. L., and MILAM, M. R. 1992. Survey of plant parasitic nematodes in Missouri cotton fields. Supp. J. Nematol. 24:779-782.
- WRATHER, J. A., NIBLACK, T. L., SMITH, G. S., and ANAND, S. C. 1992. Effect of tillage, planting date, and cultivar on the severity of sudden death syndrome, septoria brown spot and downy mildew of soybean. (Abstr).
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