Phialophora gregata
| Phialophora gregata | |
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| Species: | P. gregata
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| Binomial name | |
| Phialophora gregata (Allington & D.W. Chamb.) W. Gams, (1971)
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Cadophora gregata | |
Phialophora gregata is an ascomycete fungus that is a plant pathogen that causes the disease commonly known as "brown stem rot of soybean." The fungus exists infects as two strains. [1] P. gregata does not produce survival structures.
Symptoms and Signs
Phialophora gregata’s infection of a soybean plant is accompanied by browning of the plant’s vascular and pith tissues.[1] The plant often exhibits chlorosis and necrosis, as well as leaf browning.[1] Wilting and defoliation are also known to occur. [1] Signs of infection often go unnoticed until reproductive stages of a plant’s life cycle. They can be diagnosed earlier on by opening the stem and visualizing the pathogen. One can visualize signs by cutting open the stem in early stages of infection, [1] but symptoms do not become apparent until after the soybean pod formation. [2]
Depending on which strain infects the plant, genotype A or genotype B, the effect is more or less potent. Genotype A causes browning of stems as well as foliar symptoms such as interveinal chlorosis, defoliation and wilting. [1] [3] Symptomatic leaves have a shriveled appearance, but remain attached to the stem. [3] These foliar symptoms can often be confused by those caused by the pathogen "Fusarium virguliforme," which causes Sudden Death Syndrome in soybean. [3] [2] Genotype B causes only browning of stems. [3] Secondary symptoms of brown stem rot are stunting, premature death, decrease in seed number, reduced pod set, and decrease in seed size. [3]
Secondary symptoms of brown stem rot are stunting, premature death, decrease in seed number, reduced pod set, and decrease in seed size. [3]
Environment
As the disease is soilborne, it is not uncommon to find clusters of diseased plants together. [3] The pathogen proliferates in stem tissues when soil has high moisture content and air temperatures from 70-80 degrees Fahrenheit [3]. Rainy seasons promote brown stem rot. [3] When soil is untilled, the disease is more likely to persist in soil. [3] The incidence of brown stem rot is highest at soil pH ~6.3. [4]
External links
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References
- ^ a b c d e f Grau, C. "Brown Stemrot of Soybeans." <http://fyi.uwex.edu/fieldcroppathology/files/2010/11/bsr_063.pdf>
- ^ a b Monsanto. "Brown Stem Rot and Sudden Death Syndrome in Soybean." Lewis Hybrids. Lewis Hybrids, 2010. Web. <http://www.lewishybrids.com/files/File/Agronomic%20Spotlight%20-%20Brown_Stem_Rot_Sudden_Death_Soy.pdf?PHPSESSID=0c6bc72c5c097a7e80e53605fd2effce>
- ^ a b c d e f g h i j Robertson, A. & Tabor, G. “Soybean Brown Stem Rot.” Iowa State University. <http://www.extension.iastate.edu/Publications/PMR1004.pdf.>2012.
- ^ Pedersen, Palle. “Brown Stem Rot.” <http://extension.agron.iastate.edu/soybean/diseases_bsr.html> 2006.