Pythium volutum
Cause of Pythium Root Dysfunction
By Troy Taylor
A Class Project for PP728: Soilborne
Plant Pathology
North Carolina State University
Department of Plant Pathology
Fall, 2008
Introduction: Pythium volutum is the causal agent of Pythium root dysfunction on turf in the southeastern United States (2). In the upper midwest this disease was shown by Hodges (4) in 1985 to be caused by Pythium arrhenomanes, P. aristosporum and P. vanterpoolii. Pythium volutum was first associated with Pythium root dysfunction in 2002 in North Carolina. At first the disease was diagnosed by many in the southeast as take-all patch caused by Gaeumannomyces graminis. But isolation of this pathogen from infected turf proved unsuccessful. Further evaluation of the infected root systems revealed an abundant mass of Pythium oospores and hyphae. This fungus was later identified as Pythium volutum (2).
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Host range and
distribution: Pythium volutum infects creeping
bentgrass putting
greens in the southeastern United States. It
is most damaging to greens constructed within the last
10 years. Creeping bentgrass existing at
optimum
growing conditions is much more resistant to the disease than poorly
managed
turf. Pythium volutum has
been isolated from creeping bentgrass in
Virginia, North Carolina, South Carolina and Georgia. It has also been isolated from oats in
Canada, the Netherlands, and England. It
has been reported on both marsh horsetail and western dock in Poland and Pyhtium
volutum has also been isolated
from common wheat in the United States (5).
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Figure 1: Pythium volutum symptoms and root cross section
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Isolation: Isolation of Pyhtium
volutum can be done directly from infected roots by plating
on V8 agar. A more popular method and
perhaps more successful is isolation by baiting onto creeping bentgrass
leaf
blades (2). Leaf blades are then transfer to V8 agar to obtain culture. |
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Figure 2: Close up of roots infected with Pythium volutum
Identification: Isolates should be
transferred to
grass leaf blade cultures to induce sporangia, oospore and antheridia
production (2). Isolates of P.
volutum produce both lobulate
sporangia and relatively large oospores measuring 27 to 33 um long and
2.8 um
wide. Isolates are also characterized by
production of three to nine diclinous antheridia.
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Figure 3: Microscopic features of P. volutum Figure 4: Microscopic view of roots infected with P. volutum
Symptoms: Pythium root dysfunction
appears in
circular or irregular patches up to two feet in diameter, which
initially
display signs of wilt or nutrient deficiency.
Infected turf then turns orange or yellow as dieback from the
leaf tip
begins and eventually the turf collapses.
Root tips of infected turf are bulbous.
The roots are completely void of root hairs and have a loose
cortical
structure. Reductions in both root mass
and depth of root system can be seen in both the fall and the spring
but roots
begin to die back rapidly when soil temperatures reach higher than 85
degrees
Fahrenheit.
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Figure 5: Pythium volutum symptoms Figure 6: Pythium volutum symptoms
Ecology and life cycle: Pythium volutum is believed to infect
creeping
bentgrass turf species in the fall and spring when soil temperatures
are
between 50 and 75 oF. The
disease is favored by both low fertility and drought stress, however
wet soils
are important for P. volutum to cause
an initial infection. While initial
infection in the southeastern United States occurs in the spring or
fall
symptoms of the disease aren’t readily seen until the summer.
References:
1.
Tredway, Lane P., and James P. Kerns Aug. 2005.
Defining the Nature of Creeping Bentgrass Root Disease. 13
Nov. 2008
http://www.usga.org/turf/green_section_record/2005/jul_aug/defining.html
2.
Kerns, James P., and Lane P. Tredway 28 Jan. 2008 First Report of
Pythium
Root Dysfunction of Creeping Bentgrass Caused
Pythium
Volutum in North Carolina. 13 Nov. 2008 http://www.apsnet.org/pd/searchnotes/2007/PDIS-91-5-
0632C.asp
http://www.turffiles.ncsu.edu/Diseases/Pythium_Root_Dysfunction.aspx
4.
Hodges, Clinton F. 1985. Pythium-
Induced Root Dysfunction of Creeping
Bentgrass
on High Sand Content
Greens. 13 Nov. 2008
http://turf.lib.msu.edu/1980s/1985/850911.pdf
5.
Farr, D.F., & Rossman, A.Y. Fungal Databases, Systematic Mycology
and
Microbiology
Laboratory, ARS, USDA.
Retrieved December 1, 2008, from
http://nt.ars-grin.gov/fungaldatabases/
6.
Hodges CF. 1985. Pythium-Induced Root Dysfunction of Secondary Roots of
Agrostis
palustris. Plant Disease 69:336-40.
Links to
other sites: