American Journal of Plant Sciences, 2010, 1, 104-105
doi:10.4236/ajps.2010.12013 Published Online December 2010 (http://www.SciRP.org/journal/ajps)
Damping-Off of Festuca arizonica Caused by
Fusarium
Mopuri N. Reddy1*, Stanley H. Faeth2
1Department of Applied Microbiology, S P Mahila Visvavidyalayam, Tirupati, India; 2Department of Biology, University of North
Carolina at Greensboro, Greensboro, USA.
Received August 12th, 2010; revised September 3rd, 2010; accepted October 28th, 2010.
ABSTRACT
We report here a damping-off disease occurring at the seedling stage, resulting in severe loss of the seedling stands
caused by an important soil-borne fungal pathogen, Fusarium oxysporum. Endophyte-infected plants appear to be more
resistant to the damping-off disease than uninfected plants.
Keywords: Damping-off, Endophytes, Festuca arizonica, Fusarium
1. Introduction
Damping-off is a very common soil-borne disease caused
by fungi, usually by the species of Rhizoctonia, Pythium,
Fusarium, Sclerotinia, Sclerotium. Damping-off disease
affects seeds, germinating seeds and seedlings of many
plant species, including grasses. It is a major cause of
poor stand establishments in agricultural and nursery
plantings.
Arizona fescue (Festuca arizonica Vasey) (Pooideae)
is a perennial bunch grass native to Arizona, Nevada,
New Mexico and Colorado in the USA and in northern
Mexico and is an important forage grass for livestock and
native vertebrates [1]. Arizona fescue grows in semi-arid
grasslands and forests at the elevations between 2300m
and 3200m. Arizona fescue, like many pooid grasses, is
often infected (60-100% infections among populations)
with the systemic, asexual and seed-borne fungal endo-
phyte in the genus Neotyphodium [2]. The effects of this
endophytic fungus on plant performance, competition
and resistance to herbivores and pathogens has been well
studied [3-5]. In general, Neotyphodium endophytes are
thought to act mutualistically with their hosts by increas-
ing resistance to drought, invertebrate and vertebrate
herbivor es and plant pathogen s [3], although more recen t
studies show highly variable effects of infection, espe-
cially in non-agronomic, native grasses [4,5].
Although Arizona fescue is an important and dominant
forage grass in the southwestern USA, little attention has
been focused on the diseases occurring in this native
grass and whether endophyte infection provides any re-
sistance to these diseases. We report here a damping-off
disease occurring at the seedling stage of Arizona fescue
that results in loss of the seedling stands and compare
infection in endophyte-infected and endophyte-free
grasses.
2. The Disease
In the experimental green house plots containing four
plant genotypes of Festuca arizonica with (E+) and
without (E-) Neotyphodium endophytes grown from seed
in native soils, severe damping-off, with rapid yellowing
and death of young seedlings, was observed. Th e disease
appeared within a week after emergence of seedlings and
the intensity was very severe. The disease was consis-
tently observed to be more severe in the genotypes with-
out (E-) endophyte as compared to those with endophyte
(E+) (Figure 1).
The disease is characterized by light brown to slightly
darkened water-soaked lesions, on hypocotyls of young
seedlings, which rapidly enlarge, resulting in the rapid
death of the seedlings (Figure 1). The young seedlings
are mainly attacked at or below the soil line and the dis-
ease incidence and intensity or severity varied with the
genotype.
The infected hypocotyl tissues appear soft and light to
dark brown in color (Figure 2). The basal portions of
invaded seedlings appear thinner than the areas above the
lesions resulting in fall over an d death of the seedling . To
diagnose the disease and its causal organism, infected
seedlings were carefully lifted and then excavated and

Damping-Off of Festuca Arizonica Caused by Fusarium
105
Figure 1. Damping-off of Arizona fescue showing yellowing,
collapsed, and wilted seedlings in pot 2 as compared to
healthy seedlings in pot 1. A+ refers to a grass genotype
associated with endophy te and A- to grass genotype without
endophyte.
Figure 2. Symptoms on hypocotyls – brown water-soaked
lesions and collapse of the seedlings.
rinsed with sterile water so that seedlings remain ed intact
after extraction.
3. Isolation and Identification of the
Pathogen
The original isolations were made on PDA medium, by
surface sterilization and plating the infected tissues or the
lesions. Single spore isolations were obtained and tested
for pathogenicity on healthy seedlings by following
Koch’s Postulates. To fulfill Koch’s Postulates, samples
of experimentally infected seedlings were removed and
assayed to verify the presence of the causal agent. The
re-isolated fungus was cultured on PDA and cultural
characteristics were recorded and compared to the origi-
nal isolate. Typical disease symptoms on hypocotyls
were initiated by third day after inoculation of the seed-
lings. Eventually seedlings collapsed and died. Many
seeds failed to germinate when the seeds were sown in
the Fusarium infested soil and complete rotting of the
seeds was evident when they were extracted and ob-
served.
Based on the morphological and cultural characteris-
tics, the pathogen was identified as Fusarium oxysporum
and confirmed by the Fusarium Research Center, Penn-
sylvania State University, University Park PA, USA.
A search of the world literature in Biological Reviews
and the Phytopathology Reviews including USDA Hand
Books for occurrence of the disease on F. arizonica re-
veals that there is no report of occurrence of damping-off
caused by Fusarium oxysporum. Hence, this may be the
first report of this fungal disease on F. arizonica.
This pathogen may be a potential candidate for studies
in testing the pathogen resistance of Arizona fescue and
other cool-season pooid grasses associated with Neoty-
phodium endophytes. Endophytes are generally under-
studied relative to their in teractions with plant pathogens
and mycorrhizae yet hold great potential promise for
pasture and turf grass improvement [3]. Our preliminary
results suggest differential susceptibility to the pathogen
based upon Neotyphodium infecti on of the h ost grass.
4. Acknowledgements
The authors are indebted to Jean Juba, Fusarium Re-
search Center, Pennsylvania State University, U S A, for
confirming the identification of the Fusarium isolate as
Fusarium oxysporum and to Sally Wittinger for technical
assistance. Support was provided by the School of Life
Sciences, Arizona State University, Tempe, USA to Prof
M. N. Reddy, as Visiting Professor and by NSF Grants
DEB 0613551 and 091774 1 to S.H.F.
REFERENCES
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