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Biolog Microbial Identification System, Version 4.2 (Biolo~. Inc.,
Hayward, CA), the isolates were identified as Pseudomonas viridiflava
with a Biolog similarity index range of 0.52 to 0.72 afte~ 24 h. ~e~u.lts of
LOPAT tests (2) of isolates were identical to that of atypical ~ vmdifIava
reponed by Gonzalez
er
aI. (I). Levan production and pectolytic
acuvny
of
the isolates were variable. All isolates were POSI~V~ fo~ tobacco
hypersensitivity and negative for oxidase reaction and ~gmme dihydrolase
production. The 165 rDNA region (1,442 bp) of the Isolates (GenBank
Accession Nos. HMI90218-HMI90224; P. viridijlava CFBP2107
T
=
HMI90229), amplified by using universal PCR primers, shared 100%
sequence identity with atypical
P.
viridijlava (GenBank
Accession
No.
AM182934) (I). The gyrB sequence (638 bp) from the isolates (GenBank
Accession Nos. HMI90232-HMI90238;
P.
viridijlava CFBP2107
T
=
HMI90239), amplified by using previously reported ~R primers (3), had
a distance index value range of 0.029 to 0.031 With that of the
P.
viridif/ava CFBP2107T (=BC2597) as determined by Juk~s-Cantor ~odel
using MEGA Version 4.1 (4). On the basis of phenotypic characteristics
and the sequences. the seven isolates were identified as atypical
P.
viridif/ava. The disease is named "bacterial leaf spot". To our knowledge,
this is the first report of bacterial leaf spot of rape caused by atypical
P.
viridiflava.
Reftrtnces: (I) A. J. GoozaJez
ec
aI. Appl. Environ. Microbiol. 69:2936. 2003. (2) R.
A. Lelhou et aI. J. Appl. Bactt:rioI. 29:470. 1966. (3) H. Sawada et aI. J. Mol. Evol.
49:627.1999. (4) K. Tamura
ec
aI. Mol. BioI. Evol. 24:1596, 2007.
• The
e-Xtra logo stands ror "electronic extra" and indicates this Disease NOIe online
contains supplemental material tIOIincluded in the print edition.
First Report of Brown Ring Patch Caused by Wailea circinata var.
circinat« on Poa annua In Wisconsin and Minnesota. J. P. Kerns and
P. L. Koch. Department of Plant Pathology. University of Wisconsin-
Madison; B. P. Horgan, Department of Horticultural Science. University of
Minnesota. SI. Paul; and C. M. Chen and
F.
P. Wong, Department of Plant
Pathology, University of California, Riverside. Plant Dis. 94: 1165, 2010;
published online as doi:1O.l094lPDlS-94-9-1165A. Accepted for publi-
cation 22 June 2010.
In summer of 2008. two turfgrass samples were submitted to the
Turfgrass Diagnostic Lab at the University of Wisconsin-Madison. The
samples were from golf courses in Beaver Dam, WI on 12 June and
Minneapolis. MN on 14 July. Both samples were collected from 4O-year-
old native soil putting greens mowed at 3.2 mm that had received annual
sand topdressing since 1992. The putting greens were a mixture of
approximately 75% annual bluegrass (Poa annua L.) and 25% creeping
bentgrass (Agros/is stolonifera L.) Stand symptoms observed in the field
were bright yellow, sunken rings that were approximately 5 ern thick and
15 to 35 cm in diameter. Some rings were incomplete, giving a scalloped
appearance. Affected plants were severely chlorotic and lacked any dis-
crete lesions or spots, Symptoms were more prominent on annual blue-
grass than creeping bentgrass. Upon incubation of samples at room tem-
perature in a moist chamber for 24 h, fungal mycelia with septations and
right-angle branching were observed in the foliage and thatch layer. Two
isolates were obtained from affected annual bluegrass in each sample.
Isolations were performed by washing affected leaves in 0.5% NaOCI
solution for 2 min. blotting the tissue dry, and plating the tissue on potato
dextrose agar (PDA) amended with chloramphenicol (0.05 g/liter), strepto-
mycin (0.05 g/liter), and tetracycline (0.05 glliter). After incubation for 2
days at 23°C, isolates were transferred and maintained on PDA. All four
isolates had multinucleate hyphae and displayed sclerotial characteristics
similar to those reported for Wailea circinata VIr. circinata (2). Sequenc-
ing the ITS IFIITS4-amplified rDNA internal transcribed spacer (ITS)
region confirmed the isolates as W. circinata var. circinata, with ~%
sequence similarity to published W. circinata var. circinate ITS sequences
(GenBank Accession No. FJ755849) (1.2.4). To confirm pathogenicity.
isolates were inoculated onto 6-week-old annual bluegrass (True
PuttlDWl84) grown in 10-cm-diameter pots containing calcined clay
(Turface; Profile Products LLC .. Buffalo Grove, IL). Two 4-mm-diameter
agar plugs for each isolate were removed fro~ the margins of 3-day-old
colonies grown on PDA and placed near the soil surface to ensure contact
with the lower leaf blades. Each isolate was placed in four separate pots to
have four replicated tests per isolate, and four ~ested pots were util-
ized as negative controls. All ~ .were placed m ~tChambers at 28°C
with a 12-h light/dark cycle. Wtthin 4 to 6 days,
lDOCulated
plants exhib-
ited severe chlorosis and a minor amount of aerial' mycelium was
observed. Inoculated plants became necrotic after 15 to 20 days, while the
noninoculated plants remained healthy. W.
circinata
var.
circinata
was
reisolated from inoculated plants and its identity was confirmed by mor-
phological and molecular characteristics. This pathogen was previously
reported as a causal agent of brown ring patch of creeping bentgrass in
Japan and annual bluegrass in the western United States (2.4). To our
knowledge, this is the first report of brown ring patch in Minnesota and
Wisconsin. Intensive fungicide practices are needed to control brown ring
patch; therefore, this disease could have significant economic impact
throughout the Upper Midwest (3).
References: (I) C. M. Chen et al. Plant Dis. 93:906. 2009 (2) K. de la Cerda et al.
Plant Ois. 91:791, 2001. (3) J. Kaminski and F. Wong. Golf Course Manage.
75(9):98.2007. (4) T. Toda et aI. Plan! Ois. 89:536. 2005.
DifTerential Response by Melaleuca quinquenervia Trees to Attack
by the Rust Fungus Puccinia psidii In Florida. M. B. Rayamajhi,
P. D. Pratt, T. D. Center. and G. S. Wheeler, USDA-ARS. lnvasive Plant
Research Laboratory, Fort Lauderdale, FL. Plant Dis. 94:1165,.2010;
published online as doi: 1O.l094IPDIS-94-9-1165B. Accepted for publica-
tion 3 June 2010.
Me/aleuca quinquenervia (melaleuca) is an exotic invasive tree in Flor-
ida, Hawaii, and some Caribbean islands (1,2).
Puccinia
psidii (rust fun-
gus) attacks melaleuca as well as other plants in a few genera of the
Myrtaceae and Heteropyxidaceae, both members of the Myrtales (1,2) .
Disease occurs on succulent stems and foliage of melaleuca, causing twig
dieback and defoliation (3). Melaleuca trees growing under similar field
conditions exhibit susceptible or resistant reactions toward this fungus. To
document this differential susceptibility of melaleuca to P.psidii, we visu-
ally evaluated 331 field-grown melaleuca trees from southeast Florida for
occurrence of disease attributes: pustules (susceptible), nonpersistent halos
(resistant), or asymptomatic (no macroscopic symptoms) conditions on
leaves and succulent twigs during February and March when symptoms
were at their peak. Percentages of trees manifesting susceptible. resistant.
and asymptomatic responses to this fungus were 85.8, 13.0, and 1.2%,
respectively. A screenhouse study was conducted to corroborate these
observations by raising plants from composite seed sources and maintain-
ing them in seven 3.8-liter plastic pots that were filled with commercial
potting media. Nine to eleven plants per pot (with new foliage) were indi-
vidually tagged, grown to 30 to 45 cm high, and spray inoculated (during
February and March) with uredospores (-2
x
1()6/ml) obtained from
melaleuca trees and suspended in water. Inoculated plants were placed on
a screenhouse bench under infected trees and subjected to additional
inoculum. thereby simulating field conditions. Evaluations made weekly
during a 4-week period revealed that susceptible, resistant. and asympto-
matic seedlings constituted 63.3, 33.6, and 3.2%, respectively, of the
tagged plants. To assess the stability of these fungal and host attributes
over time and space, we multiplied two
P.
psidii susceptible and two resis-
tant plants from cuttings. We spray inoculated 6 to 13 rooted cuttings from
each plant types with uredospores (0.8 to 2
x
1()6/ml) obtained from dis-
eased melaleuca trees and suspended in water. These plants were incu-
bated in a dew chamber for 72 to 96 h under 100% relative humidity at 19
to 23°C maintained with a l2-h fluorescent light cycle. After incubation.
plants were placed randomly on a bench in a screenhouse (21 to 23°C) and
evaluated weekly for symptom development during a 4-week experimental
period. Noninoculated controls were maintained as well. The experiment
was repeated twice. Foliage of the resistant plants developed a few incipi-
ent halos whereas
1000/0
of the susceptible plants developed erupted ured-
inia and were defoliated in both replications. No detectable change in
P.
psidii virulence and melaleuca susceptibility patterns was observed.
Despite wide host range within Myrtales, resistance to
P.
psidii exists
within M. quinquenervia. Other
P.
psidii susceptible host systems of eco-
nomic and environmental importance may have host/pathogen relation-
ships similar to that of melaleuca and the selection of resistant individuals
from their affected populations may be possible. Additional studies will be
needed to ascertain the attributes of virulence or resistance in this rust
fungus-melaleuca association.
References: (I) M. Glen et al. Australas, Plant Pathol. 36:1, 2007. (2) P. D. Pratt et al.
J. Aquat. Plant Manag. 45:8. 2007. (3) M. B. Rayachhetry et aI. Biol. Control 22:38.
2001.
(Disease Notes continued on next page)
Plant Disease
I
September 2010 1165
