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A total of 191 somaclones were generated from leaf explants ID 83843 and 3 Kimberly, ID 83341; 2 of 'Bulgaria 12', a tomato cultivar with partial resistance
to Clavibacter michiganensis subsp. michiganensis (CMM),
causal organism of bacterial canker of tomato. Thirty-two
percent of the somaclones were discarded due to abnormal
phenotype or poor growth. One aberrant Rl line produced
currant-type fruit on a vine. Fifty-five R1 progeny were
screened for resistance to CMM in a growth chamber. There
were some variations in reaction to CMM among progeny regenerated
from the same individual callus. A few R1 lines showed
an increased level of resistance to CMM and could prove useful
to plant breeders.
261
Epidemiology and spread of Clavibacter michiganensis subsp.
michiganensis on tomato. R. J. Chang, S. M. Ries and J. K.
Pataky. Dept. of Plant Path., Univ. of Illinois, Urbana.
Harris-Moran Seed Co., San
Juan Bautista, CA 95045.
Black chaff of gramineacious crops, caused by Xanthomonas cam-
pestris pv. translucens (Xct) develops from seedborne inoculum.
A program was established in Idaho to produce Xct-free seed.
In 1987 and 1988, black chaff occurred in spring wheat fields
grown from Xct-free seed at Tetonia and Aberdeen. Epiphytic
populations of Xct were found on leaves of known hosts (Bromus
inermis, Agropyron repens) and on previously undescribed hoata
(Poa pratensis, Festuca arundinaceae, F. rubra, Hordeum lepori-
num, Medicago sativa) near these fields. Black chaff symptoms
were not observed, but they contained populations of 13 cfu to
7.5 x 106 cfu per gram fresh tissue. Pathogenicity tests
indicated a broad and variable host range, with high levels of
virulence on wheat and barley. Xct was not isolated from plants
in southwest ID where black chaff does not occur frequently.
Ten rifampin-resistant mutants of Clavibacter michiganensis
subsp. michiganensis (CMM) were used to study the epidemiology
and spread of bacterial canker. CMM spread from infected to
healthy plants in beds of 10,000 direct seeded plants clipped
six times with a rotary mower. Initial disease incidences of
0.01, 0.05, 0.1 and 0.5% resulted in 4, 8, 12 and 83% infected
plants, respectively, when clipped plants were transplanted.
CMM also was spread during transplanting when healthy and
diseased plants were pulled, shaken, and mixed together in
shipping crates. Twelve, forty-two and fifty-two per cent of
the transplanted plants showed canker symptoms when initial
proportions of diseased plants placed in crates were 1, 5, and
10%, respectively. A susceptible and a tolerant cultivar
supported epiphytic populations of CMM of 107-109 CFU/g fresh
weight, although symptoms of secondary infection, marginal
scorch of leaflets, were more severe on the susceptible
cultivar.
265
PSEUDOMONAS VIRIDIFLAVA, THE CAUSE OF A STEM CANKER OF POINSET-
TIA PLANTS. Arthur W. Engelhard and Jeffrey B. Jones. Univ.
of Florida, IFAS, Gulf Coast Research & Education Center,
Bradenton, FL 34203
A stem canker occurred in December 1984 on potted poinsettia
plants grown outdoors near Bradenton, Florida. A fluorescent
bacterium was isolated that caused a positive reaction for
tobacco hypersensitivity, DL-lactate, D(-) tartrate, erythritol
and a negative one for arginine dihydrolase, oxidase and levan.
It, thus, was identified as Pseudomonas viridiflava. Two
strains of the bacterium tested'were patho"geni-con all seven
cultivars of poinsettia plants evaluated, although the culti-
vars varied in susceptibility. The disease was most severe at
10 and 15*C, mild at 27.70C. and no disease occurred at 32.2°C
These Florida strains of P. viridiflava are not expected to
262
become a serious problem in poinsettia plant production in
Florida because of their low optimum temperature requirement
for their pathogenicity.
Survival of wildtype and gentically-altered Erwinia carotovora
subsp. carotovora (ECC) strains in soil. H.K. Austin, G.H. Lacy
qnd J. Cairns, Jr., UCE&HMS and the Laboratory for Molecular 266
Biology of Plant Stress, VPI&SU, Blacksburg, VA 24061-0331.
CYPROCONAZOLE: A NEW SYSTEMIC FUNGICIDE FOR TURF DISEASE
We assessed survival of genetically-altered, kanamycin-resistant MANAGEMENT. G. G. Thomas, W. B. O'Neal, and P. Schmid.
L-864 and wildtype, rifampin-resistant L-863 strains of ECC in Sandoz Crop Protection Corporation, 1300 East Touhy Avenue,
non-amended soil; in soil amended with germinating seeds of rad- Des Plaines, IL 60018.
ish, carrot, tomato (all hosts), or grass (non-host); and in
soil amended with potato tuber pieces or enrichment medium (EM; Cyproconazole, a-(4-chlorophenyl)-(l cyclopropylethyl l)-l 1,2,
Phytopathology 66:367-370, 1976). Survival of a genetically- 4-triazole-l-ethanol, is a new broad spectrum fungicide with
altered, pectate lyase-deficient ECC strain L-872 in soil excellent systemic activity. Cyproconazole has rapid plant
amended with potato tuber pieces or EM was also studied. L-863 tissue penetration and is translocated primarily acropetally.
and L-864 did not differ significantly (P > 0.05) in response to At low dosages(O.1 to 0.4 kg a.i./ha) cyproconazole has
seedlings, potato pieces, or EM; their densities increased > demonstrated control of a wide range of fungi important in
500-fold with potato pieces (P < 0.01). Indigenous bacteria turf grass disease management. Common diseases, brown patch
increased 30-fold in soil amended with potato pieces or the caused by Rhizoctonia solani and dollar spot caused by
polygalacturonic acid EM. Survival and detection of the geneti- Sclerotinia homoeocarpa have been effectively controlled for
cally-altered ECC was enhanced in soil amended with potato tuber a period of three to five weeks following application. In
pieces or EM. addition to foliar disease control, cyproconazole has shown
potential to control turf grass root diseases; necrotic ring
spot caused by Leptosphaeria korrae and summer patch caused by
263 Magnaporthe poae.
COLLOIDAL GOLD/PROTEIN A IMMUNOBLOT ASSAY FOR Clavibacter xyli
subsp, xyli CAUSE OF RATOON STUNTING DISEASE OF SUGARCANE. 267
K. E. Damann. Jr. and W. J. Todd. Dept. of Plant Path. & Crop
Physiol., and Dept. of Vet. Science, LABS, LSU Agricultural CONTROL OF IRIS RUST WITH FUNGICIDES. Albert 0. Paulus and
Center, Baton Rouge, LA 70803. Robert 0. Raabe. Departments of Plant Pathology, University of
A one-step assay for
California,
detection of
Riverside
Clavibacter
92521
xyli
and
subsp,
Berkeley
xyli
94720.
was developed. Application of 1 ul of vascular extract or Rust of iris, resulting from infection by
sugarcane
Puccinia
sap
irndia,
from ratoon
is
stunt-diseased or healthy cultivar comimon in coastal California.
L 62-96
Bearded
to
iris
a nitrocellulose
(Iris germanica),
strip gave a positive red-purple Dutch iris (I. xiphium and I. filifolia x I. xiphium) and a
color in response to infected plants. This occurred when
strips were incubated
Pacific
for
coast
1 hr
native,
with 1 ml
I.
of
munzii,
protein A/gold
are particularly
and In
susceptible.
experiments to control rust
10
on Dutch
ul of a
iris
100-fold
cv. Blue
dilution
Ribbon
of
in
antiserum to either C. x. southern California, plants were sprayed
subap,
3
xyli
times
or
at
C.
2-week
x. subsp, cynodontis. The technique was intervals. Diniconazole gave excellent
also used
control,
in tissue
Mobay
blots
1608
by centrifuging vascular contents gave very good control and flusilazole
from 1
and
cm stalk
myclobutanil
sections
gave
onto a nitrocellulose filter. The moderately good control. In northern
distribution
California,
of colored
sprays
spots
were
on the filter was compared with applied 3 times at 3-week intervals
the
to seedlings
distribution
of bearded
of vasucular bundles exhibiting alkaline- iris. Best control resulted with Ciba Geigy 453
induced
and myclobutanil.
metaxylem autofluorescence in the stalk section. Mdrtl odcnrlrsle ihoyabxn eoai
Theresltswil bedisussd.and Nor Am SN 596. Control with Nor Am SN 39865, penconazole,
triadimefon, prochloraz, and benomyl was not satisfactory.
264 268
NEW PERENNIAL HOSTS OF EPIPHYTIC POPULATIONS OF XANTHOMONAS
CAMPESTRIS PV. TRANSLUCENS. 0. C. ThompsonI, N. W.~Schaad, FLOWERING OF FLORIBuNDA ROSES IN RESPONSE TO WEEKLY APPLICATIONS
and R.C. Forster 3 . IDept. PSES, University of Idaho, Moscow, OF A COMBINATION AND SINGLY APPLIED FUNGICIDE SPRAY. P. F.
1168 PHYTOPATHOLOGY