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of Plant Pathology and Weed Science, Mississippi State Univ.,
Miss. State, MS 39762.
42
Cloned fragments of T-DNA from a wide host range Ti plasmid,
pTi-A6, and from a limited host range plasmid, pTi-Ag63, have
been used as probes in DNA hybridization experiments to determine
the pathogenicity of isolates of Agrobacterium species from
stems, roots and galls of muscadine. Several hybridization
techniques including colony hybridization, slot blot, and Southern
hybridization have been used. These techniques consistently
identify known grape isolates, however, they are less sensitive
when used to probe unknown samples from muscadine isolates.
This suggests that the muscadine isolates may differ from Ag63
in DNA sequence homology. Attempts are being made to use the
polymerase chain reaction as a more sensitive detection technique.
39
EVALUATION OF SEED BIOPSY METHODS FOR NONDESTRUCTIVE SEED HEALTH
TESTING. P. M. Higley, D. C. McGee, J. S. Burris, Seed Science
Center and Dept. Plant Pathology, Iowa State Univ., Ames, IA
A previous report described methoda for extraction and detection
of pathogens from seeds for the purpose of developing nonde-
structive seed health tests. Of particular value was the hiopsy
method of coring tissue from dry seeds. The present work
focuses on optimizing coring techniques to minimize damage to
seed germination. Partial imbibition of corn, soybean, and
Phaseolus seeds facilitated removal of cores, but the combined
effect of imbibing and coring reduced germination compared to
that of seeds that were imbibed only. Treatment of wounded
tissue with a paraffin sealant was an ineffective means of
correcting deleterious effects of coring on germination.
However, reduction of the rate of dry-down by adjusting temperature
and humidity improved germination in cored and imbibed
soybean and Phaseolus seeds. Because corn germination was
unaffected by coring treatments in this experiment, effects of
COMPARISON OF THE ISOLATION OF XANTHOMONAS CAMPESTRIS PV.
CAMPESTRIS FROM CRUCIFER SEEDS IN FOUR SEMISELECTIVE MEDIA.
C. J. Chang', R. Donaldsoni, M. Crowley
these corrective actions were not detected.
2 , and D.
Pinnow
43
2 . lDepartment of Plant Pathology, University of
Georgia and 2 Seed Laboratory, Georgia Department of
Agriculture, Griffin, GA 30223.
INCIDENCE AND SURVIVAL OF SCLEROTINIA MINOR IN PEANUT
D. M. Porter, R. A. Taber, and D. H. Smith. USDA,
SEED.
ARS,
Four semiselective media, CS20ABN, NSCA, NSCAA, and F-S, were
compared for their efficacy in isolating Xanthomonas
campestris pv. campestris (Xcc) from crucifer seeds. Samples
of 50,000 seeds per lot were washed for 2 hr at room temp in
saline. The cheesecloth-filtered washings were centrifuged,
and the resuspended pellets were diluted and pipetted onto the
media. Saprophytic bacteria overgrew Xcc on NSCA and NSCAA
but not on F-S or CS20ABN. Colony-forming units (CFUs) of Xcc
ranged from 66-97 per plate at 10-1 or 37-259 at 10-2
on CS20ABN. Moreover, 59-100% of recovered colonies on
CS20ABN were Xcc, whereas only 4-29% were Xcc on F-S. Colony
size of Xcc on CS20ABN was 2-4 times that on NSCAA or NSCA,
but was 4-7 times that on F-S.
Tidewater Agric. Expt. Sta., Suffolk, VA 23437; Dept. Plant
Path. and Microbiology, Texas A&M Univ., College Sta., TX
77843.
The potential for seed transmission of Sclerotinia minor was
assessed in peanut seed harvested from fields with Sclerotinia
blight. The incidence of S. minor from 'VA B1B' peanut seed
harvested and dried in Virginia according to recommended
procedures was 4.2%. Seed with brown testa were colonized
more frequently (5.7%) than seed with tan or normal colored
testa (2.7%). The incidence of S. minor from seed with brown
testa from five field sites was 3.6, 4.6, 5.0, 7.6, and 7.8%.
The incidence from seed with tan testa from the same field
sites was 1.2, 2.8, 2.8, 3.0, and 3.6%. The incidence of S
minor from seed testa averaged 3.4% while the incidence from
cotyledonary tissues averaged 0.1%. A recommended seed
treatment (Botec 4 oz./cwt) reduced the incidence of S.
to 0.1%.
minor
40
MODIFIED TWEEN MEDIUM FOR DETECTING XANTHOMONAS CAMPESTRIS
PV. VESICATORIA IN TOMATO SEEDS. H. MKlim and N.W. Schaad.
Chonbuk Nat. Univ.,Chonju, Korea and Harris Moran Seed Co., San Juan
Bautista, Ca. 95045.
44
MOISTURE VARIABILITY AMONG INDIVIDUAL SEEDS OF SOYBEAN FROM THE
SAME POD BEFORE HARVESTING. F. A. Lazzari and R. A. Meronuck,
Department of Plant Pathology, University of Minnesota, St.
Paul, MN 55108.
X2712 omsc strspv vesc orl (X v ) i s s e d b orn e in t omat o.
Tween medium A has been described for Isolating Xv from fruit and
leaves (McGuireR.G. etal. Pl. Dis. 70: 887-891). The authors describe
the same medium plus boric acid and Increased cephalexin(Tween B)
for assaying seeds. Dilution platings on test media with xv and
tomato seed washings were done in comparison to KMB. Three of 8
strains failed to grow on Tween B. All strains grew on Tween B only
after reducing cephalexin, tobramycin and boric acid by 46,50 and 67
%, respectively.
incmaio
The
oKBrne
recovery in cfu
rm5-2
of 8 strains
ma
on modified
f7) euto
Tween
in seed flora on Tween B and modified Tween was similar (98 &97%).
Moisture is important in storability of soybeans. Variability
in moisture content (MC) among
may affect
single seeds
susceptibility
in stored
to
soybeans
invasion by storage fungi.
The moisture variability among single seeds of soybean from
different positions inside the same pod was
oven-dried
determined
single
using
The average MC of
seeds
individual
at 103
seeds
C for
from 72
the
hours
respective
in copper
position
cups.
were: 13.20% (seed near pedicel), 12.60% (middle seed), and
11.10% (farthest seed from pedicel).
The fresh weight of single seeds was inversely
to
proportional
seed),
the MC,
and
i.e.,
0.1451
0.1363
g (farthest
g (seed near
seed
pedicel),
from pedicel).
0.1430
While
g (middle
moisture content was highest in seeds nearest the
the
pedicel, the
fresh weight was lowest.
We conclude that variation in MC exists in mature seeds
inside the pod before harvest.
1140 PHYTOPATHOLOGY
45
SUPPRESSION OF STORAGE FUNGI IN GRAIN WITH SOYBEAN OIL.
0. C. McGee, A. lies and M. K. Misra, Seed Science Center,
Iowa State University, Ames, Iowa.
Effects of soybean oil, applied to grain at rates used to
reduce dust in elevators, on storage fungi, were examined.
Corn and soybeans at 17% and 15% moisture content,
respectively, were treated with soybean oil at 200 ppm, alone
or in combination with thiabendazole at 20 ppm, then stored
on-farm in aerated metal bins, with a capacity of 250 kg.
After 12 months, kernel infection by Penicillium and
Asoergillus app was 83.0% and 63.7%, respectively, in
untreated corn, compared to 60.0% and 46.2%, in soybean oiltreated
corn, and 24.7% and 17.0%, in soybean oil +
thiabendazole-treated corn. After 12 months, soybean seed
infection by Penicillium and Aspergillus spp. was 45.7% and
39.2% , respectively in untreated seeds, 17.7% and 8.2% in
soybean oil-treated seeds, and 1.7% and 2.0%, in soybean oil +
thiabendazole-treated seeds. The mechanism for reduction in
storage fungal growth by soybean oil was not fungicidal.