| Summary: | 碩士 === 國立中興大學 === 植物病理學系 === 85 === A total of 37 strains of soft-rot Erwinia were isolated
from the diseased plant tissues collected from colored calla
lily grown fields. Based on the physiological and
biochemical tests, they were all identified as Erwinia
carotovora subsp. carotovora. The incidence of rhizome rot of
colored calla lily caused by E. corotovora subsp. carotovora
was greater in the rhizomes artificially wounded than those
not artificially wounded. The soft rot incidenceof colored calla
lily cultivar Best Gold inoculated with E. carotovora subsp.
carotovora through the wounds just after flowers being plucked
was 100 %, while the incidence of rotting decreased to 16.7 %
when the inoculation was made 36 hours later. Rhizomes of
colored calla lily obtained from various sources were
detected for the soft-rot Erwinia, the results showed that 23.3
% ~ 84 % of rhizomes were contaminated with soft-rot Erwinia.
The number of soft-rot Erwinia on rhizomes of colored calla
lily after storage was detected on modofiedCVP selective medium.
The results showed that soft-rot Erwinia on rhizomes with cured
rotted lesions could reach to 104 ~ 106 cfu/g dry periderm. In
green housetest, the soft rot incidence of colored calla lily
grown from rhizomes with cured rotted lesions, rhizomes
which rotted lesions were excised and symptomlessrhizomes was
86.7 %, 33.3 % and 6.7 %, respectively. Sensitivity of the 37
strains of E. carotovora subsp. carotovora. to commercial
formulated agroche- micals was tested on nutrient agar plates.
It was found that all the Erwinia carotovora subsp.
carotovora strains tested were sensitive to basic copper
sulfate + cufram Z (500X), copper oxychloride + manzeb + zinzeb
(500X), cuprous oxide (500X), kasugamycin + copper oxychloride
(1000X), oxine-copper + copper hydroxide (500X) and tribasic
copper sulfate (500X). And with the exception of 1 ~ 3
strains, most strains tested were also sensitive to streptomycin
+ tetracycline (1000X), streptomycin sulfate (100 and 200
ppm) and thiophanate-methyl + streptomycin
(1000X), while all the strains tested were resistant to
mancozeb (400X), nonyphenol copper sulfonate (500X) and
tecloftalam (1000X). Treatment of rhizomes with agrochemicals
was able to reduce the population of E. carotovora subsp.
carotovora on the rhzomes artificially infested.
Chemical treatment of rhizomes at 45℃ were much better than
that at 26℃ to reduce the population of E. carotovora subsp.
carotovora onthe rhizomes. However, the effectiveness of
chemical treatment varied among the rhizomes treated. Copper
oxychloride + manzeb + zinzeb (500X) appeared to be the most
effective among 11 agrochemicals tested to reduce the population
of E. carotovora subsp. carotovora on the infested rhizomes.
When the infested concentration of E. carotovora subsp.
carotovora was at 108 cfu/ml, the number of E. carotovora
subsp. carotovora on the infested rhizomes after treated with
copper oxychloride + manzeb + zinzeb (500X) at 45℃ for 40
minutes could reduce to an undetected level. When the infested
concentration of E. carotovora subsp. carotovora was at 106 cfu/
ml, the number of E. carotovora subsp. carotovora on most of
the infested rhizomes after treated with both copper oxychloride
+ manzeb + zinzeb (500X) and thiophanate-methyl +
streptomycin (1000X) could also reduce to an undetected level.
In addition, soft rot incidence of both copper oxychloride +
manzeb + zinzeb (500X) and thiophanate-methyl + streptomycin
(1000X) treated rhizomes was much lower than that of untreated
rhizomes. Among 11 commercial growing media examined, no
soft-rot Erwinia was detected after enrichment in these
media. Survival of E. carotovora subsp. carotovora in these
growing media was studied, it was found that E. carotovora
subsp. carotovora could survive much better in these
media at low temperature (12℃) than at high temperature
(30℃). E. carotovora subsp. carotovora was able to survive
for over 180 days in vermiculite, perlite, Hydrocorn, TKS-1
Instant, volcano rock and sphagnum moss at 12℃, whereas they
could only survive less than 50 days at 30℃. High humidity
(RH 100 %) was favorable for E. carotovora subsp. carotovora to
survive on the leaves of colored calla lily. In addition,
application of 1 % of calcium nitrate solution to colored calla
lily during the growing season could increase the calcium
content of various parts of plants.
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