166 
Journal o f Agricultural Research 
Vol. XXIX, No. 4 
same plants. Because of this fact, 
particular care was taken to discover 
which, if either, was responsible for the 
corm spots. 
Having also in mind the' hard-rot 
disease of gladioli (4) caused by 
Septoria gladioli Passer and which 
produces on the corms lesions that 
sometimes resemble those caused by 
Bacterium marginatum , a careful watch 
was kept on the fungi isolated from 
diseased corms. No Septoria has been 
found among the various fungous 
growths secured. No Septoria disease 
has occurred on the gladioli, seedlings, 
or mature plants, used for experimental 
purposes in Washington and none has 
been observed in the various other 
plantings of gladioli from which dis¬ 
eased corms have been obtained. 
Virulent colonies of Bacterium mar¬ 
ginatum have been isolated in July from 
corms harvested the preceding October, 
thus definitely proving that the bacteria 
can survive on the stored corms from 
season to season. 
For isolation from the gummy 
exudate from corm lesions, pieces of 
clean-looking gum were selected, rinsed 
quickly in sterile water, then dissolved 
in beef boullion. The plates from this 
unsterilized gum produced various 
growths, a fair proportion of which were 
Bacterium marginatum. 
Infected leaves from which typical 
bacteria were isolated in August were 
kept in the laboratory all winter. The 
following March several efforts to 
isolate bacteria from lesions on these 
leaves resulted in failure. 
Late in the fall some dry leaves were 
collected from the field. All parts 
were dark in color but the bacterial 
lesions could easily be distinguished. 
Examination showed that the bacteria 
were in small, isolated pockets in the 
lesions and under pressure oozed out in 
a thick mass. Typical Bacterium mar¬ 
ginatum colonies were secured from 
this material. 
Efforts were made to isolate the 
organism from plant parts that had 
remained in the field all winter. All 
the soft tissues had disintegrated, 
leaving only the flower stalks and the 
fibrovascular bundles of the leaves. 
Platings were made from black spots 
found on the stalks and from fibrous 
remains of leaves but among the great 
numbers of colonies that appeared in 
the plates there was none that resem¬ 
bled Bacterium marginatum. 
No success has resulted from several 
attempts to isolate the organism from 
soil in which diseased plants had grown 
but the organism has been kept alive 
and virulent in both dry and moist soil 
in culture tubes for 11 months. 
The pathogenicity of the bacteria 
isolated was proved in each case by 
successful inoculation and reisolation. 
Bacteria from leaf spots produced 
typical pits on corms and bacteria 
reisolated from these corms produced 
typical leaf infections. No difference 
in pathogenicity has been noted in the 
bacteria obtained from leaves, husks, 
or corms, from the different varieties of 
gladioli, or from different localities. 4 
INOCULATIONS 
Numerous inoculation experiments 
have been made on sound gladioli, 
both in the greenhouse and outdoors. 
Bacteria from leaf lesions produced 
infection on both leaves and corms, 
and bacteria from corms as readily 
infected leaves as corms. Numerous 
isolations from leaves and corms have 
been tested and all seem essentially 
alike. In some of the early inocula¬ 
tions needle pricks were made, but it 
was soon found that it is not necessary 
to wound the epidermis. Bacteria from 
young agar cultures were diluted in 
sterile water and applied to the leaves 
either by spraying with an atomizer 
or spread on with a bit of cotton. Be¬ 
cause of the extremely smooth surface 
and perpendicular position of gladiolus 
leaves it was often difficult to keep the 
inoculum on the leaf. Sometimes a 
few wet fibers of cotton were put on 
the inoculated areas. In others the 
smoothness of the leaf was somewhat 
reduced by rubbing with a bit of 
cotton. In dry weather, out of doors, 
a layer of wet cotton was placed over 
the inoculated area. 
Under average summer conditions 
in the field the infections show defi¬ 
nitely on the leaves in from 7 to 12 
days after inoculation as tiny, isolated 
spots of bright reddish-brown color, 
usually very numerous in the area inoc¬ 
ulated. These by enlargement and 
coalescence form the larger lesions (PI. 1). 
In the greenhouse, if the inoculated 
plants were kept for the first 24 hours 
4 Dr. Ivan C. Jagger isolated Bacterium marginatum from gladioli grown in Florida from corms 
obtained from a New York firm. The disease appeared during the summer rainy season. Doctor 
Jagger states: 
During four years spent largely in Florida I examined several small plantings of gladioli, and 
invariably found no leaf spots. Generally gladioli are planted out in the late fall or early winter so that 
they come into bloom rather early in the spring, when the weather is quite generally dry and un¬ 
favorable for leaf blights. My planting, which developed bacterial leaf spot, was made much later 
in the season than is favorable for best results. 
