Aug. 15, 1924 
Bacterium Marginatum on Gladioli 
167 
in a moist case, the infection showed 
plainly in from 3 to 5 days. If moist 
conditions were continued, a rather 
extensive soft rot occurred, the tissues 
becoming gray-green and water-soaked. 
Sterilized soil, sterile water, and a 
pure culture of the bacteria were mixed, 
then spattered over the leaves of healthy 
plants. No effort was made to wound 
the epidermis. This inoculum was 
kept moist for 12 hours by placing the 
plants in a moist case. The plants 
were then returned to the open bench 
where the usual watering quickly 
washed off the soil particles. Tiny 
spots due to the bacteria were noted on 
the sixth day and by the ninth day the 
largest spots were 2 mm. in diameter. 
There were 200 or more spots on the 
inoculated side of the leaves. The 
opposite side where no inoculated soil 
had been placed had a few scattered 
infections. The spots enlarged, co¬ 
alesced, and caused the death of the 
inoculated leaves. 
Soil from outdoor beds where dis¬ 
eased gladioli had grown the previous 
season has been used to inoculate 
gladioli. The soil was moistened with 
sterile water and spread in a thick 
layer over the lower leaf parts of vigor¬ 
ous greenhouse plants or by placing on 
the leaves a layer of cotton soaked 
with the soil and water mixture. The 
moist condition of the soil inoculum was 
retained for several days by keeping 
the plants in a moist chamber. This 
experiment was tried in May, 1922, in 
April, 1923, and in March, 1924. No 
infections resulted from any of these 
inoculations. 
Garden soil from plats where the 
gladiolus disease had occurred for three 
seasons was brought into the green¬ 
house in January and healthy gladio¬ 
lus corms were planted in it. These 
corms had the husks removed and the 
surface sterilized by a 15-minute treat¬ 
ment in a mercuric chloride, 1-1000, 
solution. Examination in June showed 
definite and typical spots on the new 
corms and isolation plates from both 
husk and corm spots gave pure cultures 
of Bacterium marginatum. Control 
plants in sterile soil showed no signs of 
infection. 
On corms the lesions produced by 
inoculation w T ere slower in growth than 
those on leaves. Development may 
be more rapid under more favorable 
conditions. The quickest results were 
secured on young, growing corms by 
removing enough soil to expose most 
of the corm but without disturbing 
any of the roots. The soil particles 
were washed off, bits of the husk were 
loosened and lifted so that bacteria 
could be placed directly on the uninj ured 
surface of the corm. The husks were 
replaced and the corm again covered 
with the soil. Typical brown pits, 1 
to 4 mm. in diameter, were found 
4 weeks after such inoculations and 
pure cultures of Bacterium marginatum 
secured from them. 
In other corm inoculations the 
bacteria were placed on the husks or 
the soil was thoroughly wet several 
times during the growing season with 
water containing bacteria. Both of 
these methods gave infections but they 
were slower in developing than the 
preceding. 
That mature corms are less subject 
to infection than young, growing corms 
was shown in the following experiment. 
Seventy healthy, husked, and sterilized 
corms were planted in pots in sterilized 
soil. Most of these were inoculated 
with pure cultures of Bacterium mar¬ 
ginatum, others with crushed lesions 
from diseased corms. These dry lesions 
taken from corms harvested several 
months previously were pounded in a 
mortar and softened with water. In 
each case the inoculum was poured over 
the uninjured corms when planted. 
The inoculation was repeated several 
times during the early growing period 
by pushing the soil away and pouring 
the inoculum over the corms. When 
harvested only 13 of the 70 old corms 
showed signs of infection. In 31 pots 
of this lot of 70 the inoculation was 
resumed during the growth of the new 
corms and 27 of the new corms (of the 
lot of 31) had typical husk and corm 
lesions from which the bacteria were 
isolated and their pathogenicity proved. 
Fifty-two healthy, husked, and steri¬ 
lized corms were planted in pots in 
sterile soil. Pure cultures of Bacterium 
gummisudans ( 3) , also fresh leaf lesions 
caused by that organism, were used to 
inoculate these corms. The inoculum 
was applied and repeated at intervals 
as in the preceding experiment. When 
mature a few typical husk spots and 
corm pits were found on three of the 
new corms. Isolation plates were 
made from all three and in each case 
Bacterium marginatum was secured 
but not a single colony of Bacterium gum¬ 
misudans. These 52 plants were grown 
in the same greenhouse and at the 
same time as those inoculated with 
Bacterium marginatum. They were on 
separate benches and care was exer¬ 
cised to avoid contaminations. It is 
not known just how these three corms 
became infected with Bacterium mar¬ 
ginatum. 
Twelve healthy corms, husked, steri¬ 
lized, and planted in sterile soil were 
99181—25f-2 
