Nov. i, 1915 
Potato Tuber-Rots Caused by Fusarium Spp. 
*93 
inoculation with strain 1733, a reisolation of strain 1635, which in turn 
was a reisolation of an original strain 1485 obtained from the discolored 
vascular system of the main root of a wilting cotton plant from Florence, 
S. C., on June 15, 1912. Culture used, 26-day-old pionnotes on stem of 
Melilotus alba. 
F. vasinfectum 3167; reisolation of 1855, on June 19, 1914, from Idaho 
Rural potato in above experiment, after 25 days' incubation at 25.5 0 C. 
Culture used, 19-day-old pionnotes on a potato cylinder. 
The results with tubers inoculated with F. vasinfectum 1855 after an 
incubation period of 25 days at an average temperature of 25.5 0 were as 
follows: The five tubers of the Netted Gem variety remained sound; one 
of the three tubers of the Idaho Rural variety and all of the People's 
variety were rotted, the organism being recovered from both varieties. 
With strain 3167, one of these reisolations, only 75 per cent of the tubers 
of the Pearl variety were rotted after 51 days' incubation at an average 
temperature of 21.5 0 C. These tubers were attacked only where a com¬ 
paratively large cut surface had been exposed to the inoculum. The 
organism was recovered in each attempt, three reisolations being made. 
F. vasinfectum 3263; isolated in September, 1914, as a particularly 
virulent strain of the cotton-wilt fungus from supposedly wilt-resistant 
cotton obtained in breeding experiments from Denmark, S. C. Culture 
used, 20-day-old potato cylinder. 
F. vasinfectum 3243; isolated on September 5, 1914, from the vascular 
bundles of a wilting okra plant from Wrightsboro, N. C. Culture used, 
20-day-old potato cylinder. 
With F . vasinfectum , strains 3263 and 3243, the results were less con¬ 
clusive. In tubers inoculated with the former strain the organism per¬ 
sisted for 41 days at average temperatures of 18.3° and 18.9° without 
perceptible damage. Of 10 tubers at 23.5 0 for 41 days, 5 were rotted, 
the organism being recovered from 3 of them and F . radicicola being 
isolated from 2. The organism persisted in the other 5 tubers, though 
no rot resulted. With strain 3243 the organism persisted for 51 days at 
17.8° and 18.4° without damage to the tubers. One tuber at 24.6° for 
24 days was badly rotted, and the organism was recovered; of 9 tubers 
at 23.5 0 for 41 days, only one rotted. The organism was not recovered, 
but F. radicicola was isolated. 
In this connection it may be noted that in one experiment (p. 202), 
which included F. vasinfectum 1855 and two strains of Veriicillium albo - 
atrum among other organisms, some of the tubers inoculated with the 
species of Verticillium and likewise certain controls rotted; from these 
the organism used could not be recovered, but F. vasinfectum was isolated 
several times. 
Table III gives the data of the inoculations with F. vasinfectum . 
