Nov. 1, 191S Potato Tuber-Rots Caused by Fusarium Spp. 193 



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, 191 2. Culture used, 26-day-old pionnotes on stem of 

 Melilotus alba. 



F. -vasinjechim 3167; reisolation of 1855, on June 19, 191 4, from Idaho 

 Rural potato in above experiment, after 25 days' incubation at 25.5° 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° 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° 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 cot ton- 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° 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° 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 Verticillium 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. 



