Nov. 1, 1915 Potato Tuber-Rots Caused by Fusarium Spp. 197 



F. radicicola 2890 plus Rhizocionia sp. 2892. The two organisms were 

 used in combination, 14 tubers being inoculated and incubated as above. 

 More advanced decomposition seemed to take place than when F. radi- 

 cicola alone was present. However, the species of Rhizoctonia could 

 not be recovered, but F. radicicola was reisolated wherever the attempt 

 was made. 



F. radicicola 3021 ; reisolation of 2890 from a Burbank potato 20 days 

 after inoculation with the latter. With this reisolated strain an attempt 

 was made to ascertain the effect of the temperature factor on the action 

 of the organism. The inoculated tubers (Irish Cobbler variety) were 

 badly decomposed at average temperatures of 23.3°, 20.2°, and 19.5° C. 

 At 18.7° the majority were more seriously affected than at lower tem- 

 peratures; indeed, at 17.5° and 15.1° the effect was a slow dry-rot, while 

 at 12.5° the organism persisted for 88 days without perceptible damage 

 to the host. 



F. radicicola 3023. Another reisolation of strain 2890; from lenticel 

 infection after 20 days' incubation at 23° C. All tubers of the three 

 varieties Netted Gem, Idaho Rural, and People's inoculated with this 

 strain and incubated for 21 days at an average temperature of 25.6° were 

 very badly decomposed. The organism was recovered by three isolations. 



F. radicicola 2998; isolated March, 1 914, from a stem-end ring disease 

 and wound-infected tuber from Fallon, Nev. Culture used, 12-day-old 

 pionnotes on stem of Melilotus alba. All tubers inoculated with this strain 

 and incubated 20 days at 23° C. rotted. The organism was recovered. 



F. radicicola 3236; isolated in August, 1 914, in association with F. hyper- 

 oxysporunt from a soft-rotting tuber from Ocean Springs, Miss. Culture 

 used, I -month-old potato cylinder. The results with this strain are 

 as follows: One tuber incubated for 14 days at 25.7° was badly softened 

 with wet-rot. The organism was recovered. Nine tubers at 24.6° for 

 24 days were sHghtly rotted in every inoculation prick, one tuber being 

 completely softened with grayish wet-rot. Organism recovered by two 

 reisolations. Sixteen tubers incubated 51 days at temperatures ranging 

 from 16.3 to 18.4° C. gave the following results: At lowest temperature 

 no rot occurred, but the organism had become established; two of the 

 four tubers at 17° were rotting slightly, with the organism established 

 in the others; at 17.8°, two were slightly rotted, with the organism 

 persisting in the others; at 18.4° one tuber was sound and the three 

 others were rotting. 



F. radicicola 2862; isolated October, 1913, from jelly-end rot of a tuber 

 of the Burbank variety from Sargent Island near Middle River, Cal. 

 Culture used, 9-day-old pionnotes on stem of Melilotus alba. This strain 

 was comparatively inactive, only 12 per cent of the inoculated tubers 

 rotting after 20 days' incubation at 23° C. The organism was recovered. 

 9838°— 15— 2 



