Nov. i, 1915 
Potato Tuber-Rots Caused by Fusarium Spp. 
207 
C. SECTION DISCOLOR 
[Species in this section are F. discolor App. and Wollenw.; F. discolor , var. sulphureum (Schlecht.) 
App. and Wollenw.; F. culmorum (W. G. Sm.) Sacc. (syn.» F. rubiginosum App. and Wollenw.); 
F. trichothecioides Wollenw,; and F. incarnatum (Rob.) Sacc.] 
1. Fusarium discolor, var. sulphureum (Schlecht.) App. and Wollenw. (1, p. 115-118). 
F. discolor , var. sulphureum, is morphologically the same as F. discolor App. and 
Wollenw. (1, p. 114). Normal conidia (PI. XIV, fig. 6) 3- to 5-septate, 23 to 39 by 
4.5 to 5.(limits: 16 to 48 by 3.5 to 6 m); exceptionally 1- and 2-septate. True 
chlamydospores are rare. Conidial masses ocherous to ocherous-orange. Differs from 
F t discolor in the color of the plectenchymatic mycelium, which never becomes 
carmine-red (PI. B.), but changes from ocherous to yellow (egg-yellow to sulphur- 
yellow, which color permeates the aerial mycelium and conidial masses). 
Habitat.—In hollows of potato tubers. Established by Dr. Wollenweber as the 
cause of a tuber-rot in Germany. It was isolated from decaying tubers from Newell, 
S. Dak., and identified by Dr. Wollenweber. The writer also identified it in similar 
material from Cresbard, S. Dak., and in tubers from the North Dakota Agricultural 
College (collected by Mr. D. G. Milbrath). 
2. Fusarium trichothecioides Wollenw. (5, p. 146-152). 
F. trichothecioides , in contrast to the other species of the section Discolor, forms two 
sorts of conidia: (1) The comma type, formed as a slightly curved comma ellipsoidally 
rounded on both sides; and (2) the normal macroconidia, typical of the section. The 
plectenchymatic mycelium and conidial masses are rosy white, in contrast to the 
carmine 1 mycelium in F. discolor (PI. B, fig. 1-3) and the ocherous-yellow mycelium 
in F. discolor , var. sulphureum (PI. B, fig. 4-6). The conidial masses in both the last- 
named species are ocherous orange. 
Habitat.—Dry-rotting tubers of Solatium tuberosum , causing decay, especially 
under storage conditions. Geographic distribution: Spokane, Wash.; St. Paul, 
Minn.; Dayton, Iowa; Alliance, Nebr.; Spearfish, S. Dak. (Jamieson and Wollen¬ 
weber). The following localities are added to the above: Jerome and Idaho Falls, 
Idaho; Newell, S. Dak.; and Sioux City, Iowa. 
SUMMARY 
(1) A new stem-end and wound-invading dry-rot of the Irish potato 
annually causing serious damage in Pennsylvania is caused by a species 
of Fusarium for which the name “Fusarium eumartii” is proposed. 
(2) Another widely prevalent dry-rot similar to the above is caused 
by F. radicicola Wollenw. 
(3) F. radicicola and F. oxysporum are most commonly associated 
with the so-called “jelly-end” rot, annually a serious trouble in the 
tule lands of California. The former seems to be the cause in most 
cases, but the fundamental relationship of F. oxysporum to this and other 
tuber-rots should not be overlooked. 
(4) Experimental inoculations show that F. oxysporum and F. hyper - 
oxysporum , species of the section Elegans, which has been reported as 
containing purely vascular parasites, are capable of entirely destroying 
potato tubers. 
(5) F. oxysporum is the cause of certain types of tuber-rot. 
1 Jamieson and Wollenweber (5) give “ purple ” mycelium through error. 
