Nov. I, igis 



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 Wollmw.; F. culmorum (W. G. Sm.) Sacc. (syn., F. rubiginosum App. and Wollenw.); 

 F. trichothecioides Wollenw.; and F. incarnatuvi (Rob.) Sacc.] 



1. Fusarium discolor, var. sulphureum (Schlecht.) App. and Wollenw. (i, p. 115-118). 

 F. discolor, var. sulphureum, is morphologically the same as F. discolor App. and 



Wollenw. (i, p. 114). Normal conidia (PI. XIV, fig. 6) 3- to 5-septate, 23 to 39 by 

 4.5 to 5.5M (limits: 16 to 48 by 3.5 to 6ix); exceptionally i- and 2-septate. True 

 chlamydospores are rare. Conidial masses ocherous to ocherous-orange . Differs from 

 F. 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: (i) The comma type, formed as a slightly ciu-ved 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 ' 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 

 imder 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 



(i) 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- 

 oxysportim, 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. 



