May 1, 1925 
Taxonomic Studies of Fusarium 
839 
Table I.— Culture media showing types of growth readily produced on each. a 
Media 
Onnirlia Chlamy- o plprfttin Myce- 
conidia 1 dospores bcierotia lium 
Color 
Potato tuber cylinders (no water added)_ 
Oatmeal agar (Sherbakoff (5)) . _ _ 
+ + 
+ + 
4- 
+(basic) 
-(-(basic) 
-(-(basic) 
4 -(acid) 
Color of spores 
Color of spores 
Color of spores 
Potato agar 4-2 per cent dextrose (200 gm. to 
1,000 c. c.) 
Potato agar+5 per cent dextrose (200 gm. to 
1,000 c. c.) 
Rice 12 em. to0 c. c. water) 
+ + 
+ _ 
+ ■ 
+ j + 
4- _ 
4* 
Melilotus stems (mature stems4-4 c. c. water') -i- 4- 
+ _ 
Lupinus stems (mature stems+4 c. c. water) 1... 
Alnus (2 to 3 vear twies+4 c. c. water! 
+ _ 
4- __ 
4- _ 
, 
1 
° All agar media contains 2 per cent agar. All media are autoclaved for 45 minutes at 10 pounds pressure 
except rice, which is steamed for one hour on three successive days. When necessary to use young Melilotus 
stems, 4 c. c. of a 0.5 per cent KOH solution should be used in place of water to neutralize the acidity of the 
stems. 
In general, the use of several vegeta¬ 
ble media, such as those mentioned 
in the table, will result in the pro¬ 
duction in good condition of the 
various characteristics of the fungus. 
In some cases special methods must be 
employed for the production of certain 
phases. The addition of acid to the 
standard potato agar greatly stimulates 
an abundant porduction of normal 
spores in such species as the Fusarium 
stage of Gibberella saubinetii (Mont.) 
Sacc. Substances poor in food value 
favor the production of chlamydospores. 
In species which produce chlamydo¬ 
spores only rarely, as F. aurantiacium 
(Lk.) Sacc., chlamydospore develop¬ 
ment may be brought about by 
growing in sterile tap water. The 
reaction of the medium is important 
from the standpoint of color production 
and, in some cases, greatly influences 
growth of mycelium and abundance 
of spore production. 
In transferring, it must be borne in 
mind that the type of inoculum 
influences the resultant growth. Con¬ 
tinuous transfer of one type of in¬ 
oculum tends to production of that 
type of growth. Repeated transfer 
of mycelium or chlamydospores tends 
to good development of mycelium and 
sclerotia in those species which have 
sclerotia. For production of abundant 
spores, transfers should be made 
from sporodochia or pionnotes. When 
sporodochia are lacking and macro¬ 
spores are not numerous, the chance of 
transferring mycelium may be elimi¬ 
nated by making dilutions in tubes of 
sterile water and transferring a loop 
full of the dilution to the culture 
medium, or by using the plate dilution 
method. The latter method affords 
an opportunity to select colonies 
showing the greatest tendency toward 
spore production. 
Environmental factors other than 
the medium which should be taken into 
consideration are temperature, humid¬ 
ity, and light. There are indications, 
in some species at least, that tempera¬ 
ture has an appreciable effect upon the 
morphology of the conidia as well as 
upon the rate of growth of mycelium 
(4). Perhaps to temperature may also 
be ascribed part of the effect on color 
intensity usually attributed to light. 
Humidity affects the nature of the 
culture, as is evidenced by the increased 
production of chlamydospores in some 
species and the production of swollen 
conidia in excessively moist media. 
The fact that these environmental 
factors have been given very little con¬ 
sideration in identification of Fusaria 
may be responsible for some of the 
difficulties encountered in various coun¬ 
tries where taxonomic work is done. 
IDENTIFICATION 
If we realize the fact that tubercular 
sporodochia with normal and uniform 
conidia occur in the majority of Fusaria 
that can be easily grown in pure cul¬ 
ture, there will be no difficulty in 
judging the normal stages and, con¬ 
sequently, in identifying most of these 
fungi. For the remaining forms more 
detailed studies will have to be con¬ 
ducted in order to produce or prove 
the absence of particular stages such 
as sporodochia, pionnotes, chlamydo¬ 
spores, and sclerotia. It should be 
stated also that even conidia normal 
in appearance often differ greatly in 
their size and shape according to where 
they are produced, whether on mycel¬ 
ium’ over a wet surface or in a definite 
sporodochium. In a typical pion¬ 
notes long conidia may be produced, 
and in sporodochia they may be con¬ 
siderably shorter, as in F. vasinfectum 
Atk., F. cubense Erw. F. Sm., F. 
lycopersici (Sacc.) Wr., and others. 
Differences in size and shape may also 
appear when the fungus is grown on 
