Feb. 15,1925 Smut Susceptibility of Selections from an Oat Hybrid 389 
SMUT INFECTION AT BROOKLYN IN 1922 
As noted previously, F 4 plants were 
grown at Brooklyn from seed harvested 
from the F 3 rows of the 1919 sowings, 
although no attempt was made to 
grow plants from a single F 3 parent. 
F 3 plants from the F 4 generation of 
1920 also were grown. Separate sets 
of seed were inoculated with Ustilago 
avenae and U. levis. The results from 
U. avenae were much lower than might 
be expected. However, all the results 
obtained with this smut during that 
season were unusually low and a partial 
explanation is that the spores used 
showed much poorer germination than 
those employed in previous seasons. 
However, the results with U. levis in 
the general varietal experiments also 
were somewhat below those of previous 
years, indicating that the season was 
not especially favorable for these 
smuts. 
In general, however, the F 3 families 
which had previously shown high 
susceptibility showed the highest in¬ 
fections in 1922, and the very resistant 
F 3 families showed very low infections 
or entirely negative results. In many 
cases, negative results were obtained 
with F 4 plants derived from moder¬ 
ately resistant F 3 families. The re¬ 
sults, however, are in harmony with 
those previously obtained. The evi¬ 
dence also indicates that the selections 
react in a similar fashion to both smuts. 
Selections highly resistant to one smut 
also are resistant to the other, and 
selections highly susceptible to the one 
are susceptible to the other. In some 
cases the percentage of infection with 
Ustilago levis was too low, but the data 
obtained are not sufficient to prove 
whether or not there are cases in 
which the susceptibility of a selection 
to the two smuts is different. 
RELATIONSHIP OF PLANT CHARACTERS 
TO SMUT RESISTANCE 
The data on certain spikelet charac¬ 
ters of the F 2 plants shown in Table I 
apparently indicate that no definite 
relationship or correlation exists be¬ 
tween morphological characters and 
resistance or susceptibility to these 
smuts. (See pi. 4.) 
With regard to the presence and 
absence of awns, it will be seen that 
smut resistance is not confined to those 
families in which the parent F 2 plant 
was either fully awned or practically 
awnless. Of the 12 F 2 plants producing 
immune or very resistant progeny, 7 
were described as having abundant 
awns, 1 as being commonly awned, 
and 4 as having few awns. On the 
18952—25t- 7 
other hand, of the 36 F 2 plants pro¬ 
ducing moderately susceptible or very 
susceptible progenies, 24 were placed 
in the abundantly awned class, 7 in the 
commonly awned class (approximately 
50 per cent of spikelets awned), and 5 
in the class with few awns. 
The disjunction of the second floret 
is discussed in terms of the disarticula¬ 
tion of the rachilla segment in sativa 
and its permanent attachment to the 
floret in sterilis. The 12 F 2 plants 
producing immune or very resistant 
progenies were classed as follows: 2 
attached (Fulghum), 10 intermediate, 
and none disarticulated (Swedish 
Select). The classification of the 36 
F 2 plants producing moderately sus¬ 
ceptible or very susceptible progenies 
was as follows: 9 attached (Fulghum), 
5 disarticulated (Swedish Select), and 
22 intermediate. 
On the basis of lemma color the 12 
F 2 plants that produced immune or 
very resistant progenies, were de¬ 
scribed as follows: 1 reddish-yellow, 4 
yellow, and 7 yellowish-white. The 
36 plants producing moderately or very 
susceptible progenies were represented 
as follows: 6 reddish-yellow, 21 yellow, 
9 yellowish-white. 
It thus will be seen that no definite 
correlation appears to exist between 
morphological characters and smut re¬ 
sistance or smut susceptibility. Fur¬ 
ther evidence supporting this indication 
is shown by data recorded on the F 3 
progenies from certain of the above 
very resistant and moderately suscep¬ 
tible or very susceptible plants which 
were grown in agronomic nurseries to 
determine their uniformity and general 
vigor. 
For example, it was observed that, 
of the 14 plants grown from F 2 plant 
No. 1015al-12,6 resembled the Fulghum 
parent and 8 the Swedish Select parent 
in most characters, thus showing the 
genetic segregation of morphological 
characters. A similar observation was 
made on the F 3 progenv from plant 
No. 1015al-33. The data in Table I 
show that the percentage of smut in 
both the F 3 and F 4 progenies from the 
plant No. 1015al-12 was zero. No 
smut was present in the F 3 generation 
of plant No. 1015al-33, but in the 
F 4 and F 5 , 2.9 and 0.8 per cent, respec¬ 
tively, of the plants of one F 3 selection 
were infected. In the F 3 generation 
2 per cent of the plants from another 
F 3 selection of plant No. 1015al-33 were 
infected with Ustilago levis. 
Under the environment of Aberdeen, 
Idaho, the Fulghum variety produces 
rather short culms, but the Swedish 
Select oat grows much taller. As a re- 
