10 
Journal oj Agricultural Research 
Vol. XXX, No. 1 
INHERITANCE OF SPIKELET 
CHARACTERS 
In reviewing the literature on the 
inheritance of particular characters in 
oats it has been thought best to sum¬ 
marize the results under the heads of 
the various characters studied in the 
Burt oat. These were (1) spikelet 
disarticulation, (2) floret disjunction, 
(3) basal hairs, .(4) awns, and (5) lemma 
color. 
SPIKELET DISARTICULATION 
At maturity or in threshing the oat 
spikelet becomes detached from the 
pedicel on which it is borne. (Its mor¬ 
phology is discussed more fully later 
in this paper.) In different species 
and varieties this disarticulation of the 
spikelet occurs in somewhat different 
ways, which result in very different 
appearances of the tissues at the base 
of the lower floret or kernel. 
According to Etheridge (33) the 
basal form of the oat grain has been 
little used in classifying oat varieties. 
He states that the callus, the some¬ 
what swollen tissue at the base of the 
lemma, is an insignificant part of the 
oat grain. There is sufficient reason 
for believing that the character of 
basal form in the oat kernel is of more 
importance than his statement would 
indicate. The terms “sucker-mouth,” 
horseshoe base, basal scar, cicatrice, 
and others have been used by various 
writers to describe the thickened in¬ 
durated tissue at the base of the kernel 
which here is termed the callus. 
Surface (137), Love and Craig (70), 
and Fraser (37) have studied the in¬ 
heritance of the form of the base. The 
results obtained by all of these investi¬ 
gators indicate the dominance of the 
absence of basal scar, characteristic of 
Avena sativa varieties, over its presence, 
as exhibited by Avena fatua, Avena 
sterilis, and the cultivated varieties of 
the latter which here are grouped as 
Avena byzantina. 
The writers have found this char¬ 
acter to be of considerable interest, as 
in its genetic behavior it is one of the 
most constant of the kernel characters 
studied. 
Etheridge (33) cites Denaiffe and 
Sirodot (26) as having characterized 
various forms of the base according to 
the obliquity of the scar produced by 
the detachment of the lower floret from 
its pedicel, but these authors do not 
relate the form of the base to the more 
definite character of articulation or 
nonarticulation. Bohmer (9) and (10) 
also mentions several forms of the base 
of the lower floret, but does not use 
them in his classification. Trabut 
(135) makes but little use of the basal 
form in his paper on the Origin of 
Cultivated Oats. 
Surface (127) reports the results 
obtained from crosses between Avena 
fatua and Avena sativa, variety Kher¬ 
son. He states that the wild form 
showed an expanded oval ring at the 
base of the lower floret and that in the 
cross with Kherson the basal form 
showing no scar (sativa) was dominant, 
or nearly so. He found the following 
characters correlated with the “wild” 
type of base on the lower grain: (1) 
“Wild” base on the upper grain; (2) 
very heavy awns on the lower grain of 
every spikelet; (3) very heavy awns 
on the upper grain of every spikelet; 
(4) heavy pubescence on the pedicel of 
the lower grain; (5) heavy pubescence 
on the pedicel of the upper grain; (6) 
heavy pubescence on all sides of the 
base of the lower grain; (7) heavy pu¬ 
bescence on all sides of the base of the 
upper grain. 
Surface (127) detected exceptions to 
the linkage, or crossovers, between the 
factors for pubescent glumes and black 
glumes (about 0,7 per cent) and the in¬ 
hibitor of glume pubescence and the fac¬ 
tor for “cultivated” base (about 1.5 per 
cent). Bartlett (8) has reviewed the work 
of Surface, above cited, on linkage and 
crossing over in oats. He believes that 
some of the cases considered as linkage 
by Surface (127) can be interpreted in 
a simpler manner. For instance, if the 
first floret is awned, it is a fair assump¬ 
tion that the second is potentially the 
same, even though its position be such 
that manifestation of the character is 
a physiological impossibility. He sug¬ 
gests that a factor linked with the 
factor for cultivated base may be con¬ 
ceived as a partial inhibitor of the 
pubescence factor. 
Wilds 11 found, in crosses between 
Avena fatua and cultivated varieties of 
Avena sativa, that the character of the 
base is determined by a single pair of 
genes, the sativa type being dominant. 
The fatua base showed perfect linkage 
with the factors for strong awns and 
dense basal pubescence. 
Love and Craig (70), in crossing 
Avena fatua with Avena sativa, variety 
Sixty-Day, found that in the segrega¬ 
tion of the F 2 generation the sativa-like 
form of base is dominant or partially so. 
11 Wills, G. J. inheritance of glume characters in avena. 1917. I Unpublished thesis, Cornell 
Univ., Dept. Plant Breeding.] 
