1030 
Journal of Agricultural Research 
Vol. XXVIII, No. 10 
through sterility and that the ultimate homozygous fertile segregates will have 
either 14 or 21 chromosomes ( 10 , 11 ), Segregates with 14 chromosomes re¬ 
semble the emmer parent in most respects while segregates with 21 chromosomes 
possess most of the vulgare characters, indicating that the 7 additional chromo¬ 
somes determine the differentiating characters of the vulgare wheats. 
The elimination of gametes and segregates with an intermediate chromosome 
number would disturb genetic segregation in case of factors located in the 7 
chromosomes contributed by the vulgare parent which do not pair in the reduc¬ 
tion division of F x crosses between emmer and vulgare wheats. Normal Men- 
delian segregation should usually occur with those factors located in the 14 
emmer and vulgare chromosomes which pair in F t hybrids. Thus one might 
expect normal Mendelian segregation of characters common to the two groups 
of wheat species and aberrant segregation of characters which distinguish the 
two groups. Of the characters analyzed in both F 2 and F 3 of such species 
crosses, the presence or absence of awns, yellow or black awns, and red and white 
grain are all characters found in either the emmer group or the vulgare group 
although black awns are rare in vulgare wheats ( 8 , 9 ). The segregation of awn 
length into so-called awnless (tip-awned) and awned is clearly dependent on a 
single factor difference and a normal Mendelian segregation is obtained. The 
segregation of awn color is complicated by the effect of environmental factors 
but F 3 classification indicates a simple Mendelian ratio. The number of segre¬ 
gates with white grain in the cross of Marquis X Alaska would indicate the 
presence of two factors for red color although the number of segregating indivi¬ 
duals is greater than expected. 
On the other hand, the characters which distinguish the emmer and vulgare 
groups apparently do not segregate in a Mendelian fashion, as indicated by the 
data presented in Tables II and III. Most varieties of the emmer group have 
very hard flinty kernels, a large sharp keel on the outer glume and some varieties 
have branched spikes. These characters are found in no vulgare variety. Since 
these characters are common* to all of the varieties in the emmer group it is 
impossible to determine how they are inherited in fertile varietal crosses. There 
is, however, one exception in the case of Alaska. Alaska has the branched spike 
while the durums and emmer wheats have a normal spike. The fact that the 
cross of Alaska X Emmer resulted in an apparently simple ratio of normal and 
branched or at least the genetic behavior is entirely different than in the species 
hybrids. The nonMendelian segregation of these typical emmer characters 
in the species hybrids suggests that they may be dependent on the presence or 
absence of factors located in the extra seven vulgare chromosomes which do not 
pair in crosses with emmer wheat. Since these seven chromosomes are irregularly 
distributed and certain classes are apparently eliminated due to sterility, a 
normal Mendelian segregation would not be expected. 
Certain crosses between members of the vulgare group and members of the 
emmer group are more fertile than others as indicated in Table I. In the more 
fertile crosses segregates may possess certain combinations of parental char¬ 
acters and intermediate chromosome numbers while in the more sterile crosses 
the intermediate types would be rapidly eliminated and the surviving segregates 
would have either 14 or 21 chromosomes and would resemble the parental species. 
Thus there should be considerable correlation or association of the characters 
contributed by each parent in the more sterile hybrids while in the more fertile 
crosses there would be less tendency for the characters of each parent to be 
associated. This is actually the case, as indicated by the correlations presented 
in Table V. These results would indicate that combinations of the characters 
of the emmer and vulgare wheats can be obtained more frequently in the more 
fertile combinations. However, many plant breeders have attempted to com- 
