Hayes and Garber - Cucurbit Breeding

CLASSIFICATION AND INHERITANCE IN WHEAT 79
concluding that the cultivated emmer and spelt groups arose
from different wild stem species. It is also essential to point out
that all crosses between the cultivated naked emmer wheats with
naked wheats belonging to the spelt group are not entirely fertile.
Indications of partial sterility are generally apparent
if the results
are carefully analyzed (Kezer and Boyack, 1918) (Freeman, 1919)
(Hayes and others, 1920).
Polonicum Crossed with Other Species. Crosses between
polonicum and other forms have been studied. Tschermak
(1913), in a cross between polonicum and vulgare, explained the
results by two main factor differences. The FI was of intermediate
glume length and in F^, polonicum, durum, and vulgare
forms were obtained as well as intermediates. Pure polonicum
was considered to contain two dominant factors in the homozygous
condition; durum, one dominant factor pair in the homozygous
condition; and the pure vulgare forms, both factors in
the recessive condition.
Polonicum (Backhouse, 1918) crossed with durum or turgidum
gave intermediate glume length in ^i and segregation in
F z in a ratio of 3 longs and intermediates to 1 short. Biffen
(1916) and Backhouse in separate studies considered the factor
for polonicum glume to inhibit chaff pubescence and color.
In a
cross between durum (Kubanka) with a polonicum variety, the F*
segregated for glume length and hairy chaff. The short-glumed
plants were in a ratio of 3 hairy to 1 smooth, while the longglumed
plants were difficult to classify for condition of chaff.
Crosses of different long-glumed plants with other wheats showed
that a part of these long-glumed wheats contained a genetic
factor for hairy chaff. Results were explained on the hypothesis
that the factor for long glume partially inhibited development
of hairy chaff. Similar results were obtained by Biffen (1916),
for inhibition of glume color by the polonicum factor for glume
length.
Some Linkage Results in Wheat Crosses. In crosses between
the different species some evidences of linkage have
been observed. In turgidum-vulgare crosses, Biffen (1905) obtained
complete linkage of gray color of glumes with hairy chaff.
Engledow (1914) crossed a black-glumed wheat obtained from a
turgidum-ftfe cross with a rough-chaffed, white-glumed variety,
Essex Rough Chaff. The ratio obtained in F% was explained on
the basis of repulsion between the factors for black glume color