Hayes and Garber - Cucurbit Breeding

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28 BREEDING CROP PLANTS
The general nature of the results in this field may be illustrated
between barley varieties which differ in the average
by a cross
length of internodes of the rachis (see Table I).
In this cross between Hanna and Zeocriton, lax and dense
varieties respectively, the F 2 ranged from above the modal class
of Hanna to the modal class of Zeocriton even though only 141
individuals were studied. The calculated coefficient of variability
for the F 2 was three or four times greater than for the
parental varieties. Several small F% families were grown from
F 2 plants representing different densities. By examining the
table one will note that some F 3
lines bred comparatively true,
FIG. 8. Average spikes of the Zeocriton (left) , Hanna (right) and four homozygous
lines. Mean densities are as follows: Zeocriton, 1.9 mm.; Hanna X
Zeocriton, 448-1, 2.3 mm.; 448-5, 2.9 mm.; 448-11-3, 3.7 mm.; 448-16, 4.3 mm.;
Hanna, 4.6 mm.
the ranges for density being no greater than for the parental
lines and the coefficients of variability also being low. Other
7< 3 lines were as variable as the F 2 generation while still others
were more variable than the parents but less variable than the F 2 .
Several F 3 lines, which appeared homozygous, were tested in
7^4 and some of these on the basis of the more extensive test again,
gave evidence of homozygosity. The general nature of the
results is illustrated in Fig. 9. These results show that homozygous
lines for density may be obtained in F 3 and F 4 ,
and that
in this cross homozygous lines were obtained which approached
the densities of the parents as well as homozygous lines with