Hayes and Garber - Cucurbit Breeding

192 BREEDING CROP PLANTS
Studies of the linkage relations of these chlorophyll factors
have been made. The seedling factors w and v, and v and I
show independent inheritance. The factors which influence the
chlorophyll development in the mature plant, g and st, g and
j, g and /, j and st, j and /, appear to be inherited independently.
Also st and v are inherited independently.
The linkage relations suggest that one pair of chromosomes
in maize contains the factor pairs Gg and LI as well as the aleurone
factors, Rr. The japonica striping is influenced by the aleurone
factor R, as the presence of R represses striping, while r allows
full expression of the pattern. These abnormalities have been
discussed in some detail as they show typical Mendelian inheritance
of chlorophyll characters and have considerable
bearing on the improvement of corn by the isolation of pure
biotypes.
Some Seed and Ear Characters. Crosses between dents and
flints were studied by East and Hayes (1911). There is no
immediate visible effect of foreign pollen on the endosperm seed
characters which separate these subspecies.
Segregation occurred
in FZ', some forms were obtained in F 3 which bred true to flint
habit; some bred true to the dent type; while still others
showed segregation. Two or more factors were necessary to
explain results. The inheritance of the pointed condition of
the seed which is characteristic of white rice pop was also studied
by Hayes and East (1915). It was found possible to transfer
this pointed condition to the dent subspecies. Results were
complex and indicated that two or more cumulative factors
were involved.
Size Characters. Emerson and East (1913) summarized
inheritance of size characters of seeds and ears. Weight of
seed, seed measurement, number of rows, and length and diameter
of ear were characters studied. In general, the FI condition
was intermediate, and complex segregation occurred in F 2 .
The inheritance of height of plant, of period of maturity, and of
suckering habit, was also studied. The fact that a considerable
series of fairly stable varieties is known which exhibit numerous
conditions of the development of particular size characters, is also
evidence of a complex inheritance. Segregation occurred in
Fz and extracted forms were obtained which approached the
original parental conditions.
sometimes bred true.
Intermediates, as well as extremes,