Hayes and Garber - Cucurbit Breeding

MAIZE BREEDING 189
in the factor V, for variegated,
concluded:
to S for self-color. Emerson
"That these results favor the idea that single allelomorphic factors,
rather than two or more closely linked factors, are responsible for the
color pattern of both glumes and pericarp."
The concluding paragraph of Emerson's 1917 paper
is directly
in line with the ideas which have been developed throughout
this book. With most plant-breeding material of our farm
crops, there is no evidence for basing a system of plant improvement
upon mutations, as these are infrequent. With anthocyan
color characters of corn, inherited changes sometimes occur
more frequently and such mutations become of selection value.
This does not invalidate the pure-line conception for the large
number of cases where factor stability is the rule. To quote
from Emerson:
"The existence of the series of at least nine or ten multiple allelomorphs
to which variegation belongs, indicates that a factor for pericarp
color has mutated several times. Some of the factors for this series
have not been observed to mutate, while others have mutated rarely
and still others many times. In fact, the principal difference between
certain of the factors is thought to lie in their relative frequencies of
mutation."
Podded Condition. The podded character was thought by
East and Hayes (1911) to be a simple dominant and to be dependent
on a single factor for its development. Extracted
recessives bred true to the podless condition. Collins (1917)
has presented evidence which indicates that the ordinary type
of tunicate maize represents a case of imperfect dominance and
that it, like the Andalusian fowls, is unfixable and related to the
heterozygous condition. Selfed seeds of typical podded ears produced
three types of plants: (1) like the parent; (2) with normal
ears; (3) a plant which does not produce seed in the lateral inflorescences
but in perfect flowers in the tassels. Jones and
Gallastegui (1919) obtained similar results. A starchy tunicate
ear was used as the female parent and was pollinated with pollen
from a non-tunicate sweet race. The linkage between the
starchy and tunicate factors was quite close,
only 8.3 per cent.
of .
crossing-over occurring.
Auricle and Ligule. Emerson has shown that the absence of
auricle and ligule is a recessive character. In a cross between a