Hayes and Garber - Cucurbit Breeding

CLASSIFICATION AND INHERITANCE OF SMALL GRAINS 105
standard awned strains. Likewise, many hooded hybrids have
been produced but none has proved satisfactory. The facts
lead to the conclusion that "the awn is an organ that is functional
under most conditions, and especially in those sections
where humid weather prevails, at ripening time." A study of the
effect of the removal of the awns on the development of the seeds
of the spike showed that spikes with awns removed (clipped
spikes) produce a lower weight of dry matter at maturity than
normal spikes. As the seeds develop as rapidly for several days,
after the awn is removed, in clipped spikes as in undipped, the
difference in development at maturity is not due to the shock of
removing the awns. About one week after flowering, the deposit
of dry matter in the normal spikes begins to exceed that in the
clipped spikes. This is stated to be at the time rapid starch
infiltration begins. Normal spikes at maturity, near Aberdeen,
Idaho, have a content of more than 30 per cent, of ash in the
awns. The rachises of the clipped spikes at maturity contained
about 25 per cent, more ash than those of normal spikes, which
probably accounts for the greater tendency of clipped spikes to
break.
These facts show that under humid conditions there is a
physiological reason why awned varieties yield higher than
hooded or awnless varieties. They are given as an illustration
of the value to the plant breeder of a knowledge of the physiological
functions of the various organs of plants.
Two methods of attack are outlined for the barley breeder:
(1) The use of varieties which normally have a low percentage of
ash in the rachis might make possible the production of nonshattering
hooded and awnless sorts. (2) The production of
smooth-awned varieties, which in a large measure, would overcome
the objection to the barley awn.
The production of high-yielding smooth-awned varieties is not
a difficult task, as has been learned by cooperative studies carried
on at the Minnesota Station. As smooth awn is a recessive
character, all that is necessary is to cross high-yielding toothed
varieties with smooth-awned sorts, and then select smoothawned
plants in F 2 . These will breed true for the smooth-awned
character. Numerous plants should be selected, as some will
prove more valuable than others for economic characters such
as yield, non-shattering habit, and stiffness of straw.