Hayes and Garber - Cucurbit Breeding

RESULTS OF SELECTION WITH SELF-FERTILIZED CROPS 127
characters of the stems of cereals has been carried out at the
Minnesota Station (Garber and Olson, 1919). Number of fibrovascular
bundles, area of sclerenchyma cells in the cortex and
bundle and other characters were studied in relation to lodging.
Stiffness and thickness of wall of the sclerenchyma seemed to be
associated in oats but no such relation was found in wheat and
barley. No other instance of a close association between any
one of the characters studied and lodging was obtained.
Some correlations are of value in selection or in obtaining
accurate data. Thus, if one desires to classify a number of
selections according to comparative maturity,
reliable results
may often be obtained by taking such notes as date of awn emergence
in barley and date of heading in wheat and oats. In years
favorable for normal development, a high correlation between
date of heading and maturity has been obtained. In unfavorable
years, date of heading is a more reliable indication of the inherited
differences between strains in relation to their normal period
of maturity than a note taken at maturity.
In general, it seems safe to conclude that no one character
is closely enough associated with yield to be of selection value
in picking out the highest yielding strain. It is possible, however,
in many crops to weed out the very undesirable plants by
The yield test must then be used to determine the
inspection.
better pure
lines. This seems reasonable when we realize that
yield is the final result of many growth characters. A strain which
excels in all characters, such as stooling, disease resistance, size of
seed, size of head, fertility, etc., naturally will be a high yielder.
As so many characters of which the above are only a few of the
more easily seen are essential to high yield, no single botanical
character is of great selection value.
This has led to the present
method which is summarized as follows by Newman (1912):
"Thus instead of basing the isolation of superior individuals purely
upon botanical or morphological characters as was formerly the case,
the principle has become to select a large number of individuals without
special regard to such characters."
The value of these individuals is determined by the study
of yield continued over several years.
Numerous experiments have proved the value of this method.
In this connection it is of interest to point out progress that has
already been made with self-fertilized crops.