Hayes and Garber - Cucurbit Breeding

CHAPTER VI
CLASSIFICATION AND INHERITANCE IN WHEAT
Studies of genetics have led to the adoption of a particular
meaning which is understood when we speak of an inherited
character. It is the final result of the interaction of many
inherited factors plus the environment. The factors are the
inheritance and the ultimate character is the manner of reaction
under the special growing conditions to which the organism is
subjected. What is inherited is the ability to react in a particular
manner in a given place and not the character itself.
Genetic Classification.
Classification of cultivated varieties of
crops is made in much the same manner as the botanical classification
of wild species. With crops, there is as a rule considerable
experimental evidence of genetic relationship. The ultimate
aim of crop classification should be genetic in order that it may be
of greatest value. Closeness of relationship as determined by
the ease of crossing and the degree of sterility is frequently made
the basis of species groups in some crops. In other crops no
sterility is obtained in so-called species crosses. Only relatively
stable characters which are not easily modified under different
environmental conditions are
value.
considered of major classification
After placing cultivated crops in groups which are roughly
analogous to botanical species, the next step is more clearly
to separate different categories of a lower order of classification.
These are the varieties. Varieties are not necessarily genetic
entities but may be groups of similar forms which resemble each
other more than individuals belonging to another variety. All
members of a variety are similar to each other in major botanical
characters.
Such a variety classification is of utmost importance. In the
past the variety studies made in the United States by the different
experiment stations or the federal Department of Agriculture
have not always been comparable, as the same name has been
used to refer to widely different varieties. More dependable results
can only be obtained by the adoption of uniform variety names.
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