Hayes and Garber - Cucurbit Breeding
Hayes and Garber - Cucurbit Breeding Hayes and Garber - Cucurbit Breeding
98 BREEDING CROP PLANTS gous forms are less heavily awned than the false wild and have the fatua type of callus only on the lower grain. Considerable difference of opinion is held regarding the cause of the production of false wild oats. Whether they originate as a loss mutation or through hybridization or both is not yet determined. Some evidence for hybridization and some for mutation has been obtained. CLASSIFICATION AND INHERITANCE IN BARLEY Students of barley classification have frequently used density and sterility of the lateral florets as chief means of separating the larger cultivated groups. While density is quite a stable character, there are gradations in the length of the internode from the very lax to the very dense spikes without any clear-cut differentiation between the mid-dense and mid-lax groups. While density is an important character by means of which to differentiate forms, it is not very usable as a chief means of group classification. Harlan (1918) has made an interesting review of barley classification studies and has presented a new grouping in which species are made on the basis of fertility of the lateral florets. The following key is taken from Harlan's paper : All spikelets fertile (six-rowed barley) Lemmas of all florets awned or hooded Hordeum vulgare L. Lemmas of lateral florets without awns or hoods .. .H. intermedium Kcke. Only the central spikelets fertile (two-rowed barley) Lateral spikelets consisting of outer glumes, lemma, palea, rachilla, and usually rudiments of sexual organs H. distichon L. Lateral spikelets reduced usually to only the outer glumes and rachilla, rarely more than one flowering glume present and never rudiments of sexual organs # deficiens Steud. There are several contrasting characters by means of which variety groups are made. Harlan has used the following to differentiate the variety groups belonging to each of the four species groups: Seeds hulled; seeds naked. Lemmas awned; lemmas hooded. Seeds white, blue, purple; seeds black.
CLASSIFICATION AND INHERITANCE OF SMALL GRAINS 99 In classifying the cultivated varieties of barleys, the density of the spike, its shape, and the appearance of the awns as well as the color of the seed, have been used. Smooth-awned varieties are being produced and it is only a question of time before nearly all awned varieties will be represented by both the rough and smooth-awned forms. Species Crosses. Two general results have been obtained from crossing two- and six-rowed varieties. The most frequent result is an intermediate condition in FI in which the lateral florets are awned, but produce little or no fruitfulness. In F 2 a 1 : 2 : 1 ratio of six-rowed, intermediate, and two-rowed forms is obtained. Six-rowed and two-rowed forms breed true to these respective characters in later generations. Results of this nature can easily be explained on a single main factor difference (Biffen, 19076; Gaines, 1917). The intermedium barleys have generally been considered to be of hybrid origin. A cooperative study carried on at the Minnesota Experiment Statioa has shown the probable origin of some intermedium forms (Harlan and Hayes 1920). In a cross between Manchuria, a six-rowed barley, and Svanhals, a two-rowed variety, the F\ was slightly fruitful and produced intermediate developed awns on the lateral florets. In F 2 a wide range of forms was obtained. The genetic nature of the F 2 plants was determined by growing seed of each in F 3 . From the F 3 results it was possible to classify F% plants as follows : 1. Those that bred true for the six-rowed character. 2. Those that segregated, giving six-rowed, awned intermediate forms with very high fruitfulness of the lateral florets and intermedium, forms in a 1:2:1 ratio. 3. Intermedium forms that bred true, giving few or no awns on lateral florets and producing approximately 50 per cent, of barren lateral florets. 4. Those that gave all forms as in F-z. 5. Those that produced intermediates and tw r o-rowed types. 6. Those that produced six-rowed, awned intermediates with little or no fruitfulness in the lateral florets and two-rowed forms in a 1:2:1 ratio. 7. Those that bred true for the two-rowed condition. Results were accurately explained by considering the Manchuria parent to contain two factors, one for six-rowed and one for intermedium, which was hypostatic to the six-rowed factor. It
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98 BREEDING CROP PLANTS<br />
gous forms are less heavily awned than the false wild <strong>and</strong> have<br />
the fatua type of callus only on the lower grain. Considerable<br />
difference of opinion is held regarding the cause of the production<br />
of false wild oats. Whether they originate as a loss mutation<br />
or through hybridization or both is not yet determined. Some<br />
evidence for hybridization <strong>and</strong> some for mutation has been<br />
obtained.<br />
CLASSIFICATION AND INHERITANCE IN BARLEY<br />
Students of barley classification have frequently used density<br />
<strong>and</strong> sterility of the lateral florets as chief means of separating<br />
the larger cultivated groups. While density is quite a stable<br />
character, there are gradations in the length of the internode<br />
from the very lax to the very dense spikes without any clear-cut<br />
differentiation between the mid-dense <strong>and</strong> mid-lax groups.<br />
While density is an important character by means of which to<br />
differentiate forms, it is not very<br />
usable as a chief means of<br />
group classification. Harlan (1918) has made an interesting<br />
review of barley classification studies <strong>and</strong> has presented a new<br />
grouping in which species are made on the basis of fertility of<br />
the lateral florets. The following key is taken from Harlan's<br />
paper :<br />
All spikelets fertile (six-rowed barley)<br />
Lemmas of all florets awned or hooded Hordeum vulgare L.<br />
Lemmas of lateral florets without awns or hoods .. .H. intermedium Kcke.<br />
Only the central spikelets fertile (two-rowed barley)<br />
Lateral spikelets consisting of outer glumes, lemma, palea, rachilla, <strong>and</strong><br />
usually rudiments of sexual organs H. distichon L.<br />
Lateral spikelets reduced usually to only the outer glumes <strong>and</strong> rachilla,<br />
rarely more than one flowering glume present <strong>and</strong> never rudiments of<br />
sexual organs<br />
# deficiens Steud.<br />
There are several contrasting characters by means of which<br />
variety groups are made. Harlan has used the following to differentiate<br />
the variety groups belonging to each of the four species<br />
groups:<br />
Seeds hulled; seeds naked.<br />
Lemmas awned; lemmas hooded.<br />
Seeds white, blue, purple; seeds black.
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