CLASSIFICATION AND INHERITANCE IN WHEAT 81 



Spike Density. Compactness of spike, color of seed and 

 chaff, texture of seed, and presence or absence of awns are fre^ 

 quently used in wheat variety classification. 



Nilsson-Ehle (19116), in crosses between compact and square- 

 head (mid-dense) wheats, obtained compact forms in FI and 

 segregation into compact, mid-dense and lax in F z . He explained 

 the results by supposing the main factor differences to be as 

 follows; 



Swedish Binkel (compact) CCLiLiL 2 Z/ 2 

 Squarehead c 



The C factor was considered to inhibit the expression of the 

 lengthening factors L\ and L 2 , and also to produce spikes with 

 short internodes. While these factors gave a satisfactory 

 explanation of his crosses Mayer Gmelin (1917) showed that they 

 did not explain the production of compact spiked forms which he 

 obtained from crosses of spelt (lax) and Essex Velvet Chaff, 

 which is mid-dense. In F% generations grown from individual 

 plants of a cross between white spring emmer and Marquis, 

 studied at the Minnesota Experiment Station, a very common 

 sort of segregation was from lax, keeled, speltlike wheats to 

 compact, keelless, naked wheats. This might indicate that 

 spelt wheats contain a compact factor which is prevented from 

 expression by some other genetic factor. 



Crosses between T. compactum and T. vulgare by Spillman 

 (1909) and Gaines (1917) have shown one main factor difference 

 for compactness. Parker (1914) made careful measurements of 

 internode length in crosses of wheats belonging to T. compactum 

 with those of T. vulgare. He was able to demonstrate segregation 

 but found the condition very complex. Results of this nature 

 have been satisfactorily explained by the multiple factor hy- 

 pothesis. The number of factors involved cannot accurately 

 be determined. Nilsson-Ehle, likewise, states that besides the 

 main factor differences there are other minor factors which 

 influence spike density and account for a wide range of homozy- 

 gous forms. 



Seed Characters. Color of seed, which results from a brown- 

 ish, red pigment in one of the bran layers (remains of nucellus) 

 has been quite consistently used in variety classification. This 

 is a plant character and not, therefore, immediately affected by 

 pollination. Red is dominant over white and in the second 



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