CLASSIFICATION AND INHERITANCE IN WHEAT 77 



yielding ability. A knowledge of the mode of inheritance of 

 each of these characters is essential to the rapid purification of a 

 cross. 



It is not desirable in a text on plant breeding to outline variety 

 classifications in very great detail. As a rule the crops student 

 will be familiar with such classifications before studying crop 

 improvement. It seems sufficient to indicate genetic relation- 

 ship and to point out the characters which have been used. 



Wheat Species Groups. From the middle of the last century 

 until the present time numerous crosses between wheat varieties 

 and also between species groups have been made. Extensive 

 crossing studies have led Tschermak (1914 a,b) to conclude that 

 the genetic relationships in wheat areas represented in Table XV. 



TABLE XV. WHEAT SPECIES GROUPS 



Crosses reported by Tschermak between the einkorn and spelt- 

 groups so far have proved wholly sterile, while the einkorn s 

 emmer crosses have proved only slightly fertile. Similar result, 

 have been obtained by other investigators. The crosses between 

 the covered emmer types and the naked and covered spelt forms 

 or between covered and naked forms of the emmer group were 

 partially fertile. Somewhat greater fertility was found in 

 crosses between T. polonicum and the naked wheats of the spelt 

 group, also between naked forms of the emmer group and the 

 covered form of the spelt group. Some of the latter crosses 

 seemed wholly fertile. Crosses belween naked wheats proved 

 wholly fertile. 



Vilmorin (1880, 1883) concluded that spelt and common wheats 

 belong to one group and durum and turgidum to another, for 



