CLASSIFICATION AND INHERITANCE IN WHEAT 87 



disease causes an annual decrease of 15 per cent, in the yield of 

 winter wheat in the States of Washington, Oregon, and Idaho. 



The method used in studying bunt resistance was to blacken 

 the seed with smut spores just before planting and then sow the 

 strains and crosses in rows in such a way that each plant could 

 be individually examined. 



Studies of inheritance were made in crosses of Turkey X Flor- 

 ence and Turkey X Hybrid 128. Hybrid 128 is a prolific, 

 winter-hardy, stiff-strawed wheat of much commercial value 

 but it is very susceptible to bunt. Turkey does not yield as well 

 as Hybrid 128, has weak straw, and shatters considerably. It is 

 highly resistant to bunt. Florence is an Australian spring wheat 

 which is highly resistant to bunt. 



The results presented by Gaines show very clearly that resist- 

 ance to bunt is an inherited character. However, several factors 

 are necessary to explain the sort of segregation obtained. The F z 

 of the cross between Florence and Turkey showed transgressive 

 segregation. In F s , 171 families were grown from individual F 2 

 plants. Of these, 72 were immune while 50 families produced over 

 80 per cent, of bunt. The Turkey and Florence parents under 

 the same conditions produced an average of 4.6 per cent, of 

 infected plants. This shows that the factors for resistance in the 

 Florence and Turkey varieties are not identical. 



In the cross between Turkey and Hybrid 128 no segregates 

 were obtained with a higher degree of resistance than the Turkey 

 parent. It was found possible to produce resistant strains of 

 any morphological type desired. 



Inheritance of Other Characters. Nilsson-Ehle (1911c, 1912) 

 has shown that winter-hardiness is inherited in much the same 

 manner as other characters. Segregation occurs in F z and types 

 can be produced in later generations which are homozygous for 

 different degrees of winter-hardiness. Crosses made (Hayes and 

 Garber, 1919) in 1902 between hardy Odessa winter wheat and 

 Turkey varieties were bred for several years by continuous selec- 

 tion methods. Odessa is a late maturing variety and does not 

 give a high yield in Minnesota. Turkey is a desirable winter 

 wheat in many sections but it lacks hardiness under Minnesota 

 conditions. Two early maturing wheats, Minhardi and Min- 

 turki, have been produced from the cross between Turkey and 

 Odessa. These new varieties excel in winter-hardiness and 

 yield. 



