58 



H. K. HAYES 



be used according to the viewpoint of the breeder and the particular prob- 

 lem to be solved. 



While combining ability is an inherited character, it seems of special in- 

 terest that single crosses of high X high combiners have not been greatly su- 

 perior in yield, on the average, to crosses of high X low. Both, however, were 

 clearly higher in yielding ability than low X low crosses (Johnson and 

 Hayes, 1940), (Cowan, 1943), (Green, 1948). An illustration from Johnson 

 and Hayes (Table 3.8) shows the type of results obtained. The crosses were 

 classified for yielding ability in comparison with recommended double 

 crosses of similar maturity. 



Two recent studies in Minnesota may be used to illustrate other breeding 

 problems. A further study was made by Johnson (1950) of the combining 

 ability of F4 lines that were studied in earlier generations by Payne and 

 Hayes (1949). Yield relations in the double cross Min. 608 (A344 X A340) 

 (A357 X A392) are illustrated in Table 3.9. 



TABLE 3.8 



FREQUENCY DISTRIBUTION FOR YIELD OF SINGLE CROSSES 



OF SIMILAR MATURITY IN COMPARISON WITH 



RECOMMENDED DOUBLE CROSSES AS 



TABLE 3.9 



YIELD RELATIONS IN MIN. 608 



( A334 X A340) (A357 X A392) 



