RACE DIFFERENTIATION IN CEREAL RUSTS 75 



Table 7. Seedling reaction of wheat variety Lee to 13 races 

 of stripe rust under differing environmental conditions 











Conditions 







Race 



Lit. a 



22/16 b 

 3000 



22/16 b 

 1000 



17/13 b 



3000 



Green- 

 ly c 



house 



60 







II 



0+ 



O-II 







1 







O-II 



II-IV 











54 







O-II 



II-IV 



0+ 







42A 



IV 



IV 



IV 



IV 



IV 



20A 



IV 



IV 



IV 



IV 



IV 



27/53 







II-IV 



O-II 



O-II 



0+ 



2 











II- 







0(+) 



3/55 







II- 



0-IV 



0+ 







32 A 



IV 



IV 



IV 



IV 



IV 



32 







II-IV 



II-IV 



0+ 



0(+) 



26 











II-IV 











7 







II- 



O-IV 



-- 



0+ 



15 











0-IV 







0(+) 



Indicates the combined results of thousands of greenhouse tests. 



Temperature in degrees C/photoperiod in hours; light intensity 

 in lux. 



Temperature 17°C±2°; light intensity 4000 up to 14,000 lux. 



We see that environmental factors must also be controlled if dif- 

 ferential variations are to give reproducible results. 



Person, Samborski, and Forsyth (1957) reported on the use of 

 detached leaves for race differentiation. In spite of good results in 

 mildew race identification (Wolfe, 1967; Plate and Fischbeck, 1969) 

 cereal rust investigators have dropped this method since susceptibility 

 was much higher in detached leaves than in leaves in their natural 

 connection with the plant (Browder, 1964; Samborski, Forsvth, and Person 

 1958). 



