70 



EVA FUCHS 



the years we became aware of a race group (20A) occurring on Mediterranean 

 samples. Since this race group was a problem in the Mediterranean, a 

 differentiation was necessary. Utilization of a variety believed to be 

 resistant to race group 20A provided the differentiation. Local varieties 

 or varieties from neighboring countries should be tested intensively. 



Names and numbers of races don't say anything, if they are not 

 connected with applied genetical knowledge. Last year we received many 

 samples from Israel and by luck we were able to find three different 

 races within the 20A race group by using the "resistant" wheat P.I. 178 383 

 which is a very important parent in stripe rust resistance breeding in 

 the U.S.A. (Sharp and Hehn, 1967), and the "supporting differential" 

 Reichersberg 42 which gave a clearer reaction than usual. The differen- 

 tiation of race 20A is shown in Table 3. 



Table 3. Differentiation of Race 20A of stripe rust into 



3 races by use of seedling reaction of supporting differentials 









Rac 



e 20A 





Varieties 



Variation 1 



Variation 2 



Variation 3 



Heines Kolben 



IV 





II- 



0+ 



Reichersberg 42 









IV 







P. I. 178 383 



i-0 





i-0 



IV 



Lee 



IV 





IV 



IV 



Race 20A is characterized by virulence for the differential Lee and 

 some virulence for the differential Heines Kolben. 



FIELD RACES 



Now it is time to switch over to the field races, described by 

 Zadoks (1961, 1963) and Ubels, Stubbs and s'Jacob (1965). Plants in the 

 seedling stage very often are more highly susceptible than in later 

 stages of development, and the adult plant is able to show more differen- 

 tiation of rust infection (type and degree) than the young one. Based on 

 field infection data from all over Europe, Zadoks concluded that field 

 races could be defined. Ubels, Stubbs, and s'Jacob (1965) provided the 

 following interpretation of their results. Flamingo race and Peko race, 

 both defined as race 54 in the greenhouse, have a distinct difference in 

 the field race trials. Leda race and Heine VII race, both in the race 8 

 group, show differences on Leda. Somewhat exciting was the Cleo race, 

 which infected Heine VII and some other varieties in the field, and gave 

 the race 3/55 picture in the greenhouse tests . 



Concerning the varieties themselves, each seems to have its own race 

 infecting it to a higher degree than the other races would. 



So, in certain cases, field observations and experiments in isolated 

 field plots split up the race determination done in the greenhouse. We 



