Table 7>. --Number of trees per test, percentage dead due to blister rust, percentage 



resistant seedlings lifted and percentage still living with cankers in 1970 

 in the Elk Creek progeny test plot 









Cankered 



and percent living in 1970 





Test 



year No 



. trees 



Percent Dead 

 rust ly/u 



with old 

 cankers ^ 



with basal 

 cankers^ 



with young 

 cankers 



Percent 

 1 irted 



1952 



2333 



78.5 



1.5 



0.8 



1.2 



18.8 



1953 



740 



83.4 



1.4 



.6 



1.1 



14.2 



1954 



941 



73.4 



4.7 



1.0 



1.2 



20.7 



1955 



1678 



60.5 



8.5 



.8 



16.4 



14.5 



All 

 controls 



405 



94.3 



0.2 



.2 



1.7 



3.7 



^Old cankers are cankers that resulted from infection soon after the trees were 

 outplanted. 



^Basal cankers appear to be cankers that resulted from the initial inoculation when 

 the seedling was 2 years old when in the nursery. 



^Young cankers are those that have shown up recently--3 years prior to the 1970 

 rust inspection. 



^Bingham lifted these seedlings with "high" resistance and moved them to the 

 Moscow Arboretum 1957-1960. 



The last reaction type that we have observed is what is called tolerance. This 

 is a reaction of one seedling that enables it to sustain a great amount of infection 

 without serious growth reduction or mortality. This reaction shows up at very low 

 frequencies . 



The mechanisms of resistance are summarized in table 4, with an indicated 

 epidemiological type and hypothetical genetic control. 



5 



