3. Incorporate as many horizontal resistance types as possible. 



4. Maintain a fairly low gene frequency for all the vertical resistance 

 types, i.e., 0.3 to 0.4 or less. Two recessive genes with a frequency of 0.5 would 

 result in complete resistance in 42 percent of the progeny as tested in the nursery. 

 Addition of single genes increases resistance rapidly, but since field resistance 

 tends to be even higher than nursery resistance (Steinhoff, 1971; Bingham and others 

 1973), a high gene frequency of any one gene is just not needed. 



SELECTION FOR RESISTANCE 

 Arrangement of Data and Selection Criteria 



The method of rust inspection will permit the ranking of families according to: 

 (1) fewest to highest number of needle spots--type 6, table 4; (2) slowest to fastest 

 stem symptom appearance- -type 7, table 4; (3) lowest to highest level of mortality-- 

 types 11 and 12, table 4. Individuals can be tagged for: (1) percentage of needle 

 infections--type 5, table 4; (2) few needle spots--type 6, table 4; (3) premature 

 shedding of infected needles--type 8, table 4; (4) the reaction type that maintains 

 infected needles but does not develop stem symptoms (short shoot reaction) --type 9, 

 table 4; (5) stem reaction types--type 10, table 4. 



This management of data will permit the selection of the seed orchard trees as 

 follows: 



1. Individual and family selection for reduced frequency of secondary needle 

 spots. 



2. Family selection for slow fungus growth in the secondary needles. 



3. Family selection for slow fungus growth or tolerance in the stem; at the 

 seedling stage it is impossible to separate these mechanisms. 



4. Individual selections for prevention of needle infections, premature shedding 

 of infected needles, short shoot reactions, and -stem reactions. 



Selection Intensity 



The amount of gain that will be made is directly dependent on the proportion of 

 resistant families and individuals saved. Three major points that must be considered 

 are first the number of families available, second the minimum number of families that 

 will be included in a seed orchard, and third the regional planting area for each seed 

 orchard. 



So far, over 3,000 phenotypically resistant white pine have been located within 

 the inland range of western white pine. This is just a small sample of the number 

 available. Several more thousand could be added if necessary to increase the selection 

 intensity. 



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