COMPUTERIZED MAPPING OF BLISTER RUST EPIDEMICS 

 IX NURSERY SEED BEDS 



Roger A. McCluskey 

 Intermx>untain Forest and Range Experiment Station, 

 Forest Service, U. S. Department of Agriculture, 



Moscow, Idaho, U.S.A. 



ABSTRACT 



As part of a long-range U.S.D.A. Forest Service program for 

 development of varieties of Einus monticola resistant to 

 Cronartium ribicola, 2-year-old seedling progenies were 

 artificially inoculated in nursery seed beds. Success of 

 inoculation varied, especially across long seed beds or 

 several seed beds that had been inoculated simultaneously. 

 Because of the variation, rejection of lightly or non- 

 inoculated portions of seed beds was essential to the 

 validity of analyses. Because of this problem and the large 

 body of test data involved, a FORTRAN' IV computer program 

 was designed to process data and produce maps showing 

 blister rust needle-lesion frequency on individual seedlings 

 within nursery beds. 



In the fall of 1964, seeds were planted in an Intermountain Forest 

 and Range Experiment Station nursery at Moscow, Idaho, to test more than 

 100 parents for transmission and heritability of blister rust resistance 

 in western white pine. The seeds were sown in 5,790 rows and all seed 

 spots (16 per row) identified. This planting produced 61,000 seedlings. 



All seedlings were artificially inoculated with Cronartium ribicola 

 at age 2. About 10-12 months later, all were examined for needle-lesion 

 frequency. Success of inoculation varied; especially across long seed 

 beds or across several seed beds that had been inoculated simultaneously. 

 To detect inoculation "cold spots" a computer program was written that 

 would produce maps of the seed beds showing the intensity class of needle- 

 lesion frequency for each seedling. Mapping enabled us to delete from 

 farther analysis data from lightly or noninoculated portions of seed 

 beds . 



A 13-row portion of a seedling bed is shown on the sample map (Fig. 1) 

 Row number and parent identification are to the left of each row. The 

 seeds were sown in two subrows (eight seed spots per subrow) . Blank 

 spaces in a row indicate that no seedlings are growing in those seed 

 spots; double letters indicate that two seedlings are growing in a seed 

 spot. The area delineated by the broken line contains seedlings with no 

 needle lesions. Since this "cold spot", or noninoculated area, runs 

 across several rows, including a control (9995 x 999), the seedlings 

 within this area were rejected from further analysis. 



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