TAXONOMY, CROSSABILITY AND RESISTANCE OF WHITE PINES 279 



prefer to have him answer the question then (see Dinus, these proceedings) 



KINLOCH: Can you clarify the basis for the blister rust resistance 

 rankings of white pine species shown in your Table 2? I'm wondering 

 particularly about the relative rankings of sugar pine [Finns lambertiand) 

 and western white pine {Pinus monticold) . Recently I have seen some data 

 from U.S. Forest Service, Region 6, the Dorena Project, indicating that 

 under artificial inoculation sugar pine develops relatively few needle 

 lesions as compared to western white pine. 



BINGHAM: Observations on the relative resistance of the two species 

 here at Moscow are nil. (Notice that the table indicates no comparative 

 observations on sugar pine by Bingham and staff.) And what good infor- 

 mation there is in the table is not based upon needle lesions, but upon 

 bark cankers per million needles, from Bedwell and Childs. I would 

 suggest that Mr. Gerald Barnes of the Dorena Project answer your question. 



BARNES: We completed our first blister rust needle lesion or needle- 

 spot tally on sugar pine and western white pine control-pollinated, intra- 

 species crosses at Dorena (Cottage Grove, Oregon) in the spring of 1969. 

 Dr. Kinloch is right; one of the firmer results of the examination was 

 that the sugar pines on the average had fewer needle spots than the 

 western white pines. The data showed something like 0.4 needle lesions 

 per lineal inch of western white pine needles as compared with 0.1 

 lesions for sugar pine. 



WAN ARSDEL : Have you shown a relationship between the amount of 

 needle spots or flecks and the amount of bark cankers that result, so 

 that you know the relation of spots and cankers is a true one? 



BARNES: No, we have not as yet. 



BINGHAM: Mr. Barnes, I believe your remarks on relative needle 

 spotting of the two pines were based on data from full- or half -sib 

 progenies from phenotypically resistant trees in heavily rusted natural 

 stands. Is that correct? 



BARNES: Yes, but my remarks also extended to the sugar and western 

 white pine control (presumably unselected, non-resistant) seedlings 

 examined in the same tests. The controls gave a similar result — fewer 

 spots on the sugar pine needles. 



BINGHAM: Then, perhaps, Dr. Van Arsdel, the lesser spotting of the 

 sugar pine needles may be a species-wide character. There may simply be 

 a higher level of foliar resistance in sugar pine, but other resistance- 

 genes coming into play later in the development of pine: ruse association 

 may be absent, or less effective. 



MCDONALD: Returning to Dr. Van Arsdel's question on the correlation 

 between needle spotting and canker formation, I have completed a prelimi- 

 nary analysis on this and results indicate one spot per seedling is enough 

 to cause one canker. Thus the correlation of frequency of needle spots 

 with presence or absence of bark cankers breaks down. One needle spot per 

 seedling is as likely to produce a recognizable canker as 100 spots per 

 seedling are. In other words frequency of needle spotting could vary 

 greatly without variation in the probability of cankering on a whole 

 seedling basis. 



