TAXONOMY, CROSSABILITY AND RESISTANCE OF WHITE PINES 277 



Bingham and staff, 1954-1969 : These new data, presented in the 

 next to last column of Table 2, are based upon artificial inoculations 

 of 2-year-old seedlings of 9 species including: 2 provenances of P. 

 armandii with 63 seedlings; 4 of P. cembra with 32 seedlings; 12 of P. 

 flexilis with 370 seedlings; 5 of P. griffithii with 194 seedlings; 3 

 of P. koraiensis with 39 seedlings; 305 of P. monticola with 30,000+.. 

 seedlings; 2 of P. parviflora with 13 seedlings; 4 of P. pence with 34 

 seedlings; and 6 of P. strobus with 285 seedlings. The strength of this 

 data lies in the fact that most often three or more provenances of a 

 given species were tested. Rankings are based on percentage of seedlings 

 infected, with rank 1 being the least heavily infected, rank 9 the most 

 heavily infected. In all species at least a few seedlings became infected 



The "tentative average rankings" for blister rust resistance (last 

 column, Table 2) are arithmetic averages of the rankings shown for the 

 six observations of the five observers. Questionable rankings received 

 a weight of 1/2. 



CONCLUSIONS 



SPECIES DESERVING IMMEDIATE ATTENTION 



The IUFRO Committee on (resistance to) White Pine Blister Rust 

 selected Pinus griffithii as their first choice for immediate attention 

 (see Committee report, these proceedings) because of the following: 

 its good performance and relatively high level of resistance exhibited in 

 central and southern Europe and the U.S.A.; its extensive range and, 

 thus, probable great genetic variability for resistance, growth, and 

 hardiness. The Committee has also recommended that, as soon as possible, 

 similar attention should be directed toward the moderately resistant P. 

 peuce (also possibly having early-flowering genes, cf. Heimburger, these 

 proceedings) as well as toward the highly resistant but inaccessible 

 southeast Asian species P. armandii and P. koraiensis. The author is in 

 complete agreement with these recommendations, including the suggestion 

 that there should be a revival of white pine species-blister rust resis- 

 tance trails in rust hazard areas of North America, Europe, and Asia. 



OTHER SPECIES DESERVING MORE ATTENTION 



Four other white pines, three of them little-known southeast Asian 

 species related to P. parviflora or P. griffithii (cf. Critchfield and 

 Little, 1966), deserve more attention that they have received in the 

 past. The first of these is P. strobiformis from high elevations in the 

 southwestern U.S.A. and northern Mexico. Certain provenances of this 

 species have good growth potential and have proved to be winter-hardy 

 throughout the U.S.A. (see Steinhoff, these proceedings). Resistance 

 appears to be well above expectation (Table 2), and needs to be confirmed 

 by better and wider testing. Its potential for direct planting, or as 

 a source of resistance, deserves attention in northern European and 

 North American rust hazard areas. The other three almost unknown 

 species deserving more attention are the inaccessible southeast Asian 

 white pines: P. dalatensii , possibly a relative of P. griffithii; P. 

 fenzeliana; and P. wangii of the P. parviflora complex. Although 

 possibly cold-sensitive, slow-growing, and of unknown blister rust resis- 

 tance, these three white pines could become highly valuable sources of 

 resistance. P. wangii and P. fenzeliana grow nearest to any P. armandii- 

 P. griffithii blister rust gene-center. 



