BLISTER RUST RESISTANCE OF WHITE PINES IN EUROPE 237 



Figure 3 shows the infection results of the cross P. strobus x P. 

 peuae; many of these offspring survived. The infection level is high, 

 nearly as high as on the P. strobus offspring, but the plants were seldom 

 killed. Figure 4 shows an offspring from open pollination of a cross 

 (P. strobus x P. peuae) . The course of the attack is very similar to that 

 seen in Fig. 5. 



In 1958, Denmark foresters harvested seed from selected trees in the 

 natural range in Yugoslavia. No infections have been recorded in the 

 progenies. In England, 1 of 22 individuals was infected in a test (British 

 Forestry Commission, 1960) . In Germany, P. peuae has not been infected 

 in the Botanical Garden in Hann. Mtlnden, in the arboretum at H^rsholm, 

 nor in the Forest Botanical Garden since 1876. 



INTRODUCED WHITE PINES FROM ASIA 



FIN US ARMANDII F RANCH. 



This species is native to western and southwestern China, south- 

 eastern Tibet, northern Burma, and northeastern India, and to the islands 

 of Hainan and Taiwan. The first generation in Denmark was not attacked 

 by C. ribiaola. P. armandii was introduced into Denmark in 1926; seed 

 was collected by Joseph F. Rock, October 1925, in central Kansu. After 

 open pollination (1957), offspring from the first generation, exposed to 

 natural infection, did not show any attack by C. ribiaola although there 

 was high infection of P. strobus seedlings in the same area. 



PINUS GEIFFITHII 



This species is native to the Himalaya Mountains, West Pakistan, 

 northern Burma, and Yunnan province, China. It is supposed to be resistant 

 to C. ribiaola. Meyer (1954) mentions a hybrid (P. strobus x P. griffithii) 

 that was not infected by the fungus. Schenck (1939) refers to an attack 

 on the species in Oldenburg, Germany. The Report on Forest Research 

 (British Forestry Commission, 1961) mentions that P. griffithii again was 

 noticeably resistant and P. holfordiana A.B. Jacks. (P. griffithii x P. 

 ayaaahuite Ehrenb.) was susceptible. Boyce (1926) mentioned findings near 

 Oxford, England, where P. strobus was heavily infected and P. griffithii 

 was not. In the Arboretum at H0rsholm a hybrid between P. ariffithii and 

 P. strobus was infected, whereas the pure P. griffithii was healthy. The 

 rust was also recorded in Belgium, Sweden, and Switzerland (Spaudling, 

 1929). 



PINUS KORAIENSIS SIEB. & ZUCC. 



This species is native to Korea, eastern Manchuria, southeastern 

 Siberia, and Japan. Schenck (1939) states that P. koraiensis is not 

 attacked by C. ribiaola in the U.S.A., and that P. koraiensis in Germany 

 situated near a highly infected stand of P. strobus was not attacked. 



Pinus koraiensis in Denmark, grown in the Forest Botanical Garden 

 since 1890, has not been attacked by C. ribiaola, and the same is the 

 case with several offspring from these trees. 



