320 ALLAN KLINGSTROM 



Tests have also been made to determine the significance of the con- 

 centration of spores in the water-suspension inoculum, but these have not 

 led to conclusive results. It is difficult to make a homogenous suspen- 

 sion of aeciospores in water. Two drops of Tween 80 per liter water 

 make the suspension more stable and do not influence spore germination 

 in laboratory or field tests. In the experiments described above, the 

 number of spores in the inoculum has been about 10,000 per droplet. Tests 

 with mixtures of spores from different collections have also been 

 inconclusive. 



SUMMARY 



M. pinitorqua has a wide range in the whole of Europe and in adjacent 

 parts of Northern Asia. It is a part of an extensive Melampsora leaf 

 rust complex. 



Dry aspen leaves with M. pinitorqua teliospores can be kept for a 

 long time at low temperatures as inoculum. The germination ability of 

 the teliospores increases during the spring, which makes it necessary 

 always to check the germination ability of inoculum. 



Germinating teliospores and basidiospores are very sensitive to dry 

 conditions and higher temperatures. Successful inoculation experiments 

 have been carried out both in greenhouse and nursery, but as yet no 

 systematic pine resistance tests are being carried out. 



P. pini is a very common pine-to-pine rust in northwestern Europe; 

 its range in Europe and northern Asia has not yet been fully established. 



Most reports on successful inoculations suggest that infection can 

 be made only on the annual shoot and that wounds are necessary. 



Current research on an inoculation method with aeciospores suspended 

 in water is described. Even year-old plants can be inoculated as well 

 as older pines. And pines are susceptible during a considerable time in 

 the early summer. The inoculation experiments are influenced by resis- 

 tance factors, and one obstacle has been to find pine material of a 

 suitable susceptibility. 



LITERATURE CITED 



Bolland, G. 1957. Resistenzuntersuchungen Uber Kienzopf und SchUtte an 



der Kiefer. Der ZUchter 27: 38-47. 

 Gaumann, E. 1959. Beitrage zur Kryptogamenflora der Schweiz. Die 



Rostpilze Mitteleuropas. Vol. 12. BUchler 5 Co . , Bern. 1407 p. 

 Haack, F. 1914. Der Kienzopf (Peridermium pini (Willd.) Kleb.). Seine 



Ubertragbarkeit von Kiefer zu Kiefer ohne Zwischenwirt . Zeitschrift 



ftlr Forst- und Jagdwesen 46: 3-46. 

 Hiratsuka, Y. 1969. Endocronartium, a new genus for autoecious pine 



stem rusts. Can. J. Bot. 47: 1493-1495. 

 Klebahn, H. 1938. Offene Fragen und neue Beobachtungen ttber die 



rindenbewohnenden Blasenroste der Kiefern nebst Bemerkungen Uber 



einige andere Rostpilze. Zeitschrift ftlr Pflanzenkrankh. 48: 369-410. 

 KlingstrOm, A. 1963a. Melampsora pinitorqua (Braun) Rostr. - Pine 



twisting rust. Stud. Forest. Suec. 6: 1-23. 



