416 ALLAN KLINGSTROM 



frequently disturbed by resistance factors, attempts to discover other 

 types of differences between the races are of great interest. In this 

 connection primary attention is directed to Hiratsuka's work (1968), con- 

 cerning morphology and cytology of aeciospores and germ tubes. He 

 describes the host alternating race as binucleate with dichotomous germ 

 tubes which lack septa. The aeciospores of the pine-to-pine race are 

 described as uninucleate to some extent (16 to 28%) and with septa in the 

 germ tubes. This information could be used as a complement to inocula- 

 tion tests. 



As far as the pine-to-pine race is concerned, the normal distribu- 

 tion biology has not been clarified. During my own field tests I have 

 sometimes noticed that the aecia have been consumed by unidentified 

 insects. The idea that insects might play a part as vectors is not a new 

 one, but that they should be directly responsible for consuming the 

 spores has not earlier been reported. Attempts were also made to bring 

 some common Swedish insects- -Hylobius abietis L., Pissodes spp.--into 

 contact with aeciospore-bearing plants. These insects preferred the 

 spore-bearing and enlarged spindleshaped part of the pines. 



These reflections concerning insects led to tests for amino acids. 

 The spores of the two types of rust differ in amino acid content. The 

 analysis is simple where one has access to equipment for high voltage 

 electrophoresis. Amino acids in spores or homogenized pine tissue were 

 extracted in 96% ethanol . The free amino acids in the ethanol were 

 separated at +38°C on paper (Munktell 302, 100 cm x 36 cm), using a 

 formic-acetic acid buffer at pH 2 (25 g and 78 g to 1 Z H 2 0) and an 

 operating potential gradient of SO v per cm for 2 hours. 



Bark tissue that has been attacked by Peridermium contains more 

 amino acids than does corresponding healthy pine tissue. Attention has 

 been directed primarily toward lysine and arginine, but the content of 

 all amino acids is greater in attacked tissue. Spores from the two races 

 of the fungus have also shown differences in the same group of amino acids 

 Peridermium spores have given a distinct reading for lysine and arginine, 

 but this is absent in the samples from the host -alternating Cronartium. 

 Needless to say, this can only be regarded as an indication of the dif- 

 ferences that can exist, and the question must be examined employing 

 more extensive material. 



RESISTANCE BIOLOGY 



Regarding Peridermium , the author has made a large number of cros- 

 sings between infected (Peridermium trees) , infected and healthy (Plus 

 trees), and healthy pines. From this material a few crossings (table 1) 

 have been selected as a complement to my earlier paper on inoculation. 1 

 These illustrate the current values concerning infection of pine progenies 

 from crossings made as outlined above. 



1 See A. Klingstrom elsewhere in these proceedings. 



