SPORE VIABILITY AND GERMINATION 



To explore the influence of environmental 

 conditions on spores during dissemination and germi- 

 nation, many experiments were run under controlled 

 and monitored environmental conditions. Experi- 

 ments were made to investigate all spore stages 

 involved in infection of comandra and pine, that is 

 (1) aeciospores on pine, with ability to infect 

 comandra; (2) urediniospores on comandra, with abil- 

 ity to reinfect comandra plants; (3) teliospores in 

 teha on comandra, which form basidiospores; and (4) 

 basidiospores which may infect pines. 



AECIOSPORES 



Annual crops of aeciospores are produced in 

 aecia from perennial mycelium in live bark of cankers 

 of pines. At maturity, aecial peridia rupture and 

 expose dark-orange masses of many thousands of 

 teardrop-shaped aeciospores. These spores are dis- 

 seminated by wind and function as the primary 

 inoculum for infection of comandra. 



Effects of Temperature on Germination 



Mer/20£^. -Aeciospores collected in June from 

 recently ruptured aecia were tested for their ability to 

 germinate at several temperatures. Six samples repre- 

 senting Cache, Targhee, Teton, and Wasatch National 

 Forests were tested. Spores were collected with a 

 small cyclone separator, stored in gelatin capsules, 

 and kept cool until tested within a few days. 

 Collodion membranes floating on distilled water in 

 petri plates were used as the substrate for germi- 

 nation. These membranes were made by pressing large 

 drops of collodion between two glass slides, sepa- 

 rating the slides, air-drying the exposed surfaces, and 

 finally floating the membranes off onto water. Such 

 membranes were uniformly a few microns thick and 

 proved excellent for aeciospore germination. Small 

 masses of spores were blown through a cyclone sepa- 

 rator into a 40-cm.-high settling tower where spores 

 fell onto the test membranes. Germination was simul- 

 taneously tested at 5° C. intervals from 3° to 33° 

 C.±0.5° C. After spores had been incubated 24 hours 

 in darkness, a sodium hypochlorite solution (1 per- 



cent available CI) was atomized onto test surfaces to 

 inhibit further germination. Percent germination was 

 determined by counting at least 200 spores, and 

 length was measured in 20 germ tubes. Counts and 

 lengths were taken using a microscope; fields of view 

 were not chosen systematically, but instead the 

 observer attempted to scatter views over the test sur- 

 face by moving the slide more or less at random. 

 Evaluations of germination of other spore stages pre- 

 sented in this paper were made by this technique 

 unless otherwise indicated. 



Results. -Ahhough germinating aeciospores 

 frequently formed several germ tubes, one tube 

 usually became dominant (fig. 3). When both percent 

 germination and length of dominant germ tubes are 

 considered, temperatures between about 8° and 18° 

 C. are most favorable for vigorous germination, but 

 good germination occurs over a broader range (fig. 4). 

 Only at the extremes of 3° and 28° to 33° C. was 

 germination poor. 



Figure 3.-- Germination of C. comandrae aecio- 

 spore after 24 hours, incubation (X 

 200). Note the distinctive teardrop shape 

 of nearby aeciospores. 



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