Botli initial aeciospore cultures and their derived urediospore cultures yielded a high 

 proportion of cultures producing teliospores when grown in a cool temperature, but a most 

 important difference showed up when culture ages were compared (table 10) . Few aeciospore 

 cultures produced teliospores in less than 28 days, whereas nearly all the genetically related 

 urediospore subcultures had produced their teliospores by 28 days. 



We conducted our first test of temperature effects on urediospore subcultures (1/single 

 aeciospore culture) for another population of aeciospore cultures isolated in 1976. When we 

 compared the 1976 and 1979 subcultures, a highly significant difference existed between the 

 two populations (table 11), but both populations tended toward the early production pattern. 



The 1976 and 1979 aeciospore cultures were also compared because we had no previous data 

 on aeciospore cultures grown in both warm and cool chambers. The result was consistent (table 

 12) in that the aeciospore cultures in the cool chamber produced telia before those in tlie 

 warm cliamber. Also, both were consistent in not producing teliospores at an early age. 



Finally, most urediospore subcultures within a single aeciospore line showed little 

 variation in age at teliospore appearance, and 2 (C-9 and C-70) of the 18 lines that had 

 complete sets of 5 subcultures failed to produce any teliospores by 49 days (table 13). 



Table 10.--Wumiier of single aeciospore cultures and urediospore subcultures of 

 Cronartium ribicola that produced teliospores at various times after 

 inoculation when grown on Ribes hudsonianum_ var. petiolare clone INT-1 

 at 55°F+2 (13°C+1) 





Days 



after 



inoculation 





Inoculation spore type 



21 



28 



35 



49 



Total 



Aeciospores 







2 



11 



45 



58 



Urediospores 



19 



18 







4 



41 



Total 



19 



20 



11 



49 



99 



= 76.52 P of larger " 0.0005 



d.f. - 3 



Table 1\ . --Number of Cronartium ribicola urediospore subcultures from two populations 

 of single aeciospore cultures that produced teliospores at various times 

 after inoculation when growing at 55 F+2 (13 C+1) (16 hr days) on 

 Ribes hudsonianum var. petiolare INT Clone- 1 



Days after inoculation 



Subculture source 





21 



28 



35 



Total 



1976 Single aeciospore 



culture 



39 



83 



49 



171 



1979 Single aeciospore 



culture 



19 



18 







37 



Total 





58 



101 



49 



208 



= 19.49 P of larger x^ = 0.0005 



d.f. = 2 



7 



