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Forest. 51: 494-495. 



FLOOR DISCUSSION 



(Discussion here also covers the previous paper by Patton.) 



ZUFA: I have a question for Dr. Patton. How fast does the blister 

 rust mycelium grow through the needle? How soon after the inoculation 

 can it reach the stem? 



PATTON: I think Hirt has reported that the minimum time required 

 was about 11-1/2 hours or so. A number of experiments, that were done by 

 Dr. Riker in the early days indicated a minimum time of about 18 hours. 

 So I would say 12 to 18 hours might well be the minimum. This is from 

 the time that teliospores start to germinate, and basidiospores are cast, 

 germinate, and penetrate. I don't know anything at all about the time 

 required for the actual penetration process, but I don't suppose this 

 really takes too long. We have seen vesicles in needles with infection 

 hyphae well down into the mesophyll within '5 days after the inoculation 

 period was started. We gave needles about a 60 or 72 hour inoculation 

 period, and then made our first collection some 5 days after the beginning 

 of inoculation. By that time, the hyphae was well down into the needle; 

 mycelium had started to form, in other words. 



BEGA: I have three questions for Dr. Patton. First, a comment, 

 though. Thank you for reiterating this need for some more basic problem 

 oriented studies on Cronartiwn ribicola, and I hope that you and our 

 friend Leaphart here can keep your groups working in the direction you 

 are. The first question is, have you observed on secondary or tertiary 

 sporidia the percent of vesicle formation either on needles or on 

 cellodian membranes? 



PATTON: We made no counts of that at all. 



BEGA: It's unimportant. I was just curious. The other had to do 

 with needle age in relation to infection. We aged cankers using the 

 Lachmund method for western white pine or Kimmey method for sugar pine, 

 which are both the same, but we count the second-year needles, as infec- 

 tion counts. I think your work is going to throw some light on some of 

 the variables that we have been coming up with relating canker age to 

 climatic years. And then, third, what is the role of the stomata in these 

 older needles that are plugged? 



PATTON: Well, as I said, this is one of these things that we still 

 don't have all the answers to yet. I think that the stomatal plugs play 

 a primary role in the difference in amount of infection we get from the 

 primary and secondary needles. I don't mean to say that primary needles 

 aren't plugged, because they do have plugs, but I think that the number 

 of chances for germ tube entry down as far as the guard cells are much 

 greater in primary needles than in secondary needles. Now, what I'd like 

 to do is follow this thing through. I have the feeling or the impression, 

 and some of our data tend to support the idea, that there is greater 

 plugging as the needle gets older, and perhaps even with some of our 



