INOCULATION OF EASTERN WHITE PINE WITH BLISTER RUST 379 



The use of fresh inoculum is undoubtedly preferred over stored 

 inoculum, but if large quantities of inoculum could be stored conveniently 

 under conditions that would favor high viability of the teliospores or 

 basidiospores, progeny testing might be greatly facilitated. 



Although trials have not been extensive, efforts to store telia for 

 extended periods have not been very successful. Early studies, such as 

 those by Spaulding and Rathbun-Gravatt (1925, 1926), were directed 

 mainly to determining longevity of teliospores or basidiospores in nature. 

 Storage of picked leaves packed in shallow layers between newspapers at 

 about 4°C has been successful for up to a week or so, but we have little 

 information on how long such storage would be successful. If leaves are 

 stored moist, contaminating fungi soon cause deterioration of the leaves 

 and the rust; drying of the leaves and telia, however, can also affect 

 teliospore viability. More remains to be learned about such methods of 

 handling telia-bearing ribes leaves. 



The report of successful storage in liquid nitrogen of the telia of 

 Cronartium fusi forme Hedge, and Hunt by Kinloch (1964) and the experience 

 of Loegering, Harmon, and Clark (1966) with liquid nitrogen storage of 

 urediospores of Puccinia graminis tritici Erikss . 8, E. Henn . gave promise 

 that below-freezing storage of telia might be satisfactory. Boyer (1962) 

 found that urediospores, telial columns, and basidiospores all maintained 

 viability for only very short periods when stored frozen at -10°C, alone 

 or over calcium chloride. In a series of trials at Wisconsin (Patton 

 and Johnson) 2 detached telia and telia-bearing ribes leaves were stored 

 under liquid nitrogen with absolutely no success, regardless of prestorage 

 or poststorage treatments. 



Greenhouse production of inoculum 



Maintaining inoculum in the greenhouse or growth room in smaller 

 quantities for specific experimental purposes also has its hazards, and 

 although these are rarely mentioned in the literature, they are likely 

 to be faced in resistance studies. The extreme susceptibility of ribes 

 to mites requires that close attention be given to preventive and thera- 

 peutic sprays with miticides. Changing susceptibility of the leaves and 

 different temperature requirements for production of uredia and telia 

 must be constantly considered. Production of uredia and telia on detached 

 leaves floating on nutrient solutions has been tried, but so far has not 

 proved successful (Boyer, 1962) . 



INFLUENCING FACTORS 



The Components of Inoculation 



The emphasis in most inoculation methods is on placing the inoculum 

 at an infection court and providing conditions favorable for reactiva- 

 tion of that inoculum. But since the purpose of inoculation is to obtain 

 infection, further consideration must be given to the fact that each 

 stage of development requires different environmental conditions 

 (Ellingboe, 1968). Germination is but the first step in a series that 

 must occur before infection results, and the events in this series are 

 modified by internal and external factors related to the spore, the host, 



Unpublished data, University of Wisconsin Department of Plant 

 Patho logy . 



