jimei, I920 Production of Conidia in Giber ella saubinetii 237 



overcrowded, they germinated, forming hypliae which bore masses of 

 conidia within two days as previously described for the sporodochial 

 conidia and ascospores. This conidial production went on indefinitely, 

 if the culture did not dry or become crowded. The ninth generation 

 of conidia from a single ascospore was produced in 20 days by trans- 

 ferring each successive generation to new plates of potato-dextrose agar. 

 These conidia were produced only when the spores were transferred to a 

 favorable medium and kept in a moist, warm atmosphere. When the 

 temperature was lowered or when the culture became dry the conidia 

 did not germinate but remained inert on the surface of the culture. 

 Spores kept in this manner were rather resistant to both desiccation and 

 low temperatures. Germination was obtained after several weeks' stor- 

 age at temperatures of about 3° to 4° C, as well as when stored under 

 dry conditions at room temperature. 



Conidia were produced in two days from mycelium plated from in- 

 fected root and stem tissues as well as from plated conidia and ascospores. 

 Tissues infected with G. saubinetii were surface-sterilized and placed on 

 potato-dextrose agar in poured plates. Conidia appeared on the devel- 

 oping mycelium two days after plating and were present in conspicuous 

 sporodochia-like masses the third day. These conidia were identical 

 with those formed on the mycelium from either ascospores or conidia. 



The conidia formed during the vegetative development were 4 to 5 

 septate (fig. i, B, E) and were of the same shape and size as the sporo- 

 dochial conidia. 



Inoculations on wheat plants showed that these conidia were as viru- 

 lent in producing scab on wheat as were either sporodochial conidia or 

 the vegetative mycelium. The spores germinated and caused infection 

 within the same temperature range as the sporodochial conidia.' 



The work here reported shows that repeated crops of conidia of G. 

 saubinetii can be produced in abundance in short periods of time from 

 ascospores, sporodochial conidia, vegetative conidia, or mycelium, when 

 favorable moisture and temperature conditions obtain. This ability of the 

 wheatscab organism to produce virulent spores in abundance in short 

 periods of time has an important bearing on the development of wheat- 

 scab epidemics. 



