USDA FOREST SERVICE RESEARCH NOTE NE-105 



1969 



ortheastern Forest 



I ^ 1 

 xperiment Station 



REST SER 



\:et street, upper darby, pa. 



HOW TWO Ti'PES OF FLUCTUATING 

 TEMPERATURE AFFECT THE 

 GROWTH OF FUSARIUM SOLANI 



Abstract. — Growth of six isolates of Fusarium solani on potato 

 dextrose agar was determined with (1) continually changing 

 temperature programs, (2) programs consisting of two alter- 

 nating constant temperatures, and (3) a constant temperature 

 program. All programs had a mean of 70° F, Growth increased 

 with an increase in temperature fluctuation of 10 or 20 "F., but 

 decreased with a fluctuation of 40° F. Significant differences 

 were found in the growth rates of the isolates. 



The change in the growth rate of a fungus with a change from a 

 constant temperature to a fluctuating temperature has been reported by 

 several authors. Smith (4) and Burgess and Griflin (2) used programs 

 that approximated daily temperature changes. Jensen (3) used a program 

 of two constant temperatures, each alternately maintained for 12 hours. 



This study was established to determine if six isolates of Fusarium 

 solani (Mart.) App. &'Wr. emend Synd. & Hans, differ in their response 

 to these two types of fluctuating temperature programs. 



Materials and Methods 



The effect of the two types of temperature programs on the growth 

 of F. solani was determined in an incubator controlled by a cam-type 

 temperature programmer. For each program type, three fluctuating tem- 

 perature regimes, each with a mean of 70° F., were established. The three 

 temperature regimes had fluctuation ranges of 10° (65 to 75° P.), 20° 

 (60 to 80° F.), and 40° F. (50 to 90° F.). The effect of a constant tem- 

 perature regime of 70° F. was also determined. 



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