J. Fargues et al., EFFECT OF TEMPERATURE ON VEGETATIVE GROWTH OF BEAUVERIA-BASSIANA ISOLATES FROM DIFFERENT ORIGINS, Mycologia, 89(3), 1997, pp. 383-392
Effects of temperature on growth on a semisynthetic medium of 65 isola
tes of Beauveria bassiana from different geoclimatic and host origins
were determined. The isolates were grouped according to the climate of
their geographic origin, distinguishing between cool and warm regions
; according to their host origin, distinguishing between isolates from
acridids or from soil associated with acridid populations; and accord
ing to host order. In general, B. bassiana grew at a wide temperature
range from 8 to 35 C. A well defined maximum thermal threshold occurre
d at temperatures of >35-37 C for 50 isolates; >32-35 C for 12; and >3
0-32 C for 1 isolate. The lower temperature threshold for all isolates
tested was below 8 C. Relative growth rate, calculated from the maxim
um growth rate for each isolate, was significantly affected by tempera
ture and isolate. Optimal temperatures were generally between 25 and 2
8 C with several isolates exhibiting optimal growth at temperatures as
low as 20 or as high as 30 C. Relative growth rates were not very use
ful in distinguishing differences among many of the isolates at the ne
ar-optimal temperatures. In contrast, the ability to distinguish diffe
rences in relative growth rates among isolates increased progressively
as temperatures increased above 28 C or decreased below 20 C. There w
ere no apparent relationships between relative growth rates and climat
ic origin. In comparisons of acridid-associated isolates, relative gro
wth rates were higher for the insect isolates at 8 C and for the, Afri
can soil isolates at 35 C. At the other temperatures, no clear relatio
nships were apparent. When comparisons were made according to host ord
er, there were significant differences in relative growth rates accord
ing to host order at 8, 11, 30, and 32 C but not at the other temperat
ures. Since temperature growth responses varied considerably among iso
lates, with some having wide ranges of temperature optima while others
were much more restricted, strain selection according to thermal requ
irements may be warranted when choosing a strain for development as a
microbial control agent.