The Interactive Effects of Temperature and Osmotic Potential on the Growth of Aquatic Isolates of Fusarium culmorum.

Resumen

The mycelial growth of 10 Fusarium culmorum strains isolated
from water of the Andarax riverbed in the provinces of Granada
and Almeria in southeastern Spain was tested on potato-dextroseagar
adjusted to different osmotic potentials with either KCl or
NaCl (−1.50 to−144.54 bars) at 10◦C intervals ranging from15◦ to
35◦C. Fungal growth was determined by measuring colony diameter
after 4 d of incubation. Mycelial growth was maximal at 25◦C.
The quantity and capacity of mycelial growth of F. culmorum were
similar at 15 and 25◦C, with maximal growth occurring at −13.79
bars water potential and a lack of growth at 35◦C. The effect of
water potential was independent of salt composition. The general
growth pattern of Fusarium culmorum growth declined at potentials
below −13.79 bars. Fungal growth at 25◦C was always greater
than growth at 15◦C, at all of the water potentials tested. Significant
differences were observed in the response ofmycelia to water potential
and temperature as main and interactive effects. The number
of isolates that showed growth was increasingly inhibited as the
water potential dropped, but some growth was still observable at
−99.56 bars. These findings could indicate that F. culmorum strains
isolated from water have a physiological mechanism that permits
survival in environments with low water potential. Propagules of
Fusarium culmorum are transported long distances by river water,
which could explain the severity of diseases caused by F.culmorum
on cereal plants irrigated with river water and its interaction under
hydric stress ormoderate soil salinity. The observed differences
in growth magnitude and capacity could indicate that the biological
factors governing potential and actual growth are affected by
osmotic potential in different ways.