New Zealand Journal of Agricultural Research abstracts
Occurrence of the fungal endophyte Neotyphodium coenophialum in leaf
blades of tall fescue and implications for stock health
M. J. CHRISTENSEN
H. S. EASTON
W. R. SIMPSON
B. A. TAPPER
AgResearch Grasslands
Private Bag 11008
Palmerston North, New Zealand
Abstract Leaf blades of tall fescue (Festuca
arundinacea) plants infected with the endophytic fungus Neotyphodium
coenophialum (= Acremonium coenophialum) have often been assumed to
be endophyte-free. However, fungal colonies identified as N.
coenophialum developed following incubation of surface-sterilised leaf
blades from endophyte-infected tall fescues on antibiotic potato dextrose agar.
A standardised fungal isolation technique was developed to assess the
distribution of hyphae within tall fescue leaf blades in three USA-bred
cultivars (`Georgia 5', `Kentucky 31', `Jesup') and a roadside population
(MRSP) from the Manawatu region, New Zealand. Leaf blades of the three USA-bred
cultivars were typically sparsely colonised. In contrast, extensively colonised
leaf blades were present in many MRSP plants, particularly in autumn.
Ergovaline concentrations of up to 3.9 ppm (mean 2.5) were present in leaf
blades of the MRSP grown in a glasshouse. Ergovaline at lower concentrations
(mean 0.4 ppm) was also detected in leaf blades of the tall fescue cultivars
infected with their natural endophytes. These unusually high concentrations of
hyphae and ergovaline observed within leaf blades of the MRSP provide an
explanation of why fescue toxicosis has been especially severe in New Zealand.
Significantly, N. coenophialum from plants of the MRSP was not uniform
in cultural characteristics and conidial length, or in the ability to colonise
leaf blades and produce ergovaline in artificially infected plants of four
diverse tall fescue cultivars. The four inoculated cultivars (`Georgia 5',
`Grasslands Roa', `Kentucky 31', `KFa949') also differed in their interaction
with N. coenophialum from MRSP. The most colonised leaf blades were in
plants from an experimental cultivar of Mediterranean origin (KFa949), and,
surprisingly, ergovaline concentrations were higher in the leaf blades than
sheath. The New Zealand-bred tall fescue cultivar `Grasslands Roa' was also
distinctive in that no hyphae were detected in leaf blades. The concentration
of ergovaline present in pooled leaf blades of `Grasslands Roa' plants was
lower than in those of the other naturally and artificially infected tall
fescue/N. coenophialum populations examined in this study, reflecting
the apparently low concentrations of hyphae present.
Keywords Neotyphodium coenophialum; tall fescue;
Acremonium coenophialum; Festuca arundinacea; ergovaline; fungal
endophytes; alkaloids
New Zealand Journal of Agricultural Research, 1998, Vol. 41: 595-602
0028-8233/98/4104-0595 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (649K); (scanned from paper original: notes about this process)
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