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Summer Dormancy and Endophyte Infection in Tall Fescue
J.L. Underwood1, C.P. West1, D.P. Malinowski2, C.A. Guerber1, and B.C. Grigg1
1University of Arkansas2Texas AgriLife Research
Continuation of climatic change creates challenges for cool-season perennial grasses
Need for summer-dormant cool-season grasses in drought-prone transitional zones
Mediterranean-origin perennial grasses offers possibilities
Little is known about the role of endophyte in summer-dormant tall fescue
Justification
(West, 1998)
Endophyte generally necessary for persistence south of this line Summer-dormant fescue
Cool-season grasses in drought-prone transitional zones
Summer active
Incompletely dormant
Completely dormant
Ability to survive summer stresses by ceasing growth & senescing vegetative tissues despite occasional summer rains (Volaire & Norton, 2006)
Determine influence of endophyte presence on expression of summer dormancy and survival in tall fescue
Objective
HypothesisSummer drought survival in summer-dormant fescues is more highly controlled by plant genotype than by endophyte presence.
Materials and MethodsLocations: Fayetteville, AR and Vernon, TX
Summer-dormant tall fescue:Flecha (E-)Flecha MaxQ (E+)TX06V-BEF (E-)TX08V-BEI (E+)
Summer-active tall fescueKentucky-31 (E-)Kentucky-31 (E+)
Irrigated and Non-irrigated
Materials and Methods
Biomass yields
Materials and Methods
Biomass yieldsTiller-base water content
Materials and Methods
Biomass yieldsTiller-base water contentShoot senescence
Materials and Methods
Biomass yieldsTiller-base water contentShoot senescencePlant survival
4 Jan 4 Feb 5 Mar 1 May 3 Jun 1 Jul 5 Aug 8 Sep 2 Oct 1 Nov 4 Dec
kg D
M h
a-1
0
1000
2000
3000
kg D
M h
a-1
0
1000
2000
3000
KY FL TX
(a) Nonirrigated
(b) Irrigated
2008
2008 KY FL TX
b
a aba
b caab
a
b
b a
b
b
aab
abb a
ba
a
a
b
a
c
b
ab b
a
bc a
ab
ab
c
Fayetteville Biomass
Vernon Biomass
4 Feb 7 Mar 8 Apr 5 May 3 Jun 3 Jul 3 Aug 2 Sep 1 Oct 1 Nov 1 Dec
kg D
M h
a-1
0
1000
2000
3000
KY FL TX
kg D
M h
a-1
0
1000
2000
3000
KY FL TX
(b) Irrigated 2008
(a) Nonirrigated 2008
a
b
c
a
b
c
a
b
b
a
b
b
a
bc
a
a
b
a
bc
aa
b
a
ba
b
b
a
b
c
a
a
b
a
a
b
aa
b
a
b
c
a
a
b
a
ab
aa
b
b
a
b
c
Fayetteville 2007g
H2O
g-1
DW
0
2
4
6
8
KY FL TX
Tiller-base water content
a
b
b
aab
abb
abb
31 May 2 Jul 31 Jul 23 Aug 27 Sep
% S
enes
cenc
e
0
10
20
30
40
50
60
KY FL TX
Senescence
a
babb
aa
b
a
b
a
aa a
b
Survival 2008Water
treatment
Endophyte Fayetteville, AR Vernon, TX
Population status 3 June 1 July 1 Nov 3 June 3 July 1 Nov ---------------------------% Survival----------------------------
Non- KY E+ 88 88 85 74 74 36Irrigated E- 77 74 74 75 74 38
FL E+ 99 99 99 98 98 94E- 99 99 99 97 97 97
TX E+ 100 100 100 98 99 98E- 100 100 100 99 99 99
Irrigated KY E+ 98 97 96 47 49 30E- 97 96 99 73 71 44
FL E+ 99 99 99 93 95 92E- 100 100 99 95 95 91
TX E+ 100 100 99 99 97 97 E- 99 100 100 99 99 94
SummarySummer-dormant tall fescue populations reduced their growth earlier and exhibited lower monthly biomass yields, tiller-base water content, and greater senescence and survival than summer-active tall fescue.
The semiarid environment of Vernon allowed for the differences in degree of dormancy among cultivars to be seen more clearly than in the humid environment at Fayetteville.
QuestionsDoes the endophyte affect the expression of summer dormancy?
No, it is under plant genotypic control.
Does the endophyte promote persistence in summer-dormant tall fescue?
No benefit from endophyte infection was found in summer-dormant tall fescue.
Is summer dormancy a useful strategy for ensuring summer survival in a humid environment?
Although persistence was not a problem, there was limited winter growth.
QUESTIONS ?
