Relationships between nutrient content and antioxidant capacity

in Lolium perenne plants associated with Epichloë endophytes Milton Carlos Soto-Barajas, Elena Mellado-Ortega, Iñigo Zabalgogeazcoa,

Juan B. Arellano, Beatriz R Vázquez de Aldana, Institute of Natural Resources and Agrobiology of Salamanca, IRNASA-CSIC, SPAIN

Perennial ryegrass (Lolium perenne) is one of the most important forage and turf grasses in the world. This grass is often infected by Epichloë endophytes and in natural populations phenotypic and genotypic diversity is found among fungal isolates. Although Epichloë endophytes are only present in aerial parts, they can alter belowground components and processes of the grass host.

To determine the effect of Epichloë endophytes on nutrient and antioxidant capacity of Lolium perenne plants, in a very diverse set of plants obtained from natural populations. To know whether the antioxidant capacity is related to nutrient content of L. perenne.

Objective

L. perenne plants:

Epichloë-infected (E+)

non-infected (E-)

M1

M2

M3

Stroma

Transplant to experimental

field

Harvest at flowering stage: - Biomass production - Mineral content (ICP method) - Total antioxidant capacity

(TEAC), by FRAP method

Results and discussion

This research was financed with project AGL2011-22783 from Spainsh Ministry of Economy and Competitiveness

A heterogeneous set of Lolium perenne plants was collected at six locations in Western Spain.

Materials and Methods

Three different morphotypes of Epichloë endophytes ocurred in E+ plants

M2S

E+ E- Significance DM (g/plant) 35 56 0.442

Tiller number 68 101 0.321

N (g/kg) 13.46 13.45 0.958 P (g/kg) 2.70 2.99 <0.001 K (g/kg) 10.37 10.39 0.937 Ca (g/kg) 2.34 2.51 0.048 Mg (g/kg) 1.06 1.05 0.952 S (g/kg) 1.62 1.83 0.005 Na (g/kg) 0.405 0.476 0.132 Mn (mg/kg) 30.88 27.86 0.049 Zn (mg/kg) 18.47 18.55 0.645 Cu (mg/kg) 4.65 4.58 0.67 Mo (mg/kg) 1.01 1.16 0.094 Co (mg/kg) 0.043 0.041 0.975 TEAC (mmoles

trolox/100 g plant) 3.659 3.897 0.309

r=0.342 P=0.002

r=0.395 P<0.0001

r=0.402 P<0.0001

r=0.439 P<0.0001

r=0.307 P=0.007

r=0.398 P<0.0001

r=0.510 P<0.0001

Plant growth parameters (dry matter production (DM) and tiller number); mineral content and total antioxidant capacity (TEAC) of Lolium perenne plants as affected by endophyte status Plants infected with asymptomatic endophytes (M1, M2 and M3) did not differ in their concentration of minerals and TEAC. Plants with choke disease (MS2) had greater nutrient content and TEAC than asymptomatic E+ plants.

Distribution of variables in the factorial plane delimited by the components I and II, which accounted for 55% of the total variance. Plant growth parameters are on the negative part of the component I, and minerals and TEAC on the positive part .

Ordination of plant samples on the factorial plane delimited by components I and II. There is not a clear differentiation between infected (E+) and non-infected (E-). Plants with choke disease caused by Epichloë typhina (M2Ch) are located in the positive part of the component I and related to high mineral content and TEAC values.

The antioxidant capacity (TEAC) was correlated with the concentration of several mineral elements in L. perenne This relationship was idependent of Epichloë endophyte. Some of these metals, such as Ca and Mn play a key role as signals or enzyme cofactors in defense responses against oxidative stress. The enhancement of the superoxide dismutase activity in plants with choke disease will be measured in a future study. In any case, these relationships suggest that Epichloë endophytes not only alter nutrient balance but also the antioxidative capacity of L. perenne revealing significant metabolic changes in plants.

-1.000

-.500

.000

.500

1.000

-1.000 -.500 .000 .500 1.000

Com

ponent

II

Component I

DM

Tiller

Na

S

P Ca

Mg Zn

Mo

TEAC Co

Cu

Mn

K N

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

E- E+ M1 M2 M3 M2S

Infection . Morphotype

Ca (

g/k

g)

Calcium

a b

a

a

a

b

0

10

20

30

40

50

60

E- E+ M1 M2 M3 M2S

Infection . Morphotype

Mn (

mg/k

g)

Manganese

a b a

a

a

b

0.0

0.5

1.0

1.5

2.0

2.5

3.0

E- E+ M1 M2 M3 M2S

Infection . Morphotype

S (

g/k

g)

Sulfur

a b a

a a

b

0.0

1.0

2.0

3.0

4.0

5.0

E- E+ M1 M2 M3 M2S

Infection . Morphotype

TEA

C (

mm

ol/

100g p

lant)

Antioxidant capacity

a a a

a

a

b

Multivariate analysis: PCA

E+ = endophyte-infected E- = non-infected