Utilization of VA-mycorrhiza as a factor in integrated plant protection

131

Agriculture, Ecosystems and Environment, 29 Elsevier Science Publishers B.V., Amsterdam Printed in Czechoslovakia

Utilization

of

VA-mycorrhiza

as

a

(1989)

131-135

f a c t o r in i n t e g r a t e d p l a n t p r o t e c t i o n

F. Feldmann ~, N.T.V. Junqueira+, R. L i e b e r e i * Botan. I n s t i t u t ,

Techn. U n i v e r s i t ~ t , P.O. Box 3329, D-3300 Braunschwei8, FRG

+ CNPSD, CP 319, Km 28, Am 010, 59000 Hanaus, Amazonas, B r a z i l

A b s t r a c t : VA-mycorrhiza i n f e c t e d rubber t r e e s r e v e a l an i n c r e a s e in r e s i s t a n c e a g a i n s t a f o l i a r d i s e a s e (South American Leaf Blight) caused by the ascomycete H i c r o c y c l u s u l e i . The l e s i o n s i z e and the production of spores of the pathogen were

significantly

lesions plant

lowered

in

VAN i n o c u l a t e d p l a n t s , whereas the number of

remained unchanged. This s u g g e s t s t h a t the r e s i s t a n c e response of the is

significantly

enhanced phases

resistance of

influenced

by

VAM t r e a t m e n t and demonstrates t h a t

i s not due to i n h i b i t i o n of p e n e t r a t i o n or e a r l y growing

the p a t h o g e n b u t to the m o d i f i c a t i o n of l a t e r e s i s t a n c e responses.

The i n c r e a s e in r e s i s t a n c e by VAN i n o c u l a t i o n i s an important means to c o n t r o l the

epidemiological

measures

are

development

combined

with

of

the

plant

severe

leaf

management,

d i s e a s e . The c o n t r o l breeding

and

use

of

h y p e r p a r a s i t e s in an i n t e g r a t e d c o n t r o l system.

Intr~du~tion: rainforest studies growth

it

The

of

Brazil

was

conditions

artificial

natural in

shown (e.g.

growth which

that St.

area

of

rubber

trees

is

the t r o p i c a l

very poor s o i l s a r e p r e s e n t . In p r e l i m i n a r y

rubber t r e e s form a VA-mycorrhizs under n a t u r a l John,

1980).

Furthermore

i t was proved t h a t

i n o c u l a t i o n o f rubber s e e d l i n g s l e a d s to p o s i t i v e growth responses

in

pot

cultures

interactions rarely

(Feldmann,

has

been

1987).

The

i n f l u e n c e of VAN on p l a n t pathogen

s t u d i e d f o r a number of p l a n t s ( e . g . Dehne, 1982) but

on woody p l a n t s p e c i e s and t h e r e f o r e no c o n c l u s i v e d a t a f o r t r e e s l i k e

Hevea

brasiliensis

a r e a v a i l a b l e . YounS Hevea t r e e s r e v e a l a r y t h m i c a l srowth

p a t t e r n , in which l e a f f l u s h i n S occurs. Leaves a r e produced e v e r y 6 t o 8 weeks and

need

misses

about

(k

to

4 weeks f o r m a t u r a t i o n . Within t h i s phase f o u r developmental D)

can be d i s t i n g u i s h e d by morphological c h a r a c t e r i s t i c s .

The

l e a v e s a r e showins an e x p r e s s e d l e a f age r e s i s t a n c e to f u n s a l a t t a c k . Stages A and

B a r e g e n e r a l l y s u s c e p t i b l e to a h i s h number of f u n s a l p a t h o s e n s , s t a s e C

i s of i n t e r m e d i a t e r e s i s t a n c e and s t a s e D i s not i n f e c t i b l e by b i o t r o p h i c l e a f pathogens.

In

indigenous

VAM p o p u l a t i o n s ,

behaviour

t h i s study t h e i n f l u e n c e o f VAN i n o c u l a t i o n , a d d i t i o n a l to the

against

plant

growth,

Microcyclus

l e a f development end r e s i s t a n c e

ule__~i,

the

causal

asent

of

the

South American Leaf B l i s h t , was e v a l u a t e d . Material clones with

and Fx

P l a n t s of the age of 14 months of t h e d i f f e r e n t Hevea

3925, Px 4098 and IAN 6158 ( p r o p a s a t e d by buddins) were i n o c u l a t e d

Glomu~

Hannover,

methods:

etunicstum

(mixtures

of

Isolates

D 13 and T 6 of Dr. Dehne,

bound t o expanded c l a y in u n s t e r i l i z e d

s o i l ) . The p l a n t s were grown

under f i e l d c o n d i t i o n s i n Hanaus, Amazonas, Braztl~ in black 1 5 - 1 - p o l y e t h y l e n e bass. 150

A f t e r an i n c u b a t i o n t l ~ e of f i v e months the l e a v e s were i n o c u l a t e d with 000

epores/ml of H t c r o c y c l u s u l e i usin 8 a spray pump. The l e a v e s were a t

the s u s c e p t i b l e developmental s t a s e B (6 days a f t e r bud b , J r s t ) . The e v a l u a t i o n of

the

scale of

l e s i o n t y p e s was c a r r i e d out 10 days a f t e r i n f e c t i o n a c c o r d i n 8 t o the of

five

Junqueira, 1986. The l e a f growth p a t t e r n was observed over a period months

(Junqueira, Results.

1.

resiatering

every day the developmental s t a g e of the l e a v e s

1986). Leaf

developmental

pattern:

the growth p ~ t t e r n of mycorrhizal

133

p l a n t s did not show changes in the time course of the development. Neither the time

needed

for

flushing

or l e a f maturation was modified nor t h e number of

l e a f f l u s h e s produced during the o b s e r v a t i o n period o f S months. The number of leaves

per

flush

and l e a v e s per plant was not s i g n i f i c a n t l y modified in VAN

t r e a t e d p l a n t s . The macroscopic growth p a t t e r n of a l l t e s t e d ~lones was within the normal d e v i a t i o n seen in the c o n t r o l s . 2.

Development

influenced

in

of

the

d i s e a s e : the development of the d i s e a s e was markedly

VAN i n o c u l a t e d p l a n t s , a) P l a n t s of the ~lone Fx 3925 without

VAN i n o c u l a t i o n

( c o n t r o l s ) revealed e x c l u s i v e l y spore producing l e a f l e s i o n s

after

with

infection

inoculated the

plants

more

leaf

sporulating

as

N.

ulei

whereas

in the G. etunicatum

64 Z of a l l l e s i o n s produced the pathogen spores. In

(controls) lesions

was

whereas strongly

in

the

VAN t r e a t e d p l a n t s the number of

reduced

t o 1 1 Z . In the h i g h l y r e s i s t a n t

IAN 6158 no spore p r o d u c t i o n of the pathogen was seen in c o n t r o l p l a n t s

well

as

correlated producing plants

only

pathogen

r e s i s t a n t c l o n e Fx 4098 the pathogen produced spores in 48 Z of a l l

lesions

clone

the

in with

areas

of

clone

VAN t r e a t e d

plants,

b) A r e d u c t i o n of the l e s i o n s i z e was

the

of. the

plant

in

ability clone

Fx

Fx

to

reduce the number of spore

3925 but not in the clone Fx 4098. In c o n t r o l

3925 t y p i c a l l y l a r g e l e s i o n ~ of more than 1 mm~ were

produced (72 Z) whereas in VAN t r e a t e d p l a n t s only 2 1 Z of the l e s i o n s were of that

large

modification eignifi~ant. in

size. of

In the

clone non

IAN 6158 no s p o r u l s t i n g l e s i o n s occured but the

sporulating

lesions

in

VAN t r e a t e d

p l a n t s was

In the c o n t r o l p l a n t s a l l l e s i o n s were n e c r o t i c and 0 . 5 t o 2.0mm

diameter. In VAN i n o c u l a t e d p l a n t s about 54 Z of a U l e s i o n s were t i n y and

chlorotic,

c) The number of l e s i o n s produced per l e a f area was not influenced

s i g n i f i c a n t l y by VAN t r e a t m e n t of the p l a n t s but was dependent on the inoculum d e n s i t y of the pathogen.

134 Discussion:

Rubber t r e e s provide two d i f f e r e n t ezperi m en~al m at eri al s for the

study of VAt4-influences on plants. These are seed-Brown pl ant s udth very youn8 r o o ts

without a well expressed t aproot , which are i nfect ed by VA funBl within

7

9 weeks a f t e r sowin8 (Feldmann. 1987). and plants with a well developed

to

root

system c o n s i s t i n s

are inoculated with

in a c e n t r a l t aproot and l a t e r a l r o o t s (these plants

8enet~celly

identical

plant

material

durlns

breedins

procedures and are the "budded stumps" used to build up new p l a n t a t i o n s ) . VAN-inoculated an

Increased

s e e dl i ns s behave l i k e other VAN-inoculated pl ant s. They reveal production of biomass (Feldmann. 1987; Zambolim. 1988). When 14

months old budded stumps are inoculated with VAN they do not show any increase in

above

8round

btomass production within half a year a f t e r inoculation but

they reveal s d i s t i n c t modification of t h e i r reactions aaatnst l e a f pathoBens. Resistance

reactions

knowledae of 8enetically

the

er e

lesion

defined,

normally

difficult

to evaluate. But the d e t a i l e d

types described by Junqueira (1986) and the use of

veaetattvely

propaaated

material provided us with the

p o s s i b i l i t y to analyse f i n e 8radusted d i f f e r e n c e s in r e s i s t a n c e responses. The data

presented

here

unequivocally

shoe

that

the

VAN-association

causes

physioloaical chanaes relevant to the r e s i s t a n c e react i ons in the leaves, even when no macroscopic modification of the plant can be seen. The enhancement of the r e s i s t a n c e of the plant alon8 with the reduction of the patho8ens

spore

production,

epidemloloaically rubber destaned of

plantations

here

caused

by a VAN-funaus, i s an important

f a c t o r f or the c o n t r o l of the South American Leaf Bllsht in of

Brazil.

The cowbination

of

VAN-inoculum with well

plant manaaement measures, crown buddina, Nixed croppln B and the use

hyperparssites can lead to a complex system of i n t e a r a t e d plant p r o t e c t i o n

in b r a z i l i a n rubber cul~ivation.

AcknowledRements: ~ r t s

of these studies were flnanc~lly supported by the DAAD

(FRG) and CAPES (Brazil).

135

References: Dehne, H.-W.: Interaction between VkH-fungi and plant pathogens; Phytopathology 72(8), 1982, pp. 1115-1119, Feldmann, F.: Horphologische und phystologtsche Ver~nderungen in Hevea-Wurzeln im Zuge der

Bestedelun8 durch bodenbUrtlge Pilze; Diplom-Thesis, Technische

Universittt Braunschwelg, 1987. Junquetra,

N.T.V.; Chaves, G.H.; Zambolim, L.; Gasparotto, L.; Alfenas, A,C.:

Vartabilidade fisio168ica de Mictocyclus ulei; Fitopatologta Brastleira 11(4), 1986, pp. 823-833. St.

John,

T.:

Uma l i s t s

de esp6cies

de

plantas

tropicals brastletras

naturalmente tnfectadas com micorriza vesicular-arbusculsr; Acta Aaazontca lO(1)s 1980, pp. 2~9-2~,

Zambolim, L.: pers.comm.; Universidade Federal de Vi¢osa, MG, Brazil~ 1988.

Feldmann, F.w J u n q u e i r a , N.T.V. and L i e b e r e i e R., 1989: Utilization of vesicular-arbuscular mycorrhiza as a factor

in integrated plant protection. 29:

131-135.

Agric. Ecosystems Environ.,