Endomycorrhiza Infection in Young Faidherbia aZbida:...
Endomycorrhiza Infection in Young Faidherbia aZbida:
Influence on Growth and Development ! : y, i “’ e ’
c COo&. a)0
M. Ducousso~ and J.P. Colonna
Abstract
eflects of inoculation by Glomus mosseae on nodulation andplant growth, and the development
of the endon~ycorrhiral infection were stadied on Faidherbia albida seedlings. The seedlings were
cuftrrred in either polyethylene ba,ps (vol = f L), or 25-L. 50-L, and 75-L PVC (polyvinyl chloride)
tubes containing nonsterilized soils.
Cotnpared with the noninocoiated control, inoculation with Cilomus mosseae enhanced height
(34% increase b bags and 68% in PVC tubes); above-ground hiotnass production (82% and
112%); root hiomass production (44% and 57%): and nodulation (30% and 263%). Endornycor-
rhkal inoculation did not appear to have any impact. either positive or negative, on taproot
elongation.
Ohservatioru revealed that only the apper part of the plant root systenl was infected and that the
inocalunz did not penetrate deeply into the soil. T~US, it is likely that endonlycorrhizal inoculation of
yormg F. albida will prohahly not have a lasring positive impact in tke field.
Introduction
In the first ex
‘ment, we monitored the effects of
seedling inoculati90
n in polyethylene bags (vol = 1 L),
Faidherbia albida, like most of the Acaceae, is capa-
using standard nursery techniques. In the second
ex-
ble of simultaneously forming nitrogen-fixing nod-
periment, seedlings were cultivated in PVC tubes (25
ules and vesicular arbuscular endomycorrhizae
cm in diameter) of various lengths. This experiment
(VAM) on its roots (Ducousso 1990). These infections
represented an intermediate step between the nursery
have been shown to improve seedling development,
conditions (i.e., bags) and Iield conditions by allow-
and have been the focus of studies under controlled
ing observation of root systems and mycorrhizal
de-
conditions in the laboratory and the nursery. Efforts
velopment on plants growing in a larger volume of
to successfully extend these beneficial effects to trans-
soil.
planted seedlings have failed. Outplantings of
Acacia
holosericea, Acacia senegal, and Acacia raddiana in
Senegal demonstrated that beneficial effects of endo-
Materials and Methods
mycorrhizal inoculation diminished after 1 or 2 years.
Interest in F. albida as an element of Sahelian
F. albida seeds (provenance 9012709, DRPF/ISRA,
agroforestry systems (CTFI’ 1988) has stimulated re-
Dakar, Senegal) were pretreated with concentrated
search on mycorrhizal infection on this species in the
sulfuric acid for I h, rinsed well with tap water and
field and its effect on growth. Two experiments were
then germinated for 48 h on moist Sand. After ger-
simultaneously carried out on nonsterilized soi1 rep-
mination, seed coats were removed and the seedlings
resentative of F. albida park zones in Senegal.
were planted in the nursery in either polyethylene
1. Labomtoire de microbiologie forestière. Direction des recherches sur les productions forestières (DRPF). Institut s&égrlnis de recherches
agricoles (ISRA). Ddkdr,Senegal.
2. Laboratoire de biologie et physiologie végétative. ORSTOM, Dakar, Senegdl.
Ducousso, M., and Colonnn, J.P. 1992. Endomycorrhiza infection in young Frri~Wer&~ &Xr: inlluence on growth and development. Pages 151-
156 NI /%r//rcr/~hr ahidr in the West Africnn semi-urid tropics: proceedings of a workshop, 22-26 Apr 1991. Ninmey. Niger (Vandenkldt. R.J.,
ed.). P;wvzheru. A.P. 502 324. Indix Internotionel Crops Research Inrtitute for the Semi-Arid ‘Tropics: and Nairobi. Kenya: Interndtiondl Centre
for Research in Agroforestry.
151
Figure 1. A. Experimental set up showing W C tubes of various lengths 6 weeks after sowing. B. Root
growth in 1.0-m W C tubes 9 weeks after sowing. Five noninoculated plants (right) and five inoculated
plants (left). C. Mycorrhizal infection in S-week-old plants grown in 1-L bags. (Note root coiling.) On the
second plant to the left, taproot branching caused early infection. D. Nodules on roots.
152
bags (vol = 1 L) or in 0.5-m (vol = 25 L), 1.0-m (vol =
root system of each plant. For very young seedlings,
50 L), or 1.5-m (vol = 7.5 L) PVC tubes (25 cm in
samples were taken from Ihe bulked root systems of
diameter) (Fig. 1). All pots were tîlled with sifted
all sampled plants.
Deck soi] (Table 1). Plants were watered daily
In the second experiment, all roots present at the
Woughout thc duration of the experiments.
following depths were observed:
l For 0.5-m PVC tubes: O-10 cm, 20-30 cm, and
40-50 cm.
Tuble 1. Principal physico-chemical characteristics
l For 1.0-m PVC tubes: O-10 cm, 20-30 cm, 45-55
of Deck soi& Bambey, Senegal, 1990.
cm, 70-80 cm, and 90-100 cm.
l For 1.5-m PVC tubes: O-10 cm, 20-30 cm, 45-55
Soi] parameter
Value
cm, 70-80 cm, 95-105 cm, 120-130 cm, and 140-150
cm.
Total carbon (ppm)
5100
Plants were harvested after 7 weeks for the 0.5-m
Total nitrogen (ppm)
380
PVC tubes, 9 weeks for the 1.0-m PVC tubes, and 12
Minerai nitrogen (ppm)
103
weeks for the 1.5-m PVC tubes.
Total phosphorus (ppm)
75
Available phosphorus (ppm)
4.4
(Olsen)
Results and Discussion
Clay content (%)
6.4
Silt content (S)
7.3
Inoculation by Glonaa mosseue had a clear positive
Sand content (%)
86.3
impact on plant height. After 12 weeks, this effect was
pH (KW
7.0
even more noticeable on plants grown in PVC tubes
pH 0-W)
7.8
(68% height increase over the control) than on plants
grown in polyethylene bags (34%, Fig. 2). Likewise,
above-ground biomass of inoculated plants grown in
Individuals wcre inoculated during potting with 1
polyethylene bags exceeded the control by 82%.
g of finely tut Vipu ro~~~rric~rlutu roots which were
Plants grown in PVC tubes produced 112% more
thoroughly infected by the endomycorrhizal fungus
G!NJW nmsmc. The inoculum was placed 2-3 cm
deep in the planting hole.
- Inoculated
W C pots
.--_- Control WC pots
Experimental Design
. . . . .
Inocuktted
nursery bags
- - - Control nursery baps
The first experiment had two factors-inoculation (a
noninoculated control, C, and inoculation with
Glmr~s nwsseae, G), and sampling date (1, 2, 3, 4, 6,
8, 10, and 12 weeks). Each treatment was replicated
three times in a completely randomized des@.
The second experiment involved the same factors,
but sampling commenced when the first roots ap-
peared at the bottom of each of the three tube sizes
(0.5, 1.0, and 1.5 m in length). There were
five repli-
cations of each treatment in a completely randomized
design.
Main stem height, dry above-ground biomass, root
length, and number of nodules were measured for
both experiments. The percentage of roots infected
ohJ'J"""'I
0
1
2
3
4
5
6
7
x
9
10
II
12
with endomycorrhiza was estimated with a 10x mi-
WlXkS
croscope after staining with Trypan blue in lac-
tophenol (Phillips and Hayman 1970). In the first
Figure 2. Height of the principal stem of
experiment, Ibis was done using 100 pieces of root
biu albida as a function of age, inoculation by
fragments, each 1 cm long, chosen randomly from the
Glomus mosseae, and culture conditions.
153
above-ground biomass than the noninoculaled control
Inoculation at the time of outplanting caused nec-
grown in bags. This is because the limited volume of
rosis of the taproot on 20% of the plants. Plants thus
the bags suppressed root growth after the 8th week,
affected developed 2-6 secondary roots. Inoculating
whereas the larger PVC tubes allowed unrestricted
the plants 2-3 weeks after outplanting may have two
root development up to the 12th week.
advantages, i.e., a well-developed root system would
Besides evidence of a slight depressive effect on
ensure a good infection, and the well-formed taproot
1-week-old plants, inoculation by C/on~~s nlos,seue
would not be injured.
had no effect on taproot elongation. Root length in
Twelve weeks is the minimum time required in
polyethylene bags averagcd 32 cm at 12 weeks. At
the nursery for F. albidu. These data show that, in this
this time, limited growing space caused the roo1.s to
time, the average seedling grown in I-L pots would
coil up at the bottom. In the PVC tubes, where taproot
have a 32-cm taproot and a root biomass of 0.75 g for
growth was unhindered, root lengths averaged 47 cm
the noninoculated control or 1.08 g for inoculated
in 7 weeks, 9.5 cm in 9 weeks, and 143 cm in 12
plants. TO reduce or eliminate production time in the
weeks. Inoculated plants in polyethylene bags pro-
nursery and to take advantage of the growth poten-
duced 44% more root biomass than the control,
tials demonslrated by these experiments, use of larger
whereas those in PVC tubes yielded 57% more root
containers, or even direct seeding, is a preferable
biomass than the control (Fig. 3). This difference is
alternative.
strongly linked to the large increase in fibrous roots
Nodule counts were taken after the second week,
observed on the inoculated plants. This increase
evi-
and correlated positively with root development. In-
dently resulted in incrcased minera1 absorption ca-
oculation by Glor~s rnossecIe greatly enhanced spon-
pacity which led to growth variations among the
taneous nodulation by Bra~vrJ~i~obim (Dreyfus and
treatments. With the exception of plant height, other
Dommergues 1981) already present in the soil. Co-
growth parameters measured were greater than those
lonna et al. (1990a and 1990b) and Ducousso (1990)
recorded by Gupta et al. (1973) at equivalent ages.
suggested that this effect is due to better phosphorous
This could be duc to differences in growth contiitions,
nutrition resulting from infection with endo-
growth period, and/or genotype.
mycorrhiza.
Soi1 volume had a positive effect on planr develop-
ment, but the degree of development depended on
3.0 -
- I n o c u l a t e d P V C p o t s
whether the plants were inoculated. For inoculated
----- Control PVC pots
plants, the quant@ of available phosphorus and BIÛ-
~vrhirohim already in the soi1 (which would in-
. . . . . . . . .
Inocuhted nursery bags
1.5
crease with increasing soi1 volumes), affected the
- - - Control nursery bags
degree of nodulation in the larger PVC tubes. On
noninoculated plants, however, seedlings grown in
-
5 2.0 -
larger volumes of soi1 had fewer nodules than plants
prown in I-L bags. This could be because nitrogen
E
.s
availability was sufficient in the PVC tubes but
lim-
BB 1.5 -
ited in the bags.
L-2
For the noninoculated plants produced in bags, the
z
s
rate of contamination by local endomycorrhizal fungi
0
2 1.0 -
varied with plant age, i.e., 0% for individuals at 1, 2,
3, and 4 weeks, and 40% (maximum) for 12-week-old
plants. No endomycorrhiza was observed on non-
inoculated plants grown in PVC tubes. Since the soi1
0.5 -
used was not sterilized at the beginning of the experi-
ment, the appearance of endomycorrhizal contami-
- .fl
OI’ ’ ’ r-r ’ ’ ’ ’ ’ ’ IJ
riants would be expected. The absence of infection of
0
I
2 3 4 5 6 7 8 9 ‘0 II 12
plants raised in PVC tubes remains unexplained.
Weeks
After 6 weeks, 90% of plants raised in bags
showed signs of endomycorrhizal infection. One
Figure
Dry root mass of Faidherbia albida a s a
week after inoculation, the first appressoria and
intra-
function of age, inoculation by Glonzus mosseae,
root hyphae were noticeable. The fïrst arbuscules
and culture conditions.
were visible in the second week of culture. The rate
154
of infection increased steadily until the 6th week of
References
culture, and then stabilized between 79-90%.
In the PVC tubes, infection rate decreased with
Colonna, J.P., DUCOUSSO, M., and Badji, S. 1990a.
depth. No endomycorrhiza was observed below
Establishment in a sterilized Dior soi1 of a tripartite
70-80 cm. Endomycorrhizal infection was profuse at
symbiosis:
Acuciu
s~rlc:ul-Rhirohirtnl s p .
O-10 cm where it was 76% at week 7,82% at week 9,
ORS.~OO~-G~~~ZU~
n~~seue. Bulletin IGSM 18:105-l
and 95% at week 12. At 20-30 cm, a more moderate
1 1.
endomycorrhizal development occurred-6% at
week 7, 12% at week 9, and 41% at week 12. Virtually
Colonna, J.P., DUCOUSSO, M., and Badji, S. 1990b.
a11 of the roots infected by Glun~ti n~nsseac were
(In press.) Peut-on améliorer le fonctionnement de
located in the Upper part of the plant root system.
I’Acuciu senepd (L.) Willd. et du modèle symbioti-
It is quite possible that this temperate variety of
que “‘Acuciu sene,~ul-R/li=ohirrm”
? Physiologie des
C/~~HU nmssene would not endure extreme variations
arbres et arbustes en zones arides et semi-arides.
in surface soi1 temperature typical in the Sahelian dry
Nancy, France.
season. If an introduced strain happens to survive, its
ability to infect new roots at depth would diminish as
Cornet, F. 1982. Recherches préliminaires sur la
the root system continued to develop at depth. These
symbiose de deux Acaceae tropicaux (A. ruddiurm
results explain, at least in part, the poor results of the
Savi and A. holosericeu
A. Cunn.) avec Rhkobinnz sp
inoculation trials carried out in Senegal with Gkm~~s
et un champignon endomycorrhizien Clornus n~~seue
~IIOSSCUC (Cornet 1982, Cornet et al. 1982, Jaques
Nicol. et Gerd.) DEA Thesis, University of Lyon,
1986).
Lyon, France. No. 1,58 pp.
Cornet, F., Dieni, H.G., and Dommergues, Y.R.
1982. Effet de l’inoculation avec Glonurs nmsseue sur
Conclusion
la croissance d’Acuciu holosericeu en pépiniere et
après transplantation sur le terrain. Pages 287-293
in
Resuhs of the effects of cndomycorrhizal inoculation
Les mycorrhizcs, partie intégrante de la plante: biolo-
on growth of F. ul/>idu seedlings illustrate the impor-
gie et perspective d’utilisation (S. Gianninazzi and
tance of infection in improving the silviculture of this
Gianninazzi-Pearson, M., eds.). France: Institut na-
species. Positive effects on growth parameters
tional de la recherche agronomique.
emerged following inoculation by Clonrrrs nlosseu~
and were enhanced when larper containers were used.
CTFT (Centre technique forestier tropical). 1988.
WC bclieve that successful manipulation of mycor-
Fuidherhiu ulhiclu. (Del.) A. Chev. (Synonyme: Acu-
rhizal infection in F. ulhido in the field could lead to
ciu ulhidu Del.) Monographie. C.T.F.T., Nogent-sur-
spectacular results.
Marne. France: CTFT. 72 pp.
The failure of endomycorrhizal fungi to develop at
greater depths, even under optimal moisture condi-
Dreyfus, B.L, and Dommergues, Y.R. 1981. Nodula-
tions, requires further investigation. As in the case of
tion of Acmiu species by fast and slow growinp tropi-
the inoculation trials undertaken in Senegal,
utiliza-
cal strains of rhizobium. Applied Environmental
tion of temperate strains of Glonzrrs ~IOSSEUC may ex-
Microbiology 41(1):97-99.
plain the limited benelits demonstrated here. In
future, research should not be limited to the surface
DUCOUSSO, M. 1990. Importance des symbioses
horizons only , as is often the case, but also caver the
racinaires pour l’utilisation des acacias en Afrique de
mycorrhizal infection at greater depths. Roots of F.
l’Ouest. Thesis, University of Lyon. Lyon. France.
u/~hidu in Senegal have been found at depths attaininp
260 pp.
34 m (Dupuy and Dreyfus, these proceedings).
Collection and conservation of endomycorrhizal
Gupta, R.K., Saxena, S.K., and Dutta, B.K. 1973.
fungi of F. ul/>idu is important. Also, improved
Germination, seedling behaviour and photomass of
methods for producing suflîcient quantities of inoc-
some acacias in the nursery stage. Indian Forester
ulum for nurseries is essential. Inoculation techniques
99(6):352-3X
should emphasize development of controlled infection
at depths using selecrcd strains which cari suc-
Jacques, D. 1986. Rapport sur les recherches effec-
cessfully compete with wild types already in the soil.
tuées entre le 14 octobre 1984 et le 2 décembre 1985
155
sur les symbiotes des légumineuses auprès du Centre
Phillips, J.M., and Hayman, D.S. 1970. Improved
national de recherches forestières, Institut
sknégalais
procedure for cleaning roots and staining parasitic
des recherches agricoles. Nogent-sur-Marne, France:
and vesicular-arbuscular mycorrhizal fungi for rapid
Centre technique forestier tropical. 11 pp. (Limited
assessment of infection. Transactions of the British
distribution.)
Mycological Society X5:158.
156
Influence on Growth and Development ! : y, i “’ e ’
c COo&. a)0
M. Ducousso~ and J.P. Colonna
Abstract
eflects of inoculation by Glomus mosseae on nodulation andplant growth, and the development
of the endon~ycorrhiral infection were stadied on Faidherbia albida seedlings. The seedlings were
cuftrrred in either polyethylene ba,ps (vol = f L), or 25-L. 50-L, and 75-L PVC (polyvinyl chloride)
tubes containing nonsterilized soils.
Cotnpared with the noninocoiated control, inoculation with Cilomus mosseae enhanced height
(34% increase b bags and 68% in PVC tubes); above-ground hiotnass production (82% and
112%); root hiomass production (44% and 57%): and nodulation (30% and 263%). Endornycor-
rhkal inoculation did not appear to have any impact. either positive or negative, on taproot
elongation.
Ohservatioru revealed that only the apper part of the plant root systenl was infected and that the
inocalunz did not penetrate deeply into the soil. T~US, it is likely that endonlycorrhizal inoculation of
yormg F. albida will prohahly not have a lasring positive impact in tke field.
Introduction
In the first ex
‘ment, we monitored the effects of
seedling inoculati90
n in polyethylene bags (vol = 1 L),
Faidherbia albida, like most of the Acaceae, is capa-
using standard nursery techniques. In the second
ex-
ble of simultaneously forming nitrogen-fixing nod-
periment, seedlings were cultivated in PVC tubes (25
ules and vesicular arbuscular endomycorrhizae
cm in diameter) of various lengths. This experiment
(VAM) on its roots (Ducousso 1990). These infections
represented an intermediate step between the nursery
have been shown to improve seedling development,
conditions (i.e., bags) and Iield conditions by allow-
and have been the focus of studies under controlled
ing observation of root systems and mycorrhizal
de-
conditions in the laboratory and the nursery. Efforts
velopment on plants growing in a larger volume of
to successfully extend these beneficial effects to trans-
soil.
planted seedlings have failed. Outplantings of
Acacia
holosericea, Acacia senegal, and Acacia raddiana in
Senegal demonstrated that beneficial effects of endo-
Materials and Methods
mycorrhizal inoculation diminished after 1 or 2 years.
Interest in F. albida as an element of Sahelian
F. albida seeds (provenance 9012709, DRPF/ISRA,
agroforestry systems (CTFI’ 1988) has stimulated re-
Dakar, Senegal) were pretreated with concentrated
search on mycorrhizal infection on this species in the
sulfuric acid for I h, rinsed well with tap water and
field and its effect on growth. Two experiments were
then germinated for 48 h on moist Sand. After ger-
simultaneously carried out on nonsterilized soi1 rep-
mination, seed coats were removed and the seedlings
resentative of F. albida park zones in Senegal.
were planted in the nursery in either polyethylene
1. Labomtoire de microbiologie forestière. Direction des recherches sur les productions forestières (DRPF). Institut s&égrlnis de recherches
agricoles (ISRA). Ddkdr,Senegal.
2. Laboratoire de biologie et physiologie végétative. ORSTOM, Dakar, Senegdl.
Ducousso, M., and Colonnn, J.P. 1992. Endomycorrhiza infection in young Frri~Wer&~ &Xr: inlluence on growth and development. Pages 151-
156 NI /%r//rcr/~hr ahidr in the West Africnn semi-urid tropics: proceedings of a workshop, 22-26 Apr 1991. Ninmey. Niger (Vandenkldt. R.J.,
ed.). P;wvzheru. A.P. 502 324. Indix Internotionel Crops Research Inrtitute for the Semi-Arid ‘Tropics: and Nairobi. Kenya: Interndtiondl Centre
for Research in Agroforestry.
151
Figure 1. A. Experimental set up showing W C tubes of various lengths 6 weeks after sowing. B. Root
growth in 1.0-m W C tubes 9 weeks after sowing. Five noninoculated plants (right) and five inoculated
plants (left). C. Mycorrhizal infection in S-week-old plants grown in 1-L bags. (Note root coiling.) On the
second plant to the left, taproot branching caused early infection. D. Nodules on roots.
152
bags (vol = 1 L) or in 0.5-m (vol = 25 L), 1.0-m (vol =
root system of each plant. For very young seedlings,
50 L), or 1.5-m (vol = 7.5 L) PVC tubes (25 cm in
samples were taken from Ihe bulked root systems of
diameter) (Fig. 1). All pots were tîlled with sifted
all sampled plants.
Deck soi] (Table 1). Plants were watered daily
In the second experiment, all roots present at the
Woughout thc duration of the experiments.
following depths were observed:
l For 0.5-m PVC tubes: O-10 cm, 20-30 cm, and
40-50 cm.
Tuble 1. Principal physico-chemical characteristics
l For 1.0-m PVC tubes: O-10 cm, 20-30 cm, 45-55
of Deck soi& Bambey, Senegal, 1990.
cm, 70-80 cm, and 90-100 cm.
l For 1.5-m PVC tubes: O-10 cm, 20-30 cm, 45-55
Soi] parameter
Value
cm, 70-80 cm, 95-105 cm, 120-130 cm, and 140-150
cm.
Total carbon (ppm)
5100
Plants were harvested after 7 weeks for the 0.5-m
Total nitrogen (ppm)
380
PVC tubes, 9 weeks for the 1.0-m PVC tubes, and 12
Minerai nitrogen (ppm)
103
weeks for the 1.5-m PVC tubes.
Total phosphorus (ppm)
75
Available phosphorus (ppm)
4.4
(Olsen)
Results and Discussion
Clay content (%)
6.4
Silt content (S)
7.3
Inoculation by Glonaa mosseue had a clear positive
Sand content (%)
86.3
impact on plant height. After 12 weeks, this effect was
pH (KW
7.0
even more noticeable on plants grown in PVC tubes
pH 0-W)
7.8
(68% height increase over the control) than on plants
grown in polyethylene bags (34%, Fig. 2). Likewise,
above-ground biomass of inoculated plants grown in
Individuals wcre inoculated during potting with 1
polyethylene bags exceeded the control by 82%.
g of finely tut Vipu ro~~~rric~rlutu roots which were
Plants grown in PVC tubes produced 112% more
thoroughly infected by the endomycorrhizal fungus
G!NJW nmsmc. The inoculum was placed 2-3 cm
deep in the planting hole.
- Inoculated
W C pots
.--_- Control WC pots
Experimental Design
. . . . .
Inocuktted
nursery bags
- - - Control nursery baps
The first experiment had two factors-inoculation (a
noninoculated control, C, and inoculation with
Glmr~s nwsseae, G), and sampling date (1, 2, 3, 4, 6,
8, 10, and 12 weeks). Each treatment was replicated
three times in a completely randomized des@.
The second experiment involved the same factors,
but sampling commenced when the first roots ap-
peared at the bottom of each of the three tube sizes
(0.5, 1.0, and 1.5 m in length). There were
five repli-
cations of each treatment in a completely randomized
design.
Main stem height, dry above-ground biomass, root
length, and number of nodules were measured for
both experiments. The percentage of roots infected
ohJ'J"""'I
0
1
2
3
4
5
6
7
x
9
10
II
12
with endomycorrhiza was estimated with a 10x mi-
WlXkS
croscope after staining with Trypan blue in lac-
tophenol (Phillips and Hayman 1970). In the first
Figure 2. Height of the principal stem of
experiment, Ibis was done using 100 pieces of root
biu albida as a function of age, inoculation by
fragments, each 1 cm long, chosen randomly from the
Glomus mosseae, and culture conditions.
153
above-ground biomass than the noninoculaled control
Inoculation at the time of outplanting caused nec-
grown in bags. This is because the limited volume of
rosis of the taproot on 20% of the plants. Plants thus
the bags suppressed root growth after the 8th week,
affected developed 2-6 secondary roots. Inoculating
whereas the larger PVC tubes allowed unrestricted
the plants 2-3 weeks after outplanting may have two
root development up to the 12th week.
advantages, i.e., a well-developed root system would
Besides evidence of a slight depressive effect on
ensure a good infection, and the well-formed taproot
1-week-old plants, inoculation by C/on~~s nlos,seue
would not be injured.
had no effect on taproot elongation. Root length in
Twelve weeks is the minimum time required in
polyethylene bags averagcd 32 cm at 12 weeks. At
the nursery for F. albidu. These data show that, in this
this time, limited growing space caused the roo1.s to
time, the average seedling grown in I-L pots would
coil up at the bottom. In the PVC tubes, where taproot
have a 32-cm taproot and a root biomass of 0.75 g for
growth was unhindered, root lengths averaged 47 cm
the noninoculated control or 1.08 g for inoculated
in 7 weeks, 9.5 cm in 9 weeks, and 143 cm in 12
plants. TO reduce or eliminate production time in the
weeks. Inoculated plants in polyethylene bags pro-
nursery and to take advantage of the growth poten-
duced 44% more root biomass than the control,
tials demonslrated by these experiments, use of larger
whereas those in PVC tubes yielded 57% more root
containers, or even direct seeding, is a preferable
biomass than the control (Fig. 3). This difference is
alternative.
strongly linked to the large increase in fibrous roots
Nodule counts were taken after the second week,
observed on the inoculated plants. This increase
evi-
and correlated positively with root development. In-
dently resulted in incrcased minera1 absorption ca-
oculation by Glor~s rnossecIe greatly enhanced spon-
pacity which led to growth variations among the
taneous nodulation by Bra~vrJ~i~obim (Dreyfus and
treatments. With the exception of plant height, other
Dommergues 1981) already present in the soil. Co-
growth parameters measured were greater than those
lonna et al. (1990a and 1990b) and Ducousso (1990)
recorded by Gupta et al. (1973) at equivalent ages.
suggested that this effect is due to better phosphorous
This could be duc to differences in growth contiitions,
nutrition resulting from infection with endo-
growth period, and/or genotype.
mycorrhiza.
Soi1 volume had a positive effect on planr develop-
ment, but the degree of development depended on
3.0 -
- I n o c u l a t e d P V C p o t s
whether the plants were inoculated. For inoculated
----- Control PVC pots
plants, the quant@ of available phosphorus and BIÛ-
~vrhirohim already in the soi1 (which would in-
. . . . . . . . .
Inocuhted nursery bags
1.5
crease with increasing soi1 volumes), affected the
- - - Control nursery bags
degree of nodulation in the larger PVC tubes. On
noninoculated plants, however, seedlings grown in
-
5 2.0 -
larger volumes of soi1 had fewer nodules than plants
prown in I-L bags. This could be because nitrogen
E
.s
availability was sufficient in the PVC tubes but
lim-
BB 1.5 -
ited in the bags.
L-2
For the noninoculated plants produced in bags, the
z
s
rate of contamination by local endomycorrhizal fungi
0
2 1.0 -
varied with plant age, i.e., 0% for individuals at 1, 2,
3, and 4 weeks, and 40% (maximum) for 12-week-old
plants. No endomycorrhiza was observed on non-
inoculated plants grown in PVC tubes. Since the soi1
0.5 -
used was not sterilized at the beginning of the experi-
ment, the appearance of endomycorrhizal contami-
- .fl
OI’ ’ ’ r-r ’ ’ ’ ’ ’ ’ IJ
riants would be expected. The absence of infection of
0
I
2 3 4 5 6 7 8 9 ‘0 II 12
plants raised in PVC tubes remains unexplained.
Weeks
After 6 weeks, 90% of plants raised in bags
showed signs of endomycorrhizal infection. One
Figure
Dry root mass of Faidherbia albida a s a
week after inoculation, the first appressoria and
intra-
function of age, inoculation by Glonzus mosseae,
root hyphae were noticeable. The fïrst arbuscules
and culture conditions.
were visible in the second week of culture. The rate
154
of infection increased steadily until the 6th week of
References
culture, and then stabilized between 79-90%.
In the PVC tubes, infection rate decreased with
Colonna, J.P., DUCOUSSO, M., and Badji, S. 1990a.
depth. No endomycorrhiza was observed below
Establishment in a sterilized Dior soi1 of a tripartite
70-80 cm. Endomycorrhizal infection was profuse at
symbiosis:
Acuciu
s~rlc:ul-Rhirohirtnl s p .
O-10 cm where it was 76% at week 7,82% at week 9,
ORS.~OO~-G~~~ZU~
n~~seue. Bulletin IGSM 18:105-l
and 95% at week 12. At 20-30 cm, a more moderate
1 1.
endomycorrhizal development occurred-6% at
week 7, 12% at week 9, and 41% at week 12. Virtually
Colonna, J.P., DUCOUSSO, M., and Badji, S. 1990b.
a11 of the roots infected by Glun~ti n~nsseac were
(In press.) Peut-on améliorer le fonctionnement de
located in the Upper part of the plant root system.
I’Acuciu senepd (L.) Willd. et du modèle symbioti-
It is quite possible that this temperate variety of
que “‘Acuciu sene,~ul-R/li=ohirrm”
? Physiologie des
C/~~HU nmssene would not endure extreme variations
arbres et arbustes en zones arides et semi-arides.
in surface soi1 temperature typical in the Sahelian dry
Nancy, France.
season. If an introduced strain happens to survive, its
ability to infect new roots at depth would diminish as
Cornet, F. 1982. Recherches préliminaires sur la
the root system continued to develop at depth. These
symbiose de deux Acaceae tropicaux (A. ruddiurm
results explain, at least in part, the poor results of the
Savi and A. holosericeu
A. Cunn.) avec Rhkobinnz sp
inoculation trials carried out in Senegal with Gkm~~s
et un champignon endomycorrhizien Clornus n~~seue
~IIOSSCUC (Cornet 1982, Cornet et al. 1982, Jaques
Nicol. et Gerd.) DEA Thesis, University of Lyon,
1986).
Lyon, France. No. 1,58 pp.
Cornet, F., Dieni, H.G., and Dommergues, Y.R.
1982. Effet de l’inoculation avec Glonurs nmsseue sur
Conclusion
la croissance d’Acuciu holosericeu en pépiniere et
après transplantation sur le terrain. Pages 287-293
in
Resuhs of the effects of cndomycorrhizal inoculation
Les mycorrhizcs, partie intégrante de la plante: biolo-
on growth of F. ul/>idu seedlings illustrate the impor-
gie et perspective d’utilisation (S. Gianninazzi and
tance of infection in improving the silviculture of this
Gianninazzi-Pearson, M., eds.). France: Institut na-
species. Positive effects on growth parameters
tional de la recherche agronomique.
emerged following inoculation by Clonrrrs nlosseu~
and were enhanced when larper containers were used.
CTFT (Centre technique forestier tropical). 1988.
WC bclieve that successful manipulation of mycor-
Fuidherhiu ulhiclu. (Del.) A. Chev. (Synonyme: Acu-
rhizal infection in F. ulhido in the field could lead to
ciu ulhidu Del.) Monographie. C.T.F.T., Nogent-sur-
spectacular results.
Marne. France: CTFT. 72 pp.
The failure of endomycorrhizal fungi to develop at
greater depths, even under optimal moisture condi-
Dreyfus, B.L, and Dommergues, Y.R. 1981. Nodula-
tions, requires further investigation. As in the case of
tion of Acmiu species by fast and slow growinp tropi-
the inoculation trials undertaken in Senegal,
utiliza-
cal strains of rhizobium. Applied Environmental
tion of temperate strains of Glonzrrs ~IOSSEUC may ex-
Microbiology 41(1):97-99.
plain the limited benelits demonstrated here. In
future, research should not be limited to the surface
DUCOUSSO, M. 1990. Importance des symbioses
horizons only , as is often the case, but also caver the
racinaires pour l’utilisation des acacias en Afrique de
mycorrhizal infection at greater depths. Roots of F.
l’Ouest. Thesis, University of Lyon. Lyon. France.
u/~hidu in Senegal have been found at depths attaininp
260 pp.
34 m (Dupuy and Dreyfus, these proceedings).
Collection and conservation of endomycorrhizal
Gupta, R.K., Saxena, S.K., and Dutta, B.K. 1973.
fungi of F. ul/>idu is important. Also, improved
Germination, seedling behaviour and photomass of
methods for producing suflîcient quantities of inoc-
some acacias in the nursery stage. Indian Forester
ulum for nurseries is essential. Inoculation techniques
99(6):352-3X
should emphasize development of controlled infection
at depths using selecrcd strains which cari suc-
Jacques, D. 1986. Rapport sur les recherches effec-
cessfully compete with wild types already in the soil.
tuées entre le 14 octobre 1984 et le 2 décembre 1985
155
sur les symbiotes des légumineuses auprès du Centre
Phillips, J.M., and Hayman, D.S. 1970. Improved
national de recherches forestières, Institut
sknégalais
procedure for cleaning roots and staining parasitic
des recherches agricoles. Nogent-sur-Marne, France:
and vesicular-arbuscular mycorrhizal fungi for rapid
Centre technique forestier tropical. 11 pp. (Limited
assessment of infection. Transactions of the British
distribution.)
Mycological Society X5:158.
156