AgroforestrySysterns 14: 183-191. 1991. 0 ...
AgroforestrySysterns 14: 183-191. 1991.
0 199 1 Kluwer Academic Publishers. Prinled in rhe Nerherlunrls.
Vegetative propagation studies of gum arabic trees.
‘!.
:
1. Propagation of Acacia senegal (L.) Willd. using lignified
..:
cuttings of small diameter with eight nodes
S. BADJI’,*, 1. NDIAYE3, P. DANTHU4 and J.P. COLONNA’*
’
Centre ORSTOM, BP 1386, Dakar, Sénégal;
2 Direcrion
des E;aux et Foréts, Dakar, Sénégal;
) Laboratoire de Morphogénèse Végémle, Université
d’Aix-Marseille III; 3 Direction des
Recherches sur les Productions Forestières (ISRA), Dakar, Sénégal; * Aulhorfor corresponderlce
Key words: gum arahic tree, Acacia senegal, vegetative propagation, cutting, Senegal, Africa
Abstract. In ordcr to study and monitor rates of rooting, callusing and survival, small
diameter stem cuttings (less than 0.4 cm) with eight nodes (12-14 cm long) were taken
. . . .
from trees in the field at different times of the year in tests with small hatches of cuttings.
Among the four tested suhstrates, well drained crushed hasalt powder placed on a bed of
grave1 was the best rooting medium. Rooting was generally poor or even non-existent with
this type of cutting, but the presence of leaves both promoted rooting and significantly
(using Chi square test) improved survival of the cutting. Four leaves were suffïcient to assure
the necessary metdbolic functions. Only stem cuttings collected during the rainy season gave
roots and then, only whcn hormonal trcatments were applied to the cuttings. 8%-IBA
resultrd in significantly berter rooting than did 17%-IBA, 0.2%-NAA and 1%-IAA. With 8%-
IBA, the rate of rooting varied hctween SO and 70% for Iea.fy cuttings collected in the rainy
season. Hormonal treatments had a significant effect on the survival rate of the stem cuttings
during the two months observation period. Furthcr invcstlgations arc bcing conducted with
different types of cuitings.
Kesumé. Des boutures de huit noeuds (12 à 14 cm de long) et de faible diamètre (inférieur
ti 0.4 cm) ont été prélevées au champ, sur des arbres adultes, à diverses périodes de l’année
en vue d’étudier leurs taux d’enracinement, de formation de cals et de survie. La poudre de
basalte concassée sur lit de gravier, avec un bon drainage, s’est révélée comme le meilleur
substrat. Avec ce type de bouture, la présence de feuilles parait absolument indispensable
pour obtenir un enracinement. Quatre feuilles sont suffisantes pour assurer le rôle trophique
qui est probablement le leur. La néo-formation de racines n’est apparue que sur les boutures
prélevées durant la saison des pluies. Sans traitement hormonal les boutures du type étudié
n’ont donné aucun résultat. L’AIB-8% en poudre se révèle meilleur que I’AIB-2% I‘ANA-
0.2% et I’AIA-1%. Avec I’AIB-8%, les taux d’enracinemenr vont de 50 à 70% si le substrat.
l’hygrométrie, la présence de feuilles et la période de prélévement sont convenables.
1. Introduction
Sahelian ecosystems have been severely damaged by the combined effects
of extended drought and the excessive exploitation of natural resources by
mari and livestock. Leguminous Woody perennials play a part in the soi1
conservation and enrichment, in the reconstitution of vegetative caver and
(rooting), the number of cuttings that had callused without roots (callusing)
and the number of cuttings surviving without roots and calluses (survival)
was determined (Fig. 2). Evidently, the number of ail (total) surviving
‘i”i~~iij~i~~i~:jliji’i’:i:’ ‘.S I:
cuttings is ‘survival fcallusing Srooting’.
., :,j .,.. ‘.,.”
.,:.: ‘1 ;..‘.: : .,.
<
:
‘~.
2.1. Preliminav experiment 1: appropriate substrate
. . . . . .<.i,‘I::”
This experiment on substrates comprised four treatments: 1 -- sterilized
. .
Dior type soi1 [Maignien, 19651, 2 - sterïlized mixture (l-l, volume) of
.:
i
Dior soi1 and decomposed sawdust, 3 - Fertiss* turf, 4 -powder (granulo-
metry of coarse-grained Sand) of crushed basalt (layer 7 cm deep) on a bed
of grave& treated with benlate. Cuttings for this experiment were collected
in early October; they had conserved one active leaf per cutting and were
treated by IBA-2%. One hundred stem cuttings by treatment were ob-
served. For any one treatment, there were five pots of twenty stem cuttings.
2.2. Preliminary combined experiment 2:presence of leaves, periods of
collection, hormonal trearments
The effects of three factors were observed. These factors were:
- ‘presence of leaves’ with hvo modalities (L =leaf?y cuttings, NL =leafless
cuttings);
- ‘periods of collection’ with 4 dates (November 2 = early dry season,
March 6 = middle dry season, May 27 = early rainy season, July 29 =
middle rainy season.);
- ‘hormonal treatments’ with 5 treatments (control without hormone, IBA
8% as Rhizopon AA8 *, IBA 2% as Rhizopon AA2*, IAA 1% as
Rhizopon Al*, NAA 0.2% as Rhizopon BO, 2*).
For each date of collection, there was one wooden box by hormonal
treatment as specified in Fig. 1; each box contained a plot of 10 leafy
cuttings (L) and a plot of 10 leafless cuttings (NL); the five wooden boxes
(one by hormonal treatment) contained together 50 leafy cuttings and 50
leafless cuttings.
Consequently, for the four dates of collection, there were 400 cuttings
(forty plots of ten) divided into 200 leafy cuttings and 200 leafless cuttings.
2.3. kxperiment 3: confirmation test
The best of the preceding treatments were applied in a third test, one year
later, in order to confirm whethcr the results could be reproduced. The
stem cuttings were taken in August, immediately treated as outlined ahove
* Ets PUTEAUX: 8 Place de la Loi, 78150 Lc Chcsnay (Fr.).
I
,<‘Z’.
CONTROL
IBA 2 %
IBA a %
IAA 1 %
:::,
Fig. 1. ~xpe~Inentdl
arrangement, with number of cuttings, for each oi thc four “Datca OI
C’ollection”. L =leafy cuttings, NL =leafless cuttings.
and then planted i n propagators containing crusheci basalt 1.111 :I I~ci 01
gravel. Propagators were put in the greenhouse under mist (WC ‘Mcthod~~j.
T‘hree treatments were compared: l/ control without hormone: 2,’ 113A-S’!W:
3; L~~-0.3%. Each treatment was applied to sixty cuttings divided irr
three replicates.
3. Results and discussion
l:or the IWO first experiments, Chi square (x‘) test [Pearson. 19hhl v.xx
with Yaks’ correction IYates, ! 95 1) if necessary (x-c), Thr
~.%lJ)Joyed
probability that the resulting distribution is due to random effects is gener-
;tlly less than 0.01 implying that the affects of trratments were significantl!
different from the control. For the third experiment. variante analysis
(Newman-Keuls test at 5%) was used; angular transformation (y = 2 xc
sinus $&j was applied for freqency datas IDagnt3ie, 19751.
clmong the tcsted substrates, thc crushcd Ixtsalt po\\vdrr gave tiw h~gllcst
tcvel of routing, but this was only 1 1% hccausc thc other conditions wcrc
net optimal. Diffcrences with the other treatments were largely significant
(Table 1). This substrate is the best drained one,
preseits rhc Ixst
and
resistance to microorganisms dcveloprnrnt. On the conrrary. Maury f’ungal
mycelium appeared in Fertiss t u r f . T’his mediuni is toc) ricli. ii I:I\\~‘ 2
strong micrcx~rganism proliferation. Such a proliteration wa4 \\‘tbr> dctit-
mental to the survival of cuttings.
‘I’he results arc summarizcd in I:ig. 2. l-itilizatiori 0i tlic Cl11 bqu,uc ti5t
;tllows regrouping of the data corrcspontiin~c to thc levels of cach f;~ctc~~ 10
he analyzed (Schwartz. 1963].
;P-
1ti-l
in thc estahlishment of agroforcstry systems in this semi-arid region.
Among these species, Acuciu senegal (L.) Willd. produces fodder and fire-
wood and has the additional advantage of exuding gum arable a product of
,,;
”
‘1
economic value [ITC, 19833. The species is well adapted to the edapho-
,:.
,.
,.:.
climatic conditions of central and northern Senegal ]Giffard, 1975).
TO assure success with this species, commercial ventures and reforesta-
tion projects Will have to plant more drought resistant and high-yielding
varieties of Acacia senegal. There is also a need for researchers to Select
both the partners, Acacia semguf and Rhizobinrn, of the nitrogen fixing
symbiosis. Selection of Rhizobium bacteria is presently being conducted
]Dreyfus et al., 1981; Badji et al., 19881. As for the tree, it is necessary to
obtain a reproductible method of propagation of the best individuals
available. This calls for reproduction of ind:lviduals selected in nature for
their abilities to produce large quantities of biomass and gum arabic, to
resist drought and heat stress, and to have growth in poor soils.
This study was developed to determine if vegetative propagation by
cuttings from adult Acacia serre& trees is possible and to gave an mitial
idea of the conditions required for rooting.
2. Materials and methods
Thc work was carried out in three experiments at the ‘Direction des
Recherches sur les Productions Forestières de 1’ISRA’ and at the ‘Centre
ORSTOM’ in Dakar, Senegal. ‘The preliminary experiment 1 concerned the
nature of substrates. The preliminary experiment 3 concerned the prcsence
of leaves, the period of collection and hormonal treatments. The third
experiment used the results from the fïrst two experiments.
Stern cuttings were made in the morning by pruning branches of tree
saplings (4 years old) in the field. Selected branches were located in the
upper part of the crown. The lignifieci cuttings were 12-14 cm long and
had a mean diameter less than 0.4 cm. Each cutting contained erght nodes
from the range of the seventh to the fifteenth as numbered lrom the tip ot
the twig.
Stern cuttings were soaked briefly in a 70 mg l--I benlate solution as
fungicide, then tut slantwisc on the lower side and coated with powder
containing phyto-hormones or rhizogenous substances accordin? to the
prescribed treatment. They were thcn immediately planted in thc substrate.
Well-drained earthenwarc pots were used for the substrate experiment.
In the other cases, wooden boxes (SS X 55 X 1 1 cm) with holes at the
bottom to allow adequate drainage were used as propagators. Al1 the
propagators were put in a shaded cold greenhouse, under mist tcn nnnutcs
per heur- during a twelve hour day. The greenhouse temperature was net
regulated and the relative humidity did not fa11 below 70%.
After tvvo months, the number of cuttings that had givcrr ;II IC:I~~ 011c IOCJ~
Inhle 1. Influsnce of ‘substrate‘ on rooting of lignificd. X-no& Aurna .wrq+~/ cutlingh of
< 0.4 cm diamctcl, wittr orlc Id.
~-.----
--.-. ~ .---.
Parametcrs
‘Substratc’ trcatmcnts
Chi square test
---~~
--~
A
13
(‘
D
x’
(1
5
---~-_-.__--__.~.-----~~~ _
_
_
_
Initial numbcr ot cuttings
I OU
100
IOC1
1 O(r -
-.
-
Numher of rooted cuttings
3
-1
0
11
12.3
< 0.0 I
-‘*
-
-
-
- - ~ -
A. sterilized ‘Dior soi]: B. sterilizcd mixture (l-1, v/v) of ‘Dior‘ soi1 and decomposcd
sawdust; C’. Fdss turf’: D. powder of crushed basalt; S. significance; **. highly slgnitïcant.
Presence of letrves. After two months, the 200 leafless stem cuttings didn‘t
give any rooting or callusing. the number of toral surviving cuttings was 73:
for the 200 leafy cuttings, this number WHS 124; this result was very highl)
significant (Chi square = 109.7; u < 0.001). For ‘rooting’, the values bere
0 for the 200 leafless cuttings and 24 for the 200 leafy cuttings; this result
was SO very highly significant (Chi square = 23.5; a < 0.001). For
‘callusing’, the results were 0 and 7, respectiveiy, for lcafless or leafy
cuttings; this difference was just significant (Chi square =5.2; (1 < (1.05).
SO, the retention of some (4) active leaves seems to be necessary ton
these small diameter stem cuttings which do not have very large reserves.
Comparable results are reported in the literature (Reuveni and K~W).
f’~iods or se~~so~~s o/’ collecrion. The results above had shown that cuttings of
small diameter without leaves did net produce roots. Thus, it was only
from leafy cuttings that the effects of period of collection could be estab-
lished (Fig. 2).
Stern cuttings collected in the early rainy season (50 individualsj and in
the middle r-ainy season (50 individuals) had given better ‘rooting’ rates
(26% and 220/0, respectively) than those collected in the early dry seabon
(50 individu&) and in the middle dry season (50 individuals) which had
shown 0% of ‘rooting’. These differences were very highly significant
(corrected Chi square =23.2; a < 0.001). The period of collection was ot
great importance for these leafy type of cuttings of small diameter collected
in the field. The composition of the hormonal pool in the tissues of the
stem cuttings collected at rainy season was probably more favourable fol
‘rooting’ than those of stem cuttings collected at dry season.
The 50 stcm cuttings for each date of collection had givcn respectivel!.
38. 27, 32 antf 27 total surviving stem cuttings after two months; these
differences were not significant (Chi square =6.‘9; u =O.l). SO. thc dates of
collection had no influence
total survival of strm
on the
cuttinp of smaiI
diameter.
1 8 8
NO LEAVES
LEAVES
.'~'
2<‘
A
.~,..~.i.>;i;:i,,::.:,~:.:~~
:..,:...q. . . . . .
<,I. ,, '~\\*<..:<y
'. i::Il'.::l:i:i:!:i'!:::i:::,:$,
.<.<,.', :.:s
..:,,.,;;.‘.“..,‘:t”’
;. ,,
-.:,'
:.;:::.
,:,:
.:.;.:::.$$:(::!,::!:
.‘y:+::::
CONTROL
.;.' .j::.:: '.'. :
.:
100WI6010W
Q
.
.
_
.
.
.
NAA 0.2 Z
tooa06040w0
IAA 1 'fo
IBA 2 %
.
of the hormonal treatments applied. It is the samc for leafy stem cuttings
collected during the dry season. Only leafy stem cuttings collected during
the rainy season had produced roots under the hormonal treatments tested.
The 20 stem cuttings treated by IBA-8% had given 14 individuals with
roots after two months (70 per cent); the rate of ‘rooting’ had risen 30 per
cent for IBA-2%; 15 per cent for NAA-0.2%; 5 per cent for IAA-1% and 0
for the control without hormone. IBA-8% was the best rooting treatment.
Differences between treatments were very highly significant (corrected Chi
square = 29.3; a < 0.001) and reflected similar rates of rooting reported
by others authors [Loreti and Hartmann, 1964; Lundquist and Torrey,
19841.
Results obtained for ‘rooting + callusing’ had sho,wn similar responses
(14, 7, 1, 6 and 0) to the same sequence of treatments from IBA-8% to
control (corrected Chi square =26.2; a < 0.001).
With these stem cuttings collected at rainy season, the most effective
treatment for ‘rooting’ had given the best ‘total surviving’ rate (17/20);
hormonal treatments significantly effected the survival rate (corrected Chi
square -26.2; a < 0.001).
3.3. C~‘onjirnzation experirnent
Rooting (Fig. 3) occurred in:
- 50% of the cases after 8%-IBA powder treatment;
- 10% of the cases after 0.2%NAA powder treatment and
- 0% for control without hormonal treatment.
These significant (Newman-Keuls test) results (Table 2) clearly con-
firmed the previous results of 70%, 15% and 0, respective@, for the same
treatments. The number of roots per rooted cuttings also confirmed that
8%-IBA powder was the best rhizogenous preparation for this type of
Acacia senegal cutting.
4. Conclusions
This study provides preliminary results concerning vegetative propagation
of Acacia sene@ by cuttings. The entire range of these experiments have
shown that vegetative propagation of Atzrcirr setregtrl by stem cutting is
possible. in spite ofa net very high rooting capacity of mis species.
To’give a neo-formation of roots on eight nodes iignified stem cuttirigs
of small diameter, this species appears to nced:
- a well drained rooting medium;
- retention of some active leaves on the cutting;
- collection of cuttings during the rainy seas orilv:
-
treatment with rooting hormone (IBA-8%).
-
,.,:;...‘,
:.
::,.
:.
:,
,’
.
.
. . . .
‘.
1Yl
7Uhk~2. Res~~lts of tria1 n”3 testing thc best çondittons of rooting (hce test). For cach
treatmsnt thcre werc 60 initial cutttngs in threc repl~catcs of 20.
Treatmenti
After two months
Percentage of roored cuttinps
Number of roots per rooted cuttinp
.:.
.
. .
Control (no hormone)
O%C
0 c
X$4, -IBA powder
50% A
12.7 A
0.2% -NAA powder
10% B
3.1 B
Data followcd by different letters arc significantly dtî’fcrent (Newman-Keuls tcht ar 5%)
If these conditions are respected, the rooting rate cari rise 50 to 70%.
Further investigations are proceeding on ihe dynamics of different types
of cuttings.
..:.:..I.
.:::::,.
References
Badji S, Ducousso M, Gueye M and Colonna JP ( 1988) Fixation hologqw de I’azotc et
possibilité de nodulation croisee chez les deux cspeccs d’acacias producteur5 de gomme
dure: Atrrcia senegal L. Willd. et Atzrciu hcrtr K 13r. ~‘x Bcnth. Cornple Rendus ds
l’Académie des Sciences. Pari,, 307. SCr. III. 663---00X
Dagnélie P (lY75) Théories el Méthodes Statistiques, Vol. 2. Pressei Apronomtqucs dc
Gembloux Ed., Gembloux, 563 pp
Dreyfus BL et Dommergues YR (IYXI) Nodulation of Acacia spccies by tast- and S~OU-
growing strains of Rhizobium. Applied Envtronmcntnl Microhiology 41: Y7-YY
Giffard PL (1975) Les Gommiers, essences de reboisement pour les régnons sahéliennes.
Bois et Forêts des Tropiques 16 1: 3-2 1
International Trade Center (1983) The GUI~ Arahic Mnrkct and thc I~cvcloptncnt ()t
Production. UNCTAD/GATT,
Geneve. New York. 170 pp
Loreti F and Hartmann HT (1964) Propagation ot olive trees by rooting Icafy cuttingb
under mist. Proceedings of the American Society l-or Horttcultural Science 85: 257-263
Lundquist R and Torrey JC (1984) The propagation of Casuarina species from rooted stem
cuttings. Botanical Gazette 145(3): 37X-384
Maignien R (1965) Notice explicative. Carte p&loII,gicluc du Sénégal au l/ lOOI)OOO.
ORSTOM Ed., 63 pp
Pcarson ES (1 Y66) Alternative tests fol- hcterog‘*nclty ol variante: somc Monte-Carlo
results. Biometrika 53: 22Y-233
Rcuveni 0 and Waviv M (1981) Importance of lest rctcntion tv rooting oi A\\t)cado cutttngs.
Journal ot thr American Socicty for Horticultural Science lO6(3): 127-l 30
Sçhwartz D ( 1963) Méthodes statistiques h l’usage des midccins ct biologistch. Flammarion
MGdecinc-Sciences, Paris. 3 1 S pp
0 199 1 Kluwer Academic Publishers. Prinled in rhe Nerherlunrls.
Vegetative propagation studies of gum arabic trees.
‘!.
:
1. Propagation of Acacia senegal (L.) Willd. using lignified
..:
cuttings of small diameter with eight nodes
S. BADJI’,*, 1. NDIAYE3, P. DANTHU4 and J.P. COLONNA’*
’
Centre ORSTOM, BP 1386, Dakar, Sénégal;
2 Direcrion
des E;aux et Foréts, Dakar, Sénégal;
) Laboratoire de Morphogénèse Végémle, Université
d’Aix-Marseille III; 3 Direction des
Recherches sur les Productions Forestières (ISRA), Dakar, Sénégal; * Aulhorfor corresponderlce
Key words: gum arahic tree, Acacia senegal, vegetative propagation, cutting, Senegal, Africa
Abstract. In ordcr to study and monitor rates of rooting, callusing and survival, small
diameter stem cuttings (less than 0.4 cm) with eight nodes (12-14 cm long) were taken
. . . .
from trees in the field at different times of the year in tests with small hatches of cuttings.
Among the four tested suhstrates, well drained crushed hasalt powder placed on a bed of
grave1 was the best rooting medium. Rooting was generally poor or even non-existent with
this type of cutting, but the presence of leaves both promoted rooting and significantly
(using Chi square test) improved survival of the cutting. Four leaves were suffïcient to assure
the necessary metdbolic functions. Only stem cuttings collected during the rainy season gave
roots and then, only whcn hormonal trcatments were applied to the cuttings. 8%-IBA
resultrd in significantly berter rooting than did 17%-IBA, 0.2%-NAA and 1%-IAA. With 8%-
IBA, the rate of rooting varied hctween SO and 70% for Iea.fy cuttings collected in the rainy
season. Hormonal treatments had a significant effect on the survival rate of the stem cuttings
during the two months observation period. Furthcr invcstlgations arc bcing conducted with
different types of cuitings.
Kesumé. Des boutures de huit noeuds (12 à 14 cm de long) et de faible diamètre (inférieur
ti 0.4 cm) ont été prélevées au champ, sur des arbres adultes, à diverses périodes de l’année
en vue d’étudier leurs taux d’enracinement, de formation de cals et de survie. La poudre de
basalte concassée sur lit de gravier, avec un bon drainage, s’est révélée comme le meilleur
substrat. Avec ce type de bouture, la présence de feuilles parait absolument indispensable
pour obtenir un enracinement. Quatre feuilles sont suffisantes pour assurer le rôle trophique
qui est probablement le leur. La néo-formation de racines n’est apparue que sur les boutures
prélevées durant la saison des pluies. Sans traitement hormonal les boutures du type étudié
n’ont donné aucun résultat. L’AIB-8% en poudre se révèle meilleur que I’AIB-2% I‘ANA-
0.2% et I’AIA-1%. Avec I’AIB-8%, les taux d’enracinemenr vont de 50 à 70% si le substrat.
l’hygrométrie, la présence de feuilles et la période de prélévement sont convenables.
1. Introduction
Sahelian ecosystems have been severely damaged by the combined effects
of extended drought and the excessive exploitation of natural resources by
mari and livestock. Leguminous Woody perennials play a part in the soi1
conservation and enrichment, in the reconstitution of vegetative caver and
(rooting), the number of cuttings that had callused without roots (callusing)
and the number of cuttings surviving without roots and calluses (survival)
was determined (Fig. 2). Evidently, the number of ail (total) surviving
‘i”i~~iij~i~~i~:jliji’i’:i:’ ‘.S I:
cuttings is ‘survival fcallusing Srooting’.
., :,j .,.. ‘.,.”
.,:.: ‘1 ;..‘.: : .,.
<
:
‘~.
2.1. Preliminav experiment 1: appropriate substrate
. . . . . .<.i,‘I::”
This experiment on substrates comprised four treatments: 1 -- sterilized
. .
Dior type soi1 [Maignien, 19651, 2 - sterïlized mixture (l-l, volume) of
.:
i
Dior soi1 and decomposed sawdust, 3 - Fertiss* turf, 4 -powder (granulo-
metry of coarse-grained Sand) of crushed basalt (layer 7 cm deep) on a bed
of grave& treated with benlate. Cuttings for this experiment were collected
in early October; they had conserved one active leaf per cutting and were
treated by IBA-2%. One hundred stem cuttings by treatment were ob-
served. For any one treatment, there were five pots of twenty stem cuttings.
2.2. Preliminary combined experiment 2:presence of leaves, periods of
collection, hormonal trearments
The effects of three factors were observed. These factors were:
- ‘presence of leaves’ with hvo modalities (L =leaf?y cuttings, NL =leafless
cuttings);
- ‘periods of collection’ with 4 dates (November 2 = early dry season,
March 6 = middle dry season, May 27 = early rainy season, July 29 =
middle rainy season.);
- ‘hormonal treatments’ with 5 treatments (control without hormone, IBA
8% as Rhizopon AA8 *, IBA 2% as Rhizopon AA2*, IAA 1% as
Rhizopon Al*, NAA 0.2% as Rhizopon BO, 2*).
For each date of collection, there was one wooden box by hormonal
treatment as specified in Fig. 1; each box contained a plot of 10 leafy
cuttings (L) and a plot of 10 leafless cuttings (NL); the five wooden boxes
(one by hormonal treatment) contained together 50 leafy cuttings and 50
leafless cuttings.
Consequently, for the four dates of collection, there were 400 cuttings
(forty plots of ten) divided into 200 leafy cuttings and 200 leafless cuttings.
2.3. kxperiment 3: confirmation test
The best of the preceding treatments were applied in a third test, one year
later, in order to confirm whethcr the results could be reproduced. The
stem cuttings were taken in August, immediately treated as outlined ahove
* Ets PUTEAUX: 8 Place de la Loi, 78150 Lc Chcsnay (Fr.).
I
,<‘Z’.
CONTROL
IBA 2 %
IBA a %
IAA 1 %
:::,
Fig. 1. ~xpe~Inentdl
arrangement, with number of cuttings, for each oi thc four “Datca OI
C’ollection”. L =leafy cuttings, NL =leafless cuttings.
and then planted i n propagators containing crusheci basalt 1.111 :I I~ci 01
gravel. Propagators were put in the greenhouse under mist (WC ‘Mcthod~~j.
T‘hree treatments were compared: l/ control without hormone: 2,’ 113A-S’!W:
3; L~~-0.3%. Each treatment was applied to sixty cuttings divided irr
three replicates.
3. Results and discussion
l:or the IWO first experiments, Chi square (x‘) test [Pearson. 19hhl v.xx
with Yaks’ correction IYates, ! 95 1) if necessary (x-c), Thr
~.%lJ)Joyed
probability that the resulting distribution is due to random effects is gener-
;tlly less than 0.01 implying that the affects of trratments were significantl!
different from the control. For the third experiment. variante analysis
(Newman-Keuls test at 5%) was used; angular transformation (y = 2 xc
sinus $&j was applied for freqency datas IDagnt3ie, 19751.
clmong the tcsted substrates, thc crushcd Ixtsalt po\\vdrr gave tiw h~gllcst
tcvel of routing, but this was only 1 1% hccausc thc other conditions wcrc
net optimal. Diffcrences with the other treatments were largely significant
(Table 1). This substrate is the best drained one,
preseits rhc Ixst
and
resistance to microorganisms dcveloprnrnt. On the conrrary. Maury f’ungal
mycelium appeared in Fertiss t u r f . T’his mediuni is toc) ricli. ii I:I\\~‘ 2
strong micrcx~rganism proliferation. Such a proliteration wa4 \\‘tbr> dctit-
mental to the survival of cuttings.
‘I’he results arc summarizcd in I:ig. 2. l-itilizatiori 0i tlic Cl11 bqu,uc ti5t
;tllows regrouping of the data corrcspontiin~c to thc levels of cach f;~ctc~~ 10
he analyzed (Schwartz. 1963].
;P-
1ti-l
in thc estahlishment of agroforcstry systems in this semi-arid region.
Among these species, Acuciu senegal (L.) Willd. produces fodder and fire-
wood and has the additional advantage of exuding gum arable a product of
,,;
”
‘1
economic value [ITC, 19833. The species is well adapted to the edapho-
,:.
,.
,.:.
climatic conditions of central and northern Senegal ]Giffard, 1975).
TO assure success with this species, commercial ventures and reforesta-
tion projects Will have to plant more drought resistant and high-yielding
varieties of Acacia senegal. There is also a need for researchers to Select
both the partners, Acacia semguf and Rhizobinrn, of the nitrogen fixing
symbiosis. Selection of Rhizobium bacteria is presently being conducted
]Dreyfus et al., 1981; Badji et al., 19881. As for the tree, it is necessary to
obtain a reproductible method of propagation of the best individuals
available. This calls for reproduction of ind:lviduals selected in nature for
their abilities to produce large quantities of biomass and gum arabic, to
resist drought and heat stress, and to have growth in poor soils.
This study was developed to determine if vegetative propagation by
cuttings from adult Acacia serre& trees is possible and to gave an mitial
idea of the conditions required for rooting.
2. Materials and methods
Thc work was carried out in three experiments at the ‘Direction des
Recherches sur les Productions Forestières de 1’ISRA’ and at the ‘Centre
ORSTOM’ in Dakar, Senegal. ‘The preliminary experiment 1 concerned the
nature of substrates. The preliminary experiment 3 concerned the prcsence
of leaves, the period of collection and hormonal treatments. The third
experiment used the results from the fïrst two experiments.
Stern cuttings were made in the morning by pruning branches of tree
saplings (4 years old) in the field. Selected branches were located in the
upper part of the crown. The lignifieci cuttings were 12-14 cm long and
had a mean diameter less than 0.4 cm. Each cutting contained erght nodes
from the range of the seventh to the fifteenth as numbered lrom the tip ot
the twig.
Stern cuttings were soaked briefly in a 70 mg l--I benlate solution as
fungicide, then tut slantwisc on the lower side and coated with powder
containing phyto-hormones or rhizogenous substances accordin? to the
prescribed treatment. They were thcn immediately planted in thc substrate.
Well-drained earthenwarc pots were used for the substrate experiment.
In the other cases, wooden boxes (SS X 55 X 1 1 cm) with holes at the
bottom to allow adequate drainage were used as propagators. Al1 the
propagators were put in a shaded cold greenhouse, under mist tcn nnnutcs
per heur- during a twelve hour day. The greenhouse temperature was net
regulated and the relative humidity did not fa11 below 70%.
After tvvo months, the number of cuttings that had givcrr ;II IC:I~~ 011c IOCJ~
Inhle 1. Influsnce of ‘substrate‘ on rooting of lignificd. X-no& Aurna .wrq+~/ cutlingh of
< 0.4 cm diamctcl, wittr orlc Id.
~-.----
--.-. ~ .---.
Parametcrs
‘Substratc’ trcatmcnts
Chi square test
---~~
--~
A
13
(‘
D
x’
(1
5
---~-_-.__--__.~.-----~~~ _
_
_
_
Initial numbcr ot cuttings
I OU
100
IOC1
1 O(r -
-.
-
Numher of rooted cuttings
3
-1
0
11
12.3
< 0.0 I
-‘*
-
-
-
- - ~ -
A. sterilized ‘Dior soi]: B. sterilizcd mixture (l-1, v/v) of ‘Dior‘ soi1 and decomposcd
sawdust; C’. Fdss turf’: D. powder of crushed basalt; S. significance; **. highly slgnitïcant.
Presence of letrves. After two months, the 200 leafless stem cuttings didn‘t
give any rooting or callusing. the number of toral surviving cuttings was 73:
for the 200 leafy cuttings, this number WHS 124; this result was very highl)
significant (Chi square = 109.7; u < 0.001). For ‘rooting’, the values bere
0 for the 200 leafless cuttings and 24 for the 200 leafy cuttings; this result
was SO very highly significant (Chi square = 23.5; a < 0.001). For
‘callusing’, the results were 0 and 7, respectiveiy, for lcafless or leafy
cuttings; this difference was just significant (Chi square =5.2; (1 < (1.05).
SO, the retention of some (4) active leaves seems to be necessary ton
these small diameter stem cuttings which do not have very large reserves.
Comparable results are reported in the literature (Reuveni and K~W).
f’~iods or se~~so~~s o/’ collecrion. The results above had shown that cuttings of
small diameter without leaves did net produce roots. Thus, it was only
from leafy cuttings that the effects of period of collection could be estab-
lished (Fig. 2).
Stern cuttings collected in the early rainy season (50 individualsj and in
the middle r-ainy season (50 individuals) had given better ‘rooting’ rates
(26% and 220/0, respectively) than those collected in the early dry seabon
(50 individu&) and in the middle dry season (50 individuals) which had
shown 0% of ‘rooting’. These differences were very highly significant
(corrected Chi square =23.2; a < 0.001). The period of collection was ot
great importance for these leafy type of cuttings of small diameter collected
in the field. The composition of the hormonal pool in the tissues of the
stem cuttings collected at rainy season was probably more favourable fol
‘rooting’ than those of stem cuttings collected at dry season.
The 50 stcm cuttings for each date of collection had givcn respectivel!.
38. 27, 32 antf 27 total surviving stem cuttings after two months; these
differences were not significant (Chi square =6.‘9; u =O.l). SO. thc dates of
collection had no influence
total survival of strm
on the
cuttinp of smaiI
diameter.
1 8 8
NO LEAVES
LEAVES
.'~'
2<‘
A
.~,..~.i.>;i;:i,,::.:,~:.:~~
:..,:...q. . . . . .
<,I. ,, '~\\*<..:<y
'. i::Il'.::l:i:i:!:i'!:::i:::,:$,
.<.<,.', :.:s
..:,,.,;;.‘.“..,‘:t”’
;. ,,
-.:,'
:.;:::.
,:,:
.:.;.:::.$$:(::!,::!:
.‘y:+::::
CONTROL
.;.' .j::.:: '.'. :
.:
100WI6010W
Q
.
.
_
.
.
.
NAA 0.2 Z
tooa06040w0
IAA 1 'fo
IBA 2 %
.
of the hormonal treatments applied. It is the samc for leafy stem cuttings
collected during the dry season. Only leafy stem cuttings collected during
the rainy season had produced roots under the hormonal treatments tested.
The 20 stem cuttings treated by IBA-8% had given 14 individuals with
roots after two months (70 per cent); the rate of ‘rooting’ had risen 30 per
cent for IBA-2%; 15 per cent for NAA-0.2%; 5 per cent for IAA-1% and 0
for the control without hormone. IBA-8% was the best rooting treatment.
Differences between treatments were very highly significant (corrected Chi
square = 29.3; a < 0.001) and reflected similar rates of rooting reported
by others authors [Loreti and Hartmann, 1964; Lundquist and Torrey,
19841.
Results obtained for ‘rooting + callusing’ had sho,wn similar responses
(14, 7, 1, 6 and 0) to the same sequence of treatments from IBA-8% to
control (corrected Chi square =26.2; a < 0.001).
With these stem cuttings collected at rainy season, the most effective
treatment for ‘rooting’ had given the best ‘total surviving’ rate (17/20);
hormonal treatments significantly effected the survival rate (corrected Chi
square -26.2; a < 0.001).
3.3. C~‘onjirnzation experirnent
Rooting (Fig. 3) occurred in:
- 50% of the cases after 8%-IBA powder treatment;
- 10% of the cases after 0.2%NAA powder treatment and
- 0% for control without hormonal treatment.
These significant (Newman-Keuls test) results (Table 2) clearly con-
firmed the previous results of 70%, 15% and 0, respective@, for the same
treatments. The number of roots per rooted cuttings also confirmed that
8%-IBA powder was the best rhizogenous preparation for this type of
Acacia senegal cutting.
4. Conclusions
This study provides preliminary results concerning vegetative propagation
of Acacia sene@ by cuttings. The entire range of these experiments have
shown that vegetative propagation of Atzrcirr setregtrl by stem cutting is
possible. in spite ofa net very high rooting capacity of mis species.
To’give a neo-formation of roots on eight nodes iignified stem cuttirigs
of small diameter, this species appears to nced:
- a well drained rooting medium;
- retention of some active leaves on the cutting;
- collection of cuttings during the rainy seas orilv:
-
treatment with rooting hormone (IBA-8%).
-
,.,:;...‘,
:.
::,.
:.
:,
,’
.
.
. . . .
‘.
1Yl
7Uhk~2. Res~~lts of tria1 n”3 testing thc best çondittons of rooting (hce test). For cach
treatmsnt thcre werc 60 initial cutttngs in threc repl~catcs of 20.
Treatmenti
After two months
Percentage of roored cuttinps
Number of roots per rooted cuttinp
.:.
.
. .
Control (no hormone)
O%C
0 c
X$4, -IBA powder
50% A
12.7 A
0.2% -NAA powder
10% B
3.1 B
Data followcd by different letters arc significantly dtî’fcrent (Newman-Keuls tcht ar 5%)
If these conditions are respected, the rooting rate cari rise 50 to 70%.
Further investigations are proceeding on ihe dynamics of different types
of cuttings.
..:.:..I.
.:::::,.
References
Badji S, Ducousso M, Gueye M and Colonna JP ( 1988) Fixation hologqw de I’azotc et
possibilité de nodulation croisee chez les deux cspeccs d’acacias producteur5 de gomme
dure: Atrrcia senegal L. Willd. et Atzrciu hcrtr K 13r. ~‘x Bcnth. Cornple Rendus ds
l’Académie des Sciences. Pari,, 307. SCr. III. 663---00X
Dagnélie P (lY75) Théories el Méthodes Statistiques, Vol. 2. Pressei Apronomtqucs dc
Gembloux Ed., Gembloux, 563 pp
Dreyfus BL et Dommergues YR (IYXI) Nodulation of Acacia spccies by tast- and S~OU-
growing strains of Rhizobium. Applied Envtronmcntnl Microhiology 41: Y7-YY
Giffard PL (1975) Les Gommiers, essences de reboisement pour les régnons sahéliennes.
Bois et Forêts des Tropiques 16 1: 3-2 1
International Trade Center (1983) The GUI~ Arahic Mnrkct and thc I~cvcloptncnt ()t
Production. UNCTAD/GATT,
Geneve. New York. 170 pp
Loreti F and Hartmann HT (1964) Propagation ot olive trees by rooting Icafy cuttingb
under mist. Proceedings of the American Society l-or Horttcultural Science 85: 257-263
Lundquist R and Torrey JC (1984) The propagation of Casuarina species from rooted stem
cuttings. Botanical Gazette 145(3): 37X-384
Maignien R (1965) Notice explicative. Carte p&loII,gicluc du Sénégal au l/ lOOI)OOO.
ORSTOM Ed., 63 pp
Pcarson ES (1 Y66) Alternative tests fol- hcterog‘*nclty ol variante: somc Monte-Carlo
results. Biometrika 53: 22Y-233
Rcuveni 0 and Waviv M (1981) Importance of lest rctcntion tv rooting oi A\\t)cado cutttngs.
Journal ot thr American Socicty for Horticultural Science lO6(3): 127-l 30
Sçhwartz D ( 1963) Méthodes statistiques h l’usage des midccins ct biologistch. Flammarion
MGdecinc-Sciences, Paris. 3 1 S pp