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THE USE OF STEM CUTTINGS TO PROPAGATE 

ATRIPLEX NUMMULARIA L. (OLDMAN SALTBUSH) VEGETATIVELY

 

P.J. Malan

Grootfontein Agricultural Development Institute

Private bag X529, Middelburg 5900

N.F.G. Rethman 

Department of Plantproduction and Soil Science

University of Pretoria, Pretoria, 0001



INTRODUCTION

Atriplex nummularia (oldman saltbush) is a naturalised and well known fodder shrub in the arid and semi-arid parts of South Africa.  Stock farmers establish plantations of A. nummularia, to be used as a fodderbank during dry periods when the grazing capacity of natural grazing land is very low (Barnard, 1986).  Differences in palatability caused the need of propagating the more palatable plants, to obtain a more homogeneous stand of palatable plants, which will ensure more effective utilization of A. nummularia plantations.  As the genus Atriplex is dioecious and openpollinated (Osmond, Björkman & Anderson, 1980), a vegetative propagation method was tested.  It was decided to use stem cuttings for vegetative propagation.

According to the literature, similar trials were conducted on other Atriplex (Saltbush) species (Ellern, 1970; Everett, Meeuwig & Robbertson, 1978 and Richardson, Barker, Crofts & Van Epps, 1979).  De Kock (1983) mentioned that it is possible to root stem cuttings of A. nummularia, but did not quantify the success rate.

In this case it can be assumed that the Atriplex species is an easy rooter, as there is some evidence  in the literature (Ellern, 1970 and De Kock, 1983). The specific research objectives were to: identify the optimum season to collect stem cuttings of A. nummularia, see whether the age of the stems plays an important role, determine how the portion of stem used for cuttings affect the rooting and to study the response of A. nummularia to various concentrations of exogenously applied indole-3-butyric acid (IBA).

 

MATERIAL AND METHODS

The cuttings were taken from an existing A. nummularia plantation. Two different plants: one with new growth, since it was cut down to 45 cm. the season before and one with old growth, since it was not cut down the previous season, were used.  This was decided to find out whether the age of the growth would make any difference on the rooting ability of stem cuttings.

For each plant two cutting types were tested: terminal (tip) and subterminal.  The terminal cuttings from the new growth plant were juvenile growth and more herbaceous, while the other cuttings were more semi-hardwood than herbaceous. 

Each cutting type were treated with three hormonal regimes: 0 g.kg-1, 3 g.kg-1 and 8 g.kg-1 IBA.  For each plant, cutting type and hormonal regime, 10 cuttings were used.  All the treatments were executed in four replicates  and replicated over three seasons: summer, autumn and spring.  Which means that for each season 480 cuttings were taken, 240 for each plant and 60 for each replicate, with each replicate consisting of 30 terminal and 30 subterminal cuttings, 10 for each hormonal treatment.

 

RESULTS AND DISCUSSION

Season

Average rooting of cuttings was higher in spring (47%) than in summer (37%), with the autumn (42%) intermediate, as illustrated in Table 1.  During the summer, high temperatures inside the greenhouse together with the high humidity caused disease development in the mist-bench, which contaminated most of the cuttings.  This may have contributed to the low rooting percentage the summer.

Table 1: The influence of season on the rooting percentage of Atriplex nummularia

Cutting type

Summer

Autumn

Spring

Average for terminal cuttings

46

69

75

Average for subterminal cuttings

29

15

18

Total average

37

42

47

The best results as averaged for all treatments, were in spring. Although 47% rooting seems low, it is only the average over all treatments and, within the treatments, rooting success of up to 75% was achieved for terminal cuttings (see Table 1) during spring. It could therefore be recommended that spring is a better season to propagate A. nummularia vegetatively than autumn.  

Plant type

Rooting of the new growth plant was higher than rooting of the old growth plant.  These results are similar to Arya, Toky, Tomar, Singh and Harris (1993) whose study indicated that stem cuttings of juvenile material are the best to propagate Prosopis cineraria(L.) vegetatively. 

For the old growth plant, the terminal cuttings showed acceptable rooting (35%), but not as good as the terminal cuttings of the new growth plant (49%). According to Table 2, the largest difference between the two plant types were in autumn.  During autumn and winter the plants are in a stage of dormancy which may explain the poor (24%) rooting of the old growth plant in autumn.   Rooting percentage of the new growth plant was the highest in autumn. It may be that the new growth reach dormancy at a later stage than the old growth, or that new growth contains higher levels of carbohydrates, nitrogenous compounds and auxins than old growth, as there is a strong relation between these compounds and root formation (Joshi, Sharma, Shamet & Dhiman, 1992).

Table 2: The influence of age of growth on the rooting percentage of Atriplex nummularia

Season

Old growth

New growth

Summer

39

35

Autumn

24

60

Spring

41

53

Average

35

49

Cutting type

In both plants the performance of the subterminal cuttings was not convincing.  In all three seasons rooting of terminal cuttings were higher than rooting of subterminal cuttings. The largest overall average of 75% was in spring as can be seen in Table 3.

Table 3: The influence of cutting type on the rooting percentage of Atriplex nummularia

Season

Terminal cuttings

Subterminal cuttings

Summer

46

29

Autumn

69

15

Spring

75

18

Average

63

21

Hormonal treatment

The 0 g.kg-1 IBA showed an average root initiation of 36%, while the 3- and 8 g.kg-1 IBA showed an average root initiation of 46% and 45% respectively (Table 4).  However, when only the terminal cuttings are evaluated, 3 g.kg-1 IBA gave the highest results in autumn (73%) and spring (81%), with the average of 81% in spring higher than that of any other treatment.    The 0 g.kg-1 IBA treatment gave a 70% rooting success for terminal cuttings, which is promising in the sense that it would be much more economical if A. nummularia can be propagated vegetatively without auxin treatment.  It may be possible to find some A. nummularia plants with the genetic ability to give a rooting percentage above 70%.  Ellern (1970) got a 77% rooting for A. halimus without any hormonal treatment.

Table 4: The influence of hormonal regime on the rooting percentage of Atriplex nummularia

Season

0 g.kg-1 IBA

3 g.kg-1 IBA

8 g.kg-1 IBA

Summer

26

37

49

Autumn

39

46

42

Spring

44

54

43

Average

36

46

45

 

CONCLUSION AND RECOMMENDATIONS

From the results of this experiment it is clear that vegetative propagation of A. nummularia, by stem cuttings, is possible. According to the Response Surface analysis that was done, as the statistical analysis, to find the optimum method for rooting stem cuttings of A. nummularia, the following procedure is recommended: use a plant with new growth (for instance one that was cut down recently and already started new shoot growth), use only terminal stem cuttings of 10 to 15 cm,  treat the cuttings with 3 g.kg-1 IBA and do all of this in the late autumn or spring.  Rooted cuttings can be transplanted into pots containing a mixture of 40% soil, 40% compost and 20% sand.  

More than one mother plant should be used.  The reason being the genetic difference between plants within this species, which may result in different rooting abilities between different plants. Another reason is, to maintain genetic variability, to protect the progeny against pests. If all the new plants are from the same mother plant, they could be highly vulnerable to pests.

 

REFERENCES

ARYA, S., TOKY, O.P., TOMAR, R., SINGH, L. & HARRIS, P.J.C., 1993.  Seasonal variation in auxin-induced rooting of Prosopis cineraria stem cuttings.  The International Tree Crops Journal. 7, 249-259.

BARNARD, S.A., 1986.  Oumansoutbos in die Winterreënvalstreek.  Boerdery in Suid-Afrika. Nr. 140.

DE KOCK, G.C., 1983.  Drought resistant fodder crops. In H.N. Le Houérou (ed.). Browse in Africa. The current state of knowledge.  International livestock centre for Africa, Addis Ababa, Ethiopia.

ELLERN, S.J., 1970.  Rooting cuttings of saltbush (Atriplex halimus L.). In Technical Notes No. 1828 E. Volcani Institute of Agricultural Research, Bet Dagan, Israel.

EVERETT, R.L., MEEUWIG, R.O. & ROBERTSON, J.H., 1978.  Propagation of Nevada    shrubs by stem cuttings.  J. Range Manage.  31, 426-429.

HARTMAN, H.T., KESTER, D.E. & DAVIES, F.T., 1990.  Plant propagation principles and practices, fifth edn.  Prentice Hall, New Jersey.

JOSHI, N.K., SHARMA, S., SHAMET, G.S. & DHIMAN, D.C., 1992.  Studies on the effect of auxin and season on rooting stem cuttings of some important shrubs in nursery beds.  Indian Forster.    892-900.

OSMOND, C.B., BJÖRKMAN, O. & ANDERSON, D.J., 1980.  Physiological processes in plant ecology.  Toward a synthesis with Atriplex.  Ecological studies, Vol. 36.  New York: Springer-Verlag Ed. 

RICHARDSON, S.G., BARKER, J.R., CROFTS, K.A. & VAN EPPS, G.A., 1979.  Factors affecting root of stem cuttings of salt desert shrubs.  J. Range Manage. 32, 280-283.

WEISNER, L.E. & JOHNSON, W.J., 1977.  Fourwing saltbush (Atriplex canescens) propagation techniques.  J. Range Manage. 30, 154-156.

 

Published

Grootfontein Agric Vol 3 No 1 (4-6)