Australian Dry-zone Acacias for Human Food

APN House,CE Harwood

• Editorial: CSIRO PUBLISHING
• Año: 1992
• ISBN:
  9780643102408
• Categoría: Biological Sciences
• Categoría: Botany

Australia's unique and diverse woody flora has become socially, economically and environmentally important in many other countries. The seed of some Acacia species showing promise in planting programs in semi-arid areas has been a part of the traditional diet of Australia's Aboriginal people. The dry seed may be ground to flour, mixed with water and eaten as a paste or baked to form a cake. Forest tree breeding has focussed on wood production, selecting taller, faster-growing varieties.

The same principles of selection and improvement can be applied to improve seed yields and nutritional properties of shrubs. The selection criteria would include seed characters such as taste, seed coat thickness and nutritive value to maximize their food value. The book looks at the possibility of building upon the traditional knowledge of Aboriginal Australians, using modern scientific methods, for the benefit of people in the world's dry areas.

Australian Dry-zone Acacias for Human Food documents the proceedings of a workshop held at Glen Helen, Northern Territory, Australia. The purpose of the meeting was to examine the idea of developing the food value of the seed of Australia's dry-zone acacias.

This book covers a summary of the workshop conlcusions, the invited papers, and recommendations of the working groups.

INVITED PAPERS

Acacia colei ms, south of Halls Creek, Western Australia. Left, tree form; right, detail of pods with seeds. Photos: Lex Thomson.

Acacia tumida, Niger. The bushy habit facilitates the harvesting of seeds. Photo: Lex Thomson.

Australia’s subtropical dry-zone Acacia
species with human food potential

Lex Thomson ¹

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ABSTRACT

Based on reports of their utilization as food by Aborigines and other salient features, this review has identified 44 species of Acacia from Australia’s subtropical dry-zone which have potential for production of human food. Information on each of these species, including important components of their natural distributions (climate and soils), growth characteristics and their taxonomie relationships to other Acacia species has been tabulated. Three species in section Juliflorae, viz. A. colei ms, A. cowleana and A. tutnida, appear to have outstanding potential for production of human food in the Sahelian zone of sub-Saharan Africa. These species have already demonstrated rapid growth and early production of heavy, easily harvested and utilized seed crops when planted on otherwise non-arable lands in West Africa. Other promising Juliflorae acacias for human food include A. adsurgens, A. sp. aff. cowleana and A. oligophleba. Two species in other sections, viz. A. coriacea var. pendula (section Plurinerves) and A. glaucocaesia (a close relative of A. victoriae, section Phyllodineae), have very high potential for production of human food but have yet to be evaluated outside Australia.

There is an urgent requirement for thorough biochemical analyses, especially possible anti-nutritional or toxic components, of the seeds of those species with greatest human food potential. There is also an important need for biosystematic studies to be undertaken on species and species groups of high potential socioeconomic importance (e.g. A. holosericea group, A. tumida, A. coriacea, A. victoriae group). These studies must be based on comprehensive and well-documented seed collections.

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INTRODUCTION

Australia has a vast tropical and subtropical, dry (< 500 mm) zone covering 1.7 x 10⁶ km² (north of 24°S). The 130 Acacia species present in this zone represent an important, but largely untapped genetic resource for reforestation in other tropical, dry parts of the world. A few species, in particular A. colei Maslin & Thomson (manuscript name, fide Maslin & Thomson in prep.) (formerly under the name A. holosericea) and A. tumida, have demonstrated rapid growth and adaptability to difficult and degraded sites in the drought and famine-prone Sahelian zone of west Africa (Cossalter 1987), as well as east Africa (e.g. Somalia and Kenya) and southern Africa (e.g. Zimbabwe, Gwaze 1989).

In addition to rapid growth and high survival on infertile, sandy sites species such as A. colei ms, A. cowleana and A. tumida

• fix atmospheric nitrogen and therefore improve soil fertility for other crops,
• lower windspeeds and reduce sand-blasting of adjacent crops,
• produce large quantities of wood which are excellent fuels and amenable to conversion into charcoal (CTFT1985),
• resist insect attack (including termites and locusts), and
• have low palatability to grazing livestock (including goats).

The seeds of many dry-zone Acacia species were traditional food items of Australian Aborigines. The nutritional status of dry seed of Australian Acacia species is excellent, being typically high in protein (17-25%), fat (4-16%) and carbohydrate (30-40%) (Brand & Cherikoff 1985). The majority of species have an impermeable seed coat and the seed can be stored indefinitely (> 10 years) without deterioration, and will not rot or germinate if wetted, i.e. they constitute an ideal human famine food reserve.

This paper focuses on those Acacia species which produce heavy and easily harvested seed crops from an early age and which have the greatest potential to provide human food in dry, tropical environments, especially those in Africa. Africa faces massive human and environmental problems over the next few decades. More than 100 million Africans are living in a semi-permanent state of starvation. Food production has failed to keep pace with the rapid population increase, and had declined by 12% even before the 1984/85 and 1987/88 famines (Harrison 1987). In many areas the diet of African children is chronically short of energy and protein.

The purpose of this paper is to summarise existing knowledge of Australia’s subtropical dry-zone Acacia species with human food potential in order to aid their future research and utilisation.

METHODOLOGY AND RESULTS

The main sources of information for this paper have been published and unpublished literature dealing with the species (see References) and my field observations of these species in their native habitats in northern Australia, and trial plantings in west Africa and India. Information from various unpublished sources including herbarium label data, unpublished research reports and observations of Australian and overseas researchers has been sought to supplement the meagre published literature for little-known and recently described or undescribed species.

For the purposes of this review, species considered to have human food potential were those which:

(i) produced moderate or heavy seed crops which could be readily harvested and processed into food; and which were

(ii) recorded as having been utilized for human food by Aborigines.

This review identifies 44 Acacia species, originating in Australia’s subtropical dry zone, which have human food potential. The characteristics of these species are summarized in Table 1. The more promising of these species are discussed in the following section. Temperate and subtropical dry-zone Acacia species whose seed is reported to have been utilized for food by Aborigines, but which have not been discussed in the text of the paper, are listed in Table 2.

DISCUSSION

Most promising species

Acacia colei ms

A. colei ms is a hexaploid taxon presently included under A. holosericea. Sterile plants of A. colei ms can be distinguished from diploid and tetra-ploid taxa also presently under A. holosericea on the basis of phyllode characters. Mature phyllodes are obovate and slightly asymmetrical, 10-19 cm long and 2-5.5 cm broad, with 2-3 prominent and basally confluent longitudinal nerves. Secondary venation is longitudinally reticulate producing a pattern of slightly elongated (≤ 3 times as long as wide) nerve islands. A more prominent, nearly straight, longitudinal secondary nerve runs for nearly the length of the phyllode between the major nerves. A dense, felt-like covering of appressed, short sericeous hairs over the entire phyllode surface gives the plant its characteristically silvery blue appearance. The strongly and openly curved pods of A. colei ms are easily distinguished from the straight or shallowly curved pods of A. cowleana and the tightly inter-woven, coiled (2-3 complete spirals per pod) pods of A. neurocarpa (dipl...

Índice

• Cover
• Title
• Copyright
• Contents
• About the cover
• Preface
• Acknowledgments
• A note on nomenclature of Acacia holosericea
• Summary of Workshop conclusions
• Invited Papers
• Recommendations of the Working Groups
• Appendices