Indigofera spicata


Scientific name

Indigofera spicata Forssk

Synonyms

Indgofera endecaphylla sensu auct.
Indgofera hendecaphylla sensu auct.
Indgofera parkeri Baker
Indigofera pusilla Lam.
Indgofera spicata sensu auct.
Indigofera compressa sensu auct.
Indigofera endecaphylla sensu auct. div.

Note: There is considerable confusion in the literature between Indigofera spicata Forssk. and Indigofera hendecaphylla Jacq., which were initially considered synonyms, but are now treated as separate species.  This leads to difficulties in ascribing effects attributed to Indigofera spicata in older literature, particularly in relation to toxicity, to one species or the other.

Family/tribe

Fabaceae (alt. Leguminosae) subfamily: Faboideae tribe: Indigofereae. Also placed in: Papilionaceae

Common names

English: creeping indigo, lawn indigo, trailing indigo
Madagascar: anky, famafatsambo
Portuguese: amendoim-bravo (Brazil)

Morphological description

Prostrate to weakly ascending, spreading, perennial herb, to 0.5 m high, and 1 m across, with strong, deep, woody taproot and low to submerged crown; young stems ridged (flattened when young), green or yellowish, strigose with sparse, hyaline to white appressed, equally biramous hairs; older stems brown, sometimes rooting at the nodes.  Leaves pinnate, (4 -) 5 - 7 leaflets, 12 - 40 mm long; stipules triangular (2.5 - ) 3.5 - 5.5( -6.5) mm long, with scarious margins, glabrescent, not spinescent, persistent; petiole 2 - 6 mm long; rachis furrowed.  Leaflets alternate; stipellae absent or inconspicuous, 0.2 - 1.2 mm long, membranous, some dividing into 2 or 3 segments; leaflets obovate, (3-) 4 - 11( -16) mm long, 2.5-8(-10) mm wide; upper surface dull green, glabrous or with sparse, appressed hairs; lower surface green with sparse to moderately dense, appressed hairs; apex obtuse (with short mucro); veins not prominent.  Inflorescences 30 - 65( - 80) mm long; peduncle 15 - 20 (- 25) mm long; bracts triangular (margin scarious), 1.2 - 2 mm long; flowers pink to orange-red, sometimes white; pedicel 0.3 - 0.7 mm long.  Calyx 2 - 3 mm long; lobes sub-equal, longer than the length of the tube and covered with sparse to moderately dense, white, appressed hairs.  Standard reddish, sometimes white, obovate, 3.8 - 4.9 mm long, 2.5 - 3.7 mm wide; hairs sparse (few at apex only), hyaline to white; apex obtuse.  Wing oblong to spathulate, 3.7-4.5 mm long, 0.5 - 1.1 mm wide.  Keel 3.9 - 4.4 mm long, 1 - 1.3 mm deep; lateral pockets 0.3 - 0.5 mm long; apex acute; glabrous or with sparse, hyaline hairs at the tip.  Staminal tube 2.3 - 3.2 mm long, colourless.  Ovary moderately to densely hairy.  Pod descending, terete (often torulose when young), 10 - 18 mm long, 1.5 - 2 mm wide, yellowish and brown, strigose to glabrescent; hairs sparse, appressed; apex shortly pointed (to 0.5 mm long); endocarp not spotted; seeds cuboid, 4 - 8 per fruit, 1.3 - 1.6 mm long, 1 - 1.4 mm wide; 480,000 - 830,000 seeds/kg, depending on provenance.

Distinguishing features:

I. spicata: Pod 10 - 18 mm long with a short, blunt tip 0.5 mm long; inflorescence to 80 mm long; leaflets 5 - 7, obovate; staminal tube 2.3 - 3.2 mm long.

I. hendecaphylla: Pod 22 - 27 mm long (including a distinct beak 1.5 - 2.5 mm long); inflorescence over 120 mm long; leaflets 7 - 10, obovate to elliptical; staminal tube 3.5 - 4.0 mm long.

Distribution

Native to:
Africa: Burkina Faso, Burundi, Cameroon, Central African Republic, Democratic Republic of the Congo, Ethiopia, Kenya, Malawi, Mozambique, Rwanda, South Africa (N), Sudan, Tanzania, Uganda, Zambia, Zimbabwe.

Indian Ocean: Madagascar, Mauritius.

Arabian Peninsula: Yemen (S).

The endemic range of I. spicata is much more restricted than that of I. hendecaphylla.  Since it is not possible to individualise some of the reported characteristics for the two species, much of the information here will relate to the Indigofera spicata-hendecaphylla complex.

Naturalised:
Widely naturalised in other parts of the tropics and subtropics.
Found in open disturbed areas. 

Uses/applications

Mainly planted for cover, green manure and erosion control in coffee, tea and rubber plantations in the tropics and subtropics.  It occurs in natural pasture, but has not been sown as forage to any extent.  Minor source of indigo dye.

Ecology

Soil requirements

Best adapted to dark clay and clay loam soils of pH 5.0 - 7.7, but also found on sandy soils, and soils with pH as low as 4.0 and as high as 8.5.  Tolerant of low soil P status.

Moisture

Top

Mostly found in areas with average annual rainfall of 600 - 1,500 mm, but up to 4,000 mm.  Annual rainfall in collection areas in Yemen is as low as 200 mm, although these were edges of drainage lines.  I. spicata appears to extend the distribution of the complex into lower rainfall areas, but is still found in higher rainfall areas.

Temperature

While primarily a warm season species complex, it is widely adapted, being found in areas of the lowland tropics and subtropics, and upland tropics (to 2,800 m ASL at Quito in Ecuador).  24 hour average annual temperatures range from 13 - 27 C.

Light

Performs best in full light, but tolerates light shade.

Reproductive development

I. spicata commences flowering in late summer/early autumn and fruiting in early/mid-autumn.

Defoliation

Extremely tolerant of regular low defoliation, becoming a weed in turf.

Fire

Top

No information, but probably tolerant of fire by virtue of the very low or submerged crown.

Agronomy

Establishment

I. spicata often has high levels of hard seed, but these can be broken down with mechanical or hot water scarification.  Care should be taken with some hot water treatments that can also kill previously germinable seed.  I. spicata will in most cases nodulate effectively on native rhizobia, but seed can be inoculated with Bradyrhizobium strains such as 210407 (Japan) or CB 756 (Australia).  Being a small seed, it should be sown no deeper than about 1 cm.

Fertiliser

In the absence of empirical information, it is probably appropriate to treat I. spicata like other moderate fertility legume species such as Macroptilium atropurpureum .  On soils with less than about 8 ppm available phosphorus, 20 - 30 kg/ha elemental P may be required at establishment, and 10 - 20 kg /ha/yr P for maintenance.  The need for other nutrients, particularly K and S, should be monitored by soil analysis or foliar deficiency symptoms.  Molybdenum may be required at 100 g/ha elemental Mo at establishment on deficient soils, and 100 g/ha Mo every 4 - 5 years as maintenance, particularly on more acid soils.

Compatibility (with other species)

Commonly found in association with lower growing and sward -forming grasses and legumes.

Companion species

Top

Pests and diseases

Very few pests and diseases of any consequence.  Okra mosaic virus (OMV, tymovirus group) has been isolated from Indigofera spicata in Nigeria.

Ability to spread

Spreads readily due to prolific seed production, and ready establishment in disturbed situations, including heavily defoliated swards.

Weed potential

Most references to weed threat relate to toxicity (see below).  It is rarely a weed in crops, but is a common weed of turf in some regions.

Feeding value

Nutritive value

Top

Analyses of material from lines listed as I. spicata, but probably predominantly I. hendecaphylla, show crude protein levels as high as 23% and neutral detergent fibre values as low as 32%.

Palatability/acceptability

I. spicata and I. hendecaphylla are palatable to livestock.

Toxicity

Much of the available literature states that leaves and more so seeds of I. spicata contain the amino acid, indospicine, which causes abortion in cattle, liver damage in sheep, cows and rabbits, and death in chickens.  Because of the taxonomic confusion, at least some of this will relate to I. hendecaphylla.  The toxic amino acid, indospicine, was originally isolated from I. spicata at a time before I. spicata and I. hendecaphylla were regarded as two separate species.  Literature review yields no reliable information on the relative indospicine content of the two individual species.
In view of the fact that a quite different Australian species (I. linnaei) contains indospicine at toxic concentrations, and that recent chemical analysis of I. spicata collected from S.E. Queensland has determined that higher levels of indospicine are present in this species, all Indigofera species should be regarded as containing this toxin until proven otherwise.
In Australia, horses develop serious neurological disease after eating I. linnaei and I. spicata.  Ongoing unpublished studies have confirmed that cattle, a goat; camels and horses that have been exposed to indospicine in their diet accumulate the toxin in their muscle and other tissues, and dogs that have been fed meat from affected horses have died of liver disease, and this disease has been reproduced by feeding pure indospicine.  Dogs are much more susceptible to the liver damaging effects of indospicine than are other species, but this susceptibility varies widely within the species.
After experimental feeding of I. linnaei and I. spicata to ruminants, indospicine persists in the blood and tissues for some weeks after cessation of feeding, thus acting as a toxic residue.  Without more decay studies, recommendations as to withholding periods for meat livestock cannot at this time be given.

Production potential

Dry matter

I. hendecaphylla has produced yields up to 5 t/ha green matter after 2 months and 25 t/ha after 6 months.

Animal production

Top

No information

Genetics/breeding

2n = 16, 32.  Again there is confusion on the basis of true species identity.

Seed production

No information.

Herbicide effects

Susceptible to dicamba-MCPA mixtures.

Strengths

  • drought tolerant
  • nitrogen-fixing legume
  • adapted to wide range of soil types and conditions
  • tolerant of heavy grazing

Limitations

Top

  • toxicity
  • paucity of information

Other comments

Indigofera spicata has been largely avoided in pasture legume evaluation programs because of the toxicity issue.  While it is clear that both species contain or are even dominated by toxic provenances, there is sufficient agronomic merit in the complex to warrant more definitive study to select for low indospicine varieties in this potentially valuable forage legume
Rusa deer in Mauritius graze native I. spicata-dominant pastures at certain times of year, with apparently no ill effect.

Selected references

Aylward, J.H., Court, R.D., Haydock, K.P., Strickland, R.W. and Hegarty, M.P. (1987) Indigofera species with agronomic potential in the tropics. Rat toxicity studies. Australian Journal of Agricultural Research, 38, 177 - 186.

Christie, G. S., Wilson, M., and Hegarty, M. P. (1975) Effects on the liver in the rat of ingestion of Indigofera spicata, a legume containing an inhibitor of arginine metabolism. The Journal of Pathology, 117, 195 - 205

Du Puy, D.J , Labat,J.-N. and Scrire,B.D., (1993) The separation of two previously confused species in the Indigofera spicata complex (Leguminosae: Papilionoideae) Kew Bulletin 48, 727 - 733.

Hegarty, M.P., Kelly, W.R., McEwan, D., Williams, O.J. and Cameron, R., (1988). Hepatotoxicity to Dogs of Horse Meat Contaminated with Indospicine.  Aust. Vet. J. 65, 337-340.

Hegarty, M. P. and Pound, A. W. (1968) Indospicine, a new hepatotoxic amino-acid from Indigofera spicata. Nature 217, 354 - 355.

Hutton, E.M. and Guerassimoff, J. (1966) Problems in breeding the legume Indigofera spicata for tropical pastures. Euphytica, 15, 353 - 361.

Hutton, E.M. (1960). Flowering and pollination in Indigofera spicata, Phaseolus lathyroides, Desmodium uncinatum and some other tropical legumes. Empire Journal of Experimental Agriculture 28, 235 - 43.

Kelly, W.R., Young, M.P. Hegarty, M.P. & Simpson, G.D. (1992) The hepatotoxicity of indospicine in dogs. In James, L.F., Keeler, R.F., Bailey Jr, E.M., Cheeke & P.R., Hegarty, M.P., eds, Poisonous plants, Proceedings of the 3rd International Symposium, 126-130.  Ames, Iowa State Univ Press.

Strickland, R.W., Lambourne, L.J. and Ratcliff, D (1986) The palatability, feeding value and apparent toxicity of 150 legume species fed to rats.  Genetic Resources Communication Number 10. CSIRO, Division of Tropical Crops and Pastures, St Lucia, Brisbane, Qld, Australia. ISBN 0643-03683 0.

Strickland, R.W., Lambourne, L.J. and Ratcliff, D (1987) A rat bioassay for screening tropical legume forages and seeds for palatability and toxicity. Australian Journal of Experimental Agriculture 27, 45 - 53.

Sunarno, B. (1997) Indigofera hendecaphylla Jacq., In Faridah Hanum, I. and Maesen, L. J. G. van der (eds), Plant Resources of South-East Asia No 11. Auxiliary plants.  pp 156 - 158 (Backhuys Publishers, Leiden, The Netherlands).

Wilson, P.G. and Rowe, R. (2008) A revision of the Indigofereae (Fabaceae) in Australia. 2. Indigofera species with trifoliolate and alternately pinnate leaves. Telopea, 12, 293-307.

Internet links

Cultivars

Cultivars

Country/date released

Details

Nil          

Promising accessions

Top

Promising accessions

Country

Details

Nil