Macroptilium lathyroides (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Macroptilium lathyroides (L.) Urban

Protologue: Symb. Antill. 9: 457 (1928).

Family: Leguminosae

Chromosome number: 2n= 22

Synonyms

Phaseolus lathyroides L. (1763).

Vernacular names

• Phasey bean (En). Wild pea bean (Am)
• Indonesia: kacang batang
• Thailand: thua-phi.

Origin and geographic distribution

Phasey bean originated in tropical America and is now widely distributed, although usually of only minor importance, throughout Central and South America, the Caribbean, Australia, South-East Asia and parts of Africa.

Uses

Phasey bean is primarily used as a forage plant, but can be used as a cover crop in rotations and as green manure.

Properties

Nitrogen concentrations range from 4% in young vegetative growth to 1% when most leaves have fallen off and the sample is primarily old green stem. Similarly, digestibility can range from 70-40%. There are 110-120 seeds/g.

Botany

Herbaceous annual or less commonly short-lived perennial, erect with variable branching, 0.5-1.5 m tall, with base of stem becoming somewhat woody, sometimes becoming trailing or twining, especially under shade. Stems terete, with long deciduous reflexed hairs. Leaves trifoliolate; leaflets ovate-lanceolate to elliptical, 3-8 cm × 1-3.5 cm, not lobed. Inflorescence a semi-erect or erect raceme up to 15 cm long, borne on peduncle up to 40 cm long; pedicels very short; flowers red-purple, about 1.5 cm long. Pod subcylindrical, 5-10 cm × 3 mm, containing 18-30 seeds, abruptly dehiscent. Seeds oblongoid to rhomboidal, 3 mm long, mottled light and dark grey-brown.

Sometimes a subdivision of the species into two varieties is made:

• var. lathyroides : leaflets narrowly lanceolate, often more or less lobed; only in tropical America;

• var. semierectum (L.) Urban (synonym Phaseolus semierectus L.): leaflets ovate to elliptical, not lobed; this variety is the widely distributed forage plant.

Phasey bean is day-neutral for flowering and can flower throughout the wet season but under shaded and humid conditions flowering and seed production are depressed and the plant assumes a twining growth habit. There is evidence that twining is initiated by shading whereas flowering is depressed by high humidity, even though these environmental factors often occur together in the field. It is strictly self pollinated. The only cultivar is "Murray", developed in Australia, which is taller and more robust than most of the lines evaluated.

Ecology

Phasey bean is adapted to a wide rainfall range of 500-3000 mm. The optimum day/night temperature for growth is 35/20 °C. Plants are killed by frost but usually seed before frosting. It is adapted to acid and alkaline soils, and a wide range of soil textures from sand (given reliable rainfall) to heavy clay. It is tolerant of waterlogging and poor drainage and frequently grows in drains along the edges of roads. Drought survival is achieved by soil seed reserves.

Agronomy

Phasey bean is easy to establish from seed and seeding rates of 3-10 kg/ha are recommended. Establishment in undisturbed soil, particularly in existing pasture, is rarely successful, except under favourable moisture conditions with scarified seed. In subtropical regions, it can be sown during spring and summer when moisture conditions are favourable. Seedlings nodulate freely with native cowpea rhizobia, and seedling growth is vigorous when sown into a prepared seed-bed.

Seedlings are susceptible to attack from bean fly (Melanagromyza phaseoli) and plants are susceptible to Phaseolus virus 2, root-knot nematode (Meloidogyne javanica), especially on sandy soils, and to mildew.

It can be cut or grazed, but does not tolerate sustained heavy cutting or grazing which can greatly reduce or even eliminate seeding. If grazing animals have scope for selection, they may avoid grazing phasey bean till after seeding.

DM yields of 13 t/ha at 90 days after sowing have been reported. Although phasey bean seeds readily, seedling recruitment is usually poor and so persistence is poor in permanent pastures after the second year. Recruitment can be aided by rough cultivation. Hence its main use is as a component of a mixture to give grazing in the first year but it also shows some promise as a one year legume ley or as a forage intercrop. Plants are killed by fire, but stands can recover through seedling germination after fire. Good hay can be made if loss of leaves is avoided. Harvested seed yields are typically 200-250 kg/ha but much seed is lost through dehiscence and the true seed yields would be higher.

Genetic resources and breeding

There are no breeding programmes on phasey bean. Germplasm collections are held by ATFGRC (CSIRO, Australia) and CIAT (Colombia). There is known variation for mildew resistance and in the intensity of branching.

Prospects

It is likely that the potential for phasey bean lies in its use in short leys and as an intercrop, or to provide first-year feed when sown as part of a mixture for permanent pastures. Further exploitation of the variability within this species may make it more suited to these roles.

Literature

• Cameron, D.G., 1985. Tropical and subtropical pasture legumes 8: Phasey bean (Macroptilium lathyroides). The predecessor of Siratro. Queensland Agricultural Journal 111: 211-214.
• Elich, T.W., 1988. Studies on seed production in phasey bean (Macroptilium lathyroides). CSIRO, Australia, Division of Tropical Crops and Pastures, Technical Memorandum No 58. 9 pp.
• Oram, R.N., 1990. Register of Australian herbage plant cultivars. CSIRO, Australia. p. 240.
• Paltridge, T.B., 1955. Sown pastures for southeast Queensland. CSIRO, Australia, Bulletin No 274. pp. 106-107.
• Skerman, P.J., Cameron, D.G. & Riveros, F., 1988. Tropical forage legumes. FAO, Rome. pp. 337-345.
• Thro, A.M. & Shock, C.C., 1987. Performance of subtropical forage legumes in Louisiana, south-central United States. Tropical Agriculture 64: 297-304.

Authors

R.M. Jones & L. 't Mannetje