Stylosanthes capitata Vog.

Leguminosae

Description

An erect, ascendent to decumbent, much-branched perennial. Stems to 1 m high, woody toward the base, with short, dense, white hairs and some scattered bristles, the pubescence generally more dense below each node. Leaflets oblong to elliptic, to 30 mm long and 15 mm wide but usually less, densely villous on both surfaces, seven to nine pairs of conspicuous veins. Petioles 3 to 6 mm long, densely villous. Rachis 1.0 to 3.5 mm long. Sheath of stipules 7 to 9 mm long, densely villous, longer than the subulate teeth, several nerved. Inflorescence a thick spike, capituliform, about two thirds as wide as high, to 35 mm long, many flowered, on peduncles usually 5 to 7 cm long. Bracts with a single, very reduced leaflet. Sheath often purplish, 8 to 12 mm wide, conspicuously 11 to 17 nerved, copiously softly pubescent. Axis rudiment 5 to 7 mm long in fruit, very long ciliate. Outer bracteoles 1 to 3 mm long, ciliate. Inner bracteoles two, 2.0 to 2.5 mm long, much narrower than the outer, lobes mostly acute and sparsely ciliate, about 2.5 mm long. Standard obovate, 5 to 7 mm long. Wings obovate, 4 to 5 mm long, auriculate at the base. Keel petals 3 to 4 mm long, falcate and auriculate. Loment to 2.5 mm broad, reticulate nerved. Both articulations usually fertile but either can sometimes be abortive, upper about 3.5 mm long and glabrous, lower somewhat shorter and glabrous or sparsely pubescent. Beak uncinate, about 1 mm long, glabrous or with a few short stiff hairs on the inner face (Mohlenbrock, 1957).

Native in a discontinuous pattern from south-eastern Brazil to Venezuela. Restricted in distribution compared with S. humilis and S. guianensis. CIAT collections range from 22°S in Brazil to 10°N in Venezuela (Grof, Schultze-Kraft and Muller, 1979), and from lowlands to 1 000 m in elevation. 

Grows from semi-arid tropical areas in Bahia, Brazil, to the subtropical conditions of Mato Grosso and Minas Gerais, Brazil, to the humid tropical coast of Pernambuco, Brazil. Rainfall range is from 500 to more than 1 500 mm annually.

Often found in treeless and open woodland savanna habitats. It thrives in the extremely acid (pH 4.5), infertile, sandy Cerrado soils, often in association with S. scabra, but is absent from the savannas on the western side of South America. On soils of medium acidity (pH 5.5 to 6.5), it fails to nodulate and dies.

Some accessions are extremely heavy seeders, producing yields of up to 1 000 kg./ha.

There is wide variability and many natural ecotypes. One cultivar, Capica, a mixture of five accessions, CIAT 1315, 1342, 1693, 1728 and 1943, has recently been released by CIAT in Colombia. It is hoped that its wide base will give it wide adaptation and some anthracnose control (Edye, Grof and Walker, 1984).

A very variable species in many morphological characters, including size and shape of the inflorescence, habit of growth, hairiness of the stems and leaves, and colour of the stems.
Its adaptation to the low phosphate, acid, sandy soils of the Cerrado give it considerable promise in South America. Because of its many similarities to S. scabra, it could also have considerable value in Australia, especially in view of its high levels of anthracnose resistance. It appears well suited to low-input, extensive grazing systems. To date, it has not received the attention it deserves in Australia because of Rhizobium difficulties.
A prolific seed producer, with a high level of hard seed in inflorescences that are readily grazed over the dry season, S. capitata can thus be spread widely by livestock. It also regenerates readily from seed.

Highly specific.

Grof, Schultze-Kraft and Muller (1979); Edye, Grof and Walker (1984).

Variation in reaction to anthracnose is present, with some lines resistant to a wide range of races, and to stem borers and budworms (Lenne and Calderon, 1984).

Self-pollinates readily in isolation, but outcrossing of up to 20 percent has been recorded in mixed populations (Miles, 1983).