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III. Role of Plant Introduction
E. M. HUTTON
(Panicum maximum), kikuyu (Pennisetum clandestinum), and Setaria
(Setaria sphacelata).The indigenous legumes were also studied in Kenya,
and valuable ecotypes of Glycine wightii (formerly G.juvanicu)(Bogdan,
1966a) and species of Dolichos and Vigna have been made available to
pasture scientists in other countries. Kenya workers have studied both
native and introduced pasture plants at the Grassland Research Station,
Kitale, since I95 1. The cultivated varieties of herbage plants resulting
from this work were described by Bogdan ( 1965).
The Kenyan example could well be emulated in the countries of Central
and South America, where there is a wealth of indigenous legumes waiting to be collected, classified, and assessed. Latin America is the source of
a few important grasses, notably in the genus Paspalum, but does not
possess as valuable a grass flora as Africa. Although Africa has an extensive range of native legumes, it has not as yet contributed as many
promising pasture legumes as Latin America. There is an awakening
interest in many tropical countries in introduction of tropical legumes and
grasses that have shown promise elsewhere. Most of them still show a
reluctance to investigate their own rich native flora for promising pasture
As pointed out by Hutton (1970), Australia is singularly deficient in
indigenous legumes and grasses that can be used as the basis for improved
pastures and increased animal production. As a result, there has been a
continuing interest in Australia in pasture plant introduction, which commenced on a random basis about the 1880’s and became organized in
1930 with the establishment of the Plant Introduction Section of the
C.S.I.R. Division of Plant Industry (McTaggart, 1942). Up to the present,
50,000 introductlons have been brought into Australia and 6 I % of these
are pasture and forage species. Much of the current pasture development
in the Australian Tropics is based on the chance annual introduction
Townsville stylo (Stylosanthes humilis) which was recognized at Townsville around 1900 and known formerly as Townsville lucerne. Introduction of tropical pasture species has been a major aim of C.S.I.R.O.
plant introduction work since its inception, and a large number of legume
and grass accessions from tropical countries have been evaluated over
the years. The selection of grasses adapted to northern Australia has been
relatively easy, whereas obtaining adapted legumes has proved difficult,
particularly for the subtropics, where rainfall is variable and frosts can
Since the turn of the century, the Australian wet tropics of about 4
million acres of northeastern coastal country between Mossman and Mackay has had adapted introductions of tropical grasses such as guinea,
molasses, and para (Brachiaria mutica). Schofield ( 1941) eventually
obtained successful legumes for this area including stylo (Stylosanthes
guyanensis), centro (Centrosema pubescens), puero (Pueraria phaseoloides), and calopo (Calopogonium mucunoides).
Much of the plant introduction work for northern Australia over the
last thirty years has aimed at obtaining legumes and grasses for pasture
development in the extensive tropical monsoonal and humid subtropical
areas between latitudes 30"sand 11"sand comprising about 260 million
acres (J. G. Davies and Eyles, 1965). Miles ( 1 949) made distinct progress
with this problem by evaluating an extensive range of introduced legumes
and grasses in central coastal Queensland from 1936 to 1946. He showed
that the low mineral and protein status of the native pastures could be
raised by perennial legumes in a number of genera including Arachis,
Centrosema, Desmodium, Glycine, Indigofera, and Stylosanthes. The
most promising grass introductions included ecotypes of Chloris gayana,
Cenchrus ciliaris, Digitaria sp., Panicum maximum, Paspalum notatum,
Setaria sphacelata, and Urochloa sp. Miles' results (1 949) stimulated
the first work in overseas plant exploration by Australia. Hartley (1949)
joined a U.S.D.A. expedition to subtropical South America and collected
mainly ecotypes of species in the genera Arachis, Desmodium, Stylosanthes, and Paspalum. From these introductions the cultivars Oxley
Fine-stem stylo and Hartley plicatulum (Paspalum plicatulum) (Bryan
and Shaw, 1964) have been selected.
Another ten important overseas collections of pasture plants have
been made by Australians in tropical monsoonal and humid subtropical
areas during the period 1952-1968 (Hutton, 1970). A range of material
was collected, particularly in the legume genera Centrosema, Desmodium,
Glycine, Phaseolus, and Stylosanthes, and the grass genera Cenchrus,
Panicum, Paspalum, Setaria, and Urochloa. Only the introductions from
J. F. Miles' visits to South Africa and east and west Africa in 1952 have
been fully evaluated. These have yielded Miles Lotononis (L. bainesii)
(Bryan, 1961), Rongai Dolichos lablab (W,ilsonand Murtagh, 1962), and
Samford Rhodes grass. R. J. Jones' collections ( 1 964) of Setaria sphacelata from East Africa have already produced the frost-tolerant cultivar Narok setaria, and it is anticipated that further promising lines will
come from these. The systematic exploration in 1965 of legumes and a
few of the grasses by Williams ( 1966) in the main states of Brazil, and in
Bolivia, Paraguay, and northern Argentina, has substantiated that these
areas are rich in indigenous species potentially valuable as tropical and
subtropical pasture plants. Williams found annual types of stylo similar to
Townsville stylo in a number of regions.
E. M. HUTTON
Due to the progress made on plant exploration and introduction for
the tropics, it is now more difficult to find native legumes and grasses
which are superior to existing pasture cultivars. This is no reason to curtail this activity, as only a fraction of the almost unlimited variation in the
indigenous flora of countries like South and Central America and Africa
has been investigated. With the advances in knowledge of the feeding
value of pastures relative to species and management, variants of present
cultivars or even new species could be required and may well be found
among the native plants of these and other countries. In any case, the
pasture plant breeder needs a continual flow of new genetic material
which can be obtained only through plant exploration and introduction.
Australian research centered in Queensland is now in the forefront
on the introduction, selection, and development of legumes for tropical
pastures. This has resulted from the realization that legume-based pasture
is the most economical method for the development of the cattle industry
in the vast unused coastal and subcoastal areas of northern Australia
(J. G. Davies and Eyles, 1965). Maintenance of around 40% of a phosphate-responsive legume in a tropical pasture is the cheapest way to
provide nitrogen for the pasture and grazing animal (Hutton, 1968b).
In this section the origin and agronomic features of the principal tropical legumes commercialized in Australia will be discussed. For their
detailed descriptions, see Barnard (1967). Some, like the drought-resistant Townsville stylo and siratro (Phaseolus utropurpureus), are
adapted to a wide range of conditions in northern Australia, whereas
those including centro, glycine, the desmodiums, and Miles lotononis, are
less drought tolerant and more restricted in their adaptation. With the
exception of Miles lotononis, aboveground growth of all the tropicals is
killed by frost, which is a constant feature of the subtropics in winter.
However, the perennial crown and root systems survive and regenerate
unless subjected to intense and repeated frosting. As larger areas of the
different tropical legumes are established, they will become hosts to
various diseases and pests which could affect persistence of some cultivars. Fortunately the main legumes do not appear to be affected by rootknot nematodes, and siratro is highly field resistant (Hutton and Beall,
1957). The root-damaging Amnemus weevil (Amnemus quadrituberculutus) is a serious pest of glycine and the desmodiums on the north
coast of New South Wales, whereas Miles lotononis and lucerne are re-
sistant and siratro is seldom attacked severely (Braithwaite, 1967; Mears,
1967). Other native weevils have damaged a number of the legumes in
north Queensland. The bean fly (Melanagromyzaphaseoli) can seriously
damage Murray lathyroides (Phaseolus lathyroides) throughout the
season but siratro, affected only in the seedling stage, can be protected
by seed treatment with dieldrin (R. J. Jones, 1965). The viruslike disease
“legume little leaf” due to a mycoplasma (Bowyer et al., 1969) affects a
number of the legumes and under relatively dry conditions markedly reduces stands of the desmodiums and Miles lotononis, and causes some
loss in siratro. In high rainfall areas, varying amounts of defoliation is
caused by Rhizoctonia solani in several legumes, particularly siratro.
Commercial seed production of the different legume cultivars is increasing in Australia and several other countries. In Kenya Desmodium
intortum, silverleaf desmodium ( D . uncinatum), Glycine wightii, Stylosanthes guyanensis, Dolichos lablab, and Trifolium semipilosum are
sold whereas in South Africa and Brazil G . wightii is the one usually
harvested for sale.
1. Townsville Stylo (S. humilis)
The history and potential of the annual Townsville stylo is summarized by Humphreys ( 1967), who noted that its natural spread is confined to the north of Western Australia, the Northern Territory, and
Queensland. It has thin, fibrous stems and narrow elongated and pointed
leaves, and forms a dense stand under favorable conditions. Flowers are
yellow and inconspicuous and arranged in a short compressed spike. The
brown pods are hooked, have two segments, but usually contain only
one true seed. The hooked pods cluster into small balls and comprise the
commercial seed, the yields of which range from 400 to 700 Ib per acre.
As a result of D. F. Cameron’s work (1965) with naturalized ecotypes,
three vigorous upright cultivars, Gordon (late), Lawson (midseason), and
Paterson (early black seeded) are being commercialized.
Townsville stylo (Fig. 1) is grown widely in Australia, particularly from
latitudes 1 1“ S to 24”sand where the annual rainfall is between 25 and 7 0
inches. It flourishes on poor sandy soils but does not establish readily on
deep cracking clays and in waterlogged areas. Seed is sown at 3-4 lb per
acre in conjunction with 1 cwt superphosphate per acre by aerial or
ground methods into grazed open woodlands or cleared and cultivated
areas. It is susceptible to shading from vigorous associate grasses, so it
E. M. HUTTON
FIG. I . Townsville stylo, Narayen Research Station, near Mundubbera, Queensland.
should be kept well grazed. Where there is strong grass competition, as in
the Northern Territory, Stocker and Sturtz ( 1 966) and H . P. Miller ( 1967)
obtained satisfactory establishment of Townsville stylo by sowing it
immediately after a burn early in the wet season which rapidly destroyed
growing native grasses. A fall of rain of an inch or more in early summer
will cause rapid germination of seed. The young seedlings are quite
drought resistant, but a prolonged dry period will cause their death. The
high actual seed yields of 800-1000 Ib of seed per acre and the high percentage of hard seed ensure the persistence of Townsville stylo.
Norman and Arndt ( 1959) in the Northern Territory and Shaw ( 196 1)
in central Queensland proved the value of Townsville stylo in beef production and so paved the way for its widespread use in northern Australia.
It is proving successful in the tropical monsoonal areas of Southeast
Asia, the Philippines, Brazil, Central America, and East Africa as well
as in southern Florida (Kretschmer, 1965).
2 . Schojeld Stylo (Stylosanthes guyanensis)
This perennial, which originates from Brazil (Schofield, 1941), is
naturalized in the wet Tropics of northeastern Australia. It is tall and
branched with hairy stems, narrow pointed leaflets, and compact spikes of
small yellow flowers. Seeding is profuse, and the small brown singleseeded pods shed on ripening, which makes mechanical harvesting
Schofield stylo grows in frost-free conditions in northern Australia
where annual rainfalls are 35-160 inches, summer temperatures are high,
and soils remain moist. It is sown at 2 Ib per acre, usually after cultivation, grows well on both poor and fertile soils, and is compatible with
tropical grasses like guinea and molasses. Heavy grazing and fire will
soon reduce stands of this legume.
A few recent introductions of S . guyanensis from central and South
America are superior to Schofield stylo, as they are prostrate and branch
vigorously from the base under heavy grazing. Various ecotypes of
perennial stylo are being increasingly grown in east Africa and will no
doubt be grown more widely in the Tropics.
3. Oxley Fine-Stem Stylo
This stylo came from Paraguay and was one of Hartley's collections
(1949). It was selected as a result of Shaw's work (1967a,b) on granitic
spear grass soils of southern Queensland. It is semiprostrate, well
E. M . HUTTON
branched, and has an underground crown. The leaflets are narrow and
pointed, and the small yellow flowers are in compact spikes. The brown
single-seeded pods fall very rapidly as they ripen, which makes harvesting particularly difficult.
Oxley fine-stem stylo is frost and drought tolerant and is adapted to the
ligher soils of Australia’s subtropics in annual rainfalls of 28-50 inches.
It is sown at 1-2 Ib per acre and is compatible with buffel and Rhodes
I . Siratro ( P . atropurpureus)
Siratro (Fig. 2) is a perennial bred from two Mexican ecotypes of P.
atropurpureus (Hutton, 1962). I t has deeply penetrating swollen roots
and a high level of drought resistance. If the soil is moist for an extended
FIG.2. Siratro growing at Sarnford Pasture Research Station, near Brisbane, Queensland.
period, the trailing pubescent stems root at random along their length. Its
twining habit allows it to reach the light in dense pastures. Leaves have
three ovate leaflets with dense silvery hairs on the lower surface. The
evidence indicates that siratro is a short-day plant with abundant flowering and seeding occurring when vegetative growth is checked by dry
weather or cooler conditions in autumn. The relatively large flowers are
in a raceme and are deep red, and age to dark purple before withering. The
pods are narrow and cylindrical and they shatter as they ripen from the
raceme base. Actual seed yields are around 800 Ib per acre under favorable conditions but commercial yields are 100- 150 Ib per acre because of
shattering. Seed is usually scarified to reduce the percentage of hard seed.
Siratro grows from latitude 1 1 "S to 30"s in Australia in annual rainfalls
from 25 to 70 inches and thrives on a variety of soils, particularly those
well drained. Seed is sown at 2-3 Ib per acre on well grazed native grassland or cultivated areas, and establishment is rapid under favorable
conditions. It is compatible with a range of grasses including Rhodes,
buffel, green panic (Panicum maximum var. trichoglume), guinea, and
Nandi setaria and its growth is rapid at the height of the wet season.
Siratro, due to its perenniality, high actual seed yield, and quick regeneration from seed, is usually quite persistent provided year round
stocking rates are kept within reasonable limits of a cattle beast to
Siratro is promising in tropical monsoonal areas in the countries of
Central and South America and eastern Africa. In eastern Africa its
growth is restricted at elevations above sea level of 4500 feet or more.
Good growth of siratro is also reported from New Guinea, Fiji, Philippines, Rajasthan (Patil et al., 1967), southern Florida (Kretschmer,
1966), and Southeast Asia.
2 . Murray lathyroides ( P . lathyroides)
Murray lathyroides was first reported in the Brisbane district toward
the end of the last century (Bailey and Tennison-Woods, 1879) and is
now naturalized along the coast of northeastern Australia. Ecotypes of
P . futhyroides are widely distributed and grow wild in a number of countries of Southeast Asia, Central and South America, and Africa and also
in New Guinea, the Pacific and Hawaiian Islands, southern Florida, West
Indies, Philippines, and India. They vary from upright to prostrate and
have either sparse or strong basal branching. Murray lathyroides is an
erect vigorous annual or biennial with some branching and smooth
lanceolate leaflets. The conspicuous deep pink to red flowers are in a
raceme, and the narrow cylindrical pods shatter as they ripen from the
Murray lathyroides was developed by Paltridge ( 1942) because of its
vigor, palatability, and high protein content. It grows well in pasture
mixtures, on a range of soils in annual rainfalls of greater than 30 inches
and is seeded into cultivated land at 2-3 Ib per acre. Periodic cultivation
is necessary to ensure its regeneration from fallen seed. An important
attribute is its ability to persist on heavy-textured waterlogged soils.
The role of the desmodiums as pasture plants has been summarized by
Bryan (1966, 1969). Greenleaf (D.intorturn) and silverleaf ( D . uncinaturn) are the two commercialized in Australia. A number of D. canurn
and D . sandwicense ecotypes have been introduced, but none have shown
real promise as yet, although kaimi Spanish clover (D. canurn) has
proved of value in Hawaii (Hosaka, 1945; Younge et al., 1964). D .
gyruides, a shrub used to prepare land for cocoa in Fiji and elsewhere,
has potential for forage as it persists under grazing and produces green
leaf in the dry season in frost-free areas. The strongly stoloniferous D.
heterophyllurn, naturalized in a number of tropical countries, has performed well in association with aggressive grasses like pangola in the wet
Tropics of north Queensland.
1 . Greenleaf (D.intorturn)
Indigenous ecotypes of D. intorturn are common in Central America
and Brazil (Williams, 1966), and greenleaf is a mixture of three similar
introductions from El Salvador and Guatemala. It is rather a coarse trailing perennial which roots along the pubescent stems under moist conditions and has a fibrous root system (Fig. 3). The deep green, rounded
leaflets often have a reddish brown to purple flecking on the upper surface. Short days induce flowering and the small deep lilac to pink flowers
are in compact terminal and axillary racemes. The small narrow and recurved seed pods are segmented and have hooked hairs that cause them
to adhere to clothing and animals. Seed yields of 100-120 Ib per acre are
being obtained under irrigation in the dry season.
Greenleaf thrives on a variety of soils in the coastal areas of northern
Australia where annual rainfall is 40 inches or more and the dry season
not too severe, as in the Northern Territory. It is not particularly drought
resistant and grows well in moist elevated areas as the Atherton Table-
FIG. 3. Greenleaf desmodium, Samford Pasture Research Station, near Brisbane,
land of north Queensland. It is sown at 2 Ib per acre in pasture mixtures
into cultivated land, and establishment is often slow because of retarded
E. M. HUTTON
nodulation. Once established, it grows rapidly under warm moist conditions and is compatible with most of the tropical grasses. Leaves and
shoots are quite palatable to cattle (Bryan, 1966), and it thins out at
stocking rates in excess of a beast to the acre.
Types of D . intorturn similar to greenleaf have performed well in trials
in Tanzania and Uganda (Naveh and Anderson, 1967; Stobbs, 1969a)
and a number of other tropical countries. Near the equator it grows from
sea level to elevations of 6500 feet, so is very adaptable.
2. Silverleaf ( D . uncinatum)
Silverleaf desmodium was introduced from Brazil in 1944, and more
recently Williams (1966) collected similar ecotypes from there. It is a
trailing perennial with thin, ovate, hairy leaflets which have a broad
irregular silver band along the midrib. Moistness induces rooting along the
pubescent stems, and swollen as well as fibrous roots are produced.
Flowering occurs in short days, and the paired lilac to mauve flowers are
borne in open terminal and axillary racemes. The segmented sickleshaped pods have hooked hairs, and the seeds are flat and larger than
those of greenleaf. Commercial seed yields of 200-300 Ib per acre are
Silverleaf is not as hardy as greenleaf and thrives only in moist coastal
areas of northeastern Australia where annual rainfall is 40 inches or more.
Growth is restricted by high summer temperatures so elevated areas with
cooler nights often provide it with a better environment. It grows on a
variety of soils and is sown in mixtures at 2 lb per acre on cultivated
land. Establishment is usually rapid and it combines well with grasses
like the setarias, panicums, and paspalums. Palatability of leaves and
shoots is high (Bryan, 1966), and it is susceptible to overgrazing.
Silverleaf desmodium has proved promising in several countries,
notably in East Africa (Bogdan, 1965; Naveh and Anderson, 1967).
More recent results have indicated that it will be replaced there by greenleaf or a similar type of D.intorturn. It is of interest that at Palmerston
North, New Zealand, silverleaf was the only tropical legume surviving in
the third season from a range which was sown.
( G . wightii)
The perennial G . wightii is mainly indigenous to Africa, although there
are some Southeast Asian forms. Descriptions are given by Verboom
( 1965) of the five main types in Zambia and by Bogdan ( 1966a) of the five
distinct African types he assembled in his plots at Kitale in Kenya.