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III. Role of Plant Introduction

III. Role of Plant Introduction

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6



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

plants.

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

occur.

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,



TROPICAL PASTURES



7



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



8



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.

IV.



Tropical Legumes



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-



TROPICAL PASTURES



9



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.

A. STYLOS

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



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E. M. HUTTON



FIG. I . Townsville stylo, Narayen Research Station, near Mundubbera, Queensland.



TROPICAL PASTURES



11



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

difficult.

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



12



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

grasses.



B. PHASEOLUS

SPECIES

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.



TROPICAL PASTURES



13



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

1.3-3.0 acres.

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



14



E.



M.



HUTTON



lanceolate leaflets. The conspicuous deep pink to red flowers are in a

raceme, and the narrow cylindrical pods shatter as they ripen from the

raceme base.

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.



C. THEDESMODIUMS

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-



TROPICAL PASTURES



FIG. 3. Greenleaf desmodium, Samford Pasture Research Station, near Brisbane,

Queensland.



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



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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

obtained.

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.

D. GLYCINE

( 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.



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