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X. Breeding and Genetics of the Main Legumes
E. M. HUTTON
ums (Rotar et al., 1967) to cross-pollination in lucerne, white clover, and
some of the African trifoliums including T. semipilosum (Pritchard and
't Mannetje, 1967). In the self-pollinating tropicals a high relative humidity is needed for pollen-tube growth on the stigmas, and seeds are set only
if the humidity is adjusted to the optimum level around the emasculated
and hand-pollinated flowers. In leucaena the round heads of small flowers
are self-pollinated but can be emasculated after anthesis by washing in a
very weak solution of a nontoxic wetting agent and then hand-pollinated.
D. F. Cameron (1965) found that significant variation occurred in
flowering time, growth habit, plant growth, and seed yields among a large
number of collections made from the naturalized populations in Queensland and the Northern Territory. There was a continuous range in flowering time from early to late, and plant growth was related to time of flowering. Late types gave higher dry matter yields than midseason types, which
gave higher yields than early types. The midseason types gave the highest
Time of flowering and seed setting are very important in Townsville
stylo to ensure production of large amounts of seed for reestablishment
in the following wet season. D. F. Cameron (1967~)related flowering
time of 58 ecotypes with their collection site characteristics. In general
the late-flowering types were collected from areas with an annual rainfall
over 45 inches, and early types came from drier areas with a rainfall of
23-35 inches. Distribution was also correlated with latitude. The five
collections obtained south from Rockhampton were early or midseason
and all collections from the northern parts of Cape York Peninsula, the
Northern Territory, and Western Australia were late flowering. Late
types usually give higher yields than early types in areas with a long growing season, because they continue vegetative growth after early types
have set seed and stopped growing. With a short growing season, late
types are unable to flower and seed and fail to produce a dense sward in
the following season whereas early types regenerate well because they
flower and set seed before soil moisture is exhausted. Erect types usually
give higher yields than prostrate, particularly when associate grasses are
present in the pasture.
Inheritance of flowering time has been studied (D. F. Cameron, 1968)
in a diallel cross between nine lines ranging from early to late. In all
crosses involving two late-flowering types, late flowering was strongly
dominant and the 3 : 1 segregation indicated a major single gene difference
between these and other maturity types. A few hybrid populations contained some very early segregates indicating the presence of a recessive
gene at another flowering locus. A three-locus model involving genes
governing late, midseason, and early maturities was proposed.
Stylosanthes species comprise a polyploid series ( x = 10). S. humilis,
S . guyanensis, and S . hamata are diploids, S . mucronata is a tetraploid
and S . erecta a hexaploid, and all are perennials except S . humilis ( D . F.
Cameron, 1967d). Sterile hybrids resulted from the crosses S . humilis
x S . guyanensis and S . humilis X S . hamata, but fertile tetraploids were
induced by colchicine (D. F. Cameron, 1968). Of these the S . humilis
X S . guyanensis (cv. Schofield) progeny was the most perennial.
This cultivar was bred from two Mexican ecotypes of P. atropurpureus
and combines the stoloniferous habit of one with the higher yield and
better seeding ability of the other (Hutton, 1962). The aims of breeding
work with siratro (Hutton, 1965) are greater yield, persistence, and stoloniferous development, a longer period of active growth, higher seed yield,
and slower shattering pods. Two main cycles of crossing and selection
have been completed. The first produced higher-yielding and more stoloniferous lines than siratro. The second has recently given lines with higher
yield of dry matter and seed, and a longer period of active growth due to
ability to grow at temperatures of 50-70°F. Stoloniferous development
is not as pronounced in the latest lines, but this may not be disadvantageous, as under drier conditions this character is rarely expressed. A high
level of root-knot nematode resistance is being retained, and improvement
in tolerance to Rhizoctonia solani and “legume little leaf’ is sought.
Crosses were made between greenleaf and silverleaf desmodiums and
between greenleaf and D . sandwicense with the objective of introducing
valuable genes into greenleaf and generating new variation (Hutton and
Gray, 1967). Progeny from the first cross had a high degree of sterility
(95.7%) and progeny from the second cross were fully fertile. Both progenies gave promising segregates. No useful lines resulted from the cross
D . sandwicense x silverleaf.
Park and Rotar ( I968a,b) studied inheritance of flower and stem color,
leaflet markings, and petal anthocyanin concentration in Spanish clover
( D . sandwicense). Flower and internode color were each controlled by a
single gene, and these genes were linked. Silver midrib markings on the
E. M. HUTTON
leaflet and differences in anthocyanin concentration of petals also appeared to be under monogenic control.
McWhirter (1 968) established the occurrence in Desmodium of a
system of determination of the male-sterile, fertility-restored phenotypes
similar to cytoplasmic male sterility systems found in other angiosperms.
A scheme was presented utilizing genetic stocks for commercial production of F1 seed of the interspecific hybrid D . sandwicense X D . intorturn.
As a basis for glycine improvement variation of important characters
in a range of accessions was studied by Edye and Kiers ( 1966), and inheritance of some of these characters was determined by Wutoh et al. (1968b,
c) in selected crosses. The introductions varied in maturity from very
early to late, and in seed set and yield, stolon development, and frost
resistance. In a diallel cross of five glycine introductions Wutoh et al.
( 1968b) estimated general and specific combining ability components
of variance for nine characters. Genetic advance is possible in flowering
time, maturity date, and seed weight traits, but would be limited for yield,
stolon length, stolon number, and percentage of stolons rooted. Fortunately, yield and flowering time were not correlated. Tinaroo had high general
and low specific combining ability for most traits associated with forage
yield, so should be a valuable parent in breeding for increased yield. Using
six introductions, Wutoh et al. (1968~)studied the inheritance of seven
traits in seven hybrids and their progeny. Hybrid vigor in the F1was not
found in flowering time, stolon number, or percentage of stolons rooted,
but occurred in the other traits followed by inbreeding depression in the
FI. All traits were polygenically controlled, and genotypic correlations
indicated that early flowering, high yield, and good stolon development
could be combined j n one variety.
Slow establishment of glycine appears to be related to poor nodulating
ability. Mode of inheritance of nodulation in glycine is currently being
studied at the Cunningham Laboratory with the aim of developing lines
with rapid and effective nodulation in the field.
Breeding and genetical work at the Cunningham Laboratory is aimed
at developing leucaena lines with high forage yield and a dense, compact,
branching habit suited to grazing. From a diallel cross with four ecotypes,
Gray (1 967a) found that Peru and Guatemala had a greater general combining ability than Hawaii and El Salvador for main stem length. Peru
and Hawaii were superior to El Salvador and Guatemala in general
combining ability for stem number. Gray ( 1 967b) followed inheritance
of a number of characters in all possible crosses between five leucaena
ecotypes. In the F1, leaf size, stem length, and flowering date exhibited
significant genotypic effects, and most F1 means were similar to those of
the higher parent. In the Fe, stem length and number appeared to be controlled by multiple genes affecting vigor, and Fz and FS segregations indicated that branching habit is controlled by two pairs of disomically
inherited genes. Length of main stem and stem number were highly correlated in Fz and F3 progenies of the cross Bald Hills X Guatemala (Gray,
1967c), which suggested that these are not inherited independently but
are related to plant vigor. As predicted from the diallel data, the cross
Peru x Hawaii combining genes for dense branching and high vigor has
given a number of promising new lines.
There is a need to breed mimosine-free lines of leucaena since mimosine is not fully destroyed in the rumen under some conditions. It may be
possible, as Gonzalez et al. ( 1 967) have observed wide variation in mimosine contents in segregating populations from interspecific leucaena
crosses. Plants were selected with less than 30% of the mimosine values
of the leucaena cultivars usually grown.
Breeding and genetical work is warranted with the potentially valuable
I. spicata, especially now that its toxin has been identified by Hegarty
and Pound (1 968). Hutton and Guerassimoff ( I 966) used a red-stemmed
I. spicata type from Ceylon as the male parent in crosses with several
green-stemmed types from the Republics of Congo and Ghana. A number
of F, seedlings died and progeny was obtained from only one F1 plant.
This showed genetic diversity between the parental ecotypes. In the FP
and Fs there was a high degree of sterility, but fertile plants giving fertile progeny were obtained. From these, early flowering lines have been
selected with higher dry matter and seed yields than the parents.
The breeding work with lucerne at the Cunningham Laboratory is
aimed at developing a subtropical grazing lucerne which will grow with
tropical legumes and grasses in a pasture. Selections from the creepingrooted variety Rambler (Heinrichs, 1954) were crossed with the cultivars
Hunter River, Hairy Peruvian, Indian, Pampa, and Saladina. In successive generations Edye and Haydock (1967) found that on a fertile clay
E. M. HUTTON
loan creeping-rooted,ness increased from 2 to 59% and that three times
more creeping-rooted than noncreeping plants persisted. They were also
able to increase both winter and summer yields by mass selection. Subsequent work in two other subtropical environments by Bray ( 1967,1969)
with creeping-rooted clones from the preceding program has confirmed
that creeping-rootedness increased survival. In two polycross populations high positive genotypic correlations were established between
creeping-rootedness and yield at all times of the year, indicating successful selection in early generations. Combinations of the best parental
clones should give synthetic creeping-rooted cultivars with high yield
XI. The Main Grasses
Much of the important cattle country in northeastern Australia is dominated by the perennial native speargrass (Heteropogon contortus) (Shaw
and Bissett, 1955; Tothill, 1966), which is improved markedly in feeding
value by introduction of Townsville stylo (Shaw, 1961). The counterpart of speargrass in a number of monsoonal areas of Africa and Central
and South America is jaraguagrass (Hyparrhenia rufa), which can also
be upgraded by a Stylosanthes species such as S . guyanensis (syn. S .
grucilis) (Stobbs, 1966, 1969b). Most of the grasses planted widely in
improved tropical pastures are African in origin, eastern Africa being
a particularly important source (mgdan, 1966b). Exceptions are the paspalums, native to South America, notably Brazil. Australia and other
countries now have large collections of promising tropical grasses, and
the problem is to sort out the species and ecotypes that will contribute
the most digestible dry matter to the pasture ecosystem.
In this section the relevant facts concerning the agronomy of the main
grasses will be systematized under the different grass genera involved.
With few exceptions they are perennials, and detailed descriptions of
most of them are given by Barnard ( 1967).
The important species in this genus are adapted to the wetter tropical
areas with annual rainfalls of 40-60 inches or more. Paragrass ( B . mutica)
from tropical Africa is the best known and most valuable because of its
tolerance to swampy conditions present in many parts of the tropics. I t is
a perennial with coarse runners rooting at the nodes, which produce erect
shoots with broad hairy leaves. Seed production is poor, and it is usually
planted vegetatively. Under waterlogged conditions it will give a dense,
almost pure stand, its nitrogen supply being derived from drainage or
blue-green algae. Murray lathyroides is one legume that will grow with it
in this type of environment. Where drainage is better, centro and Schofield stylo are suitable associate species. Feeding value of paragrass is
high, and it can be stocked heavily.
Signalgrass (B. decumbens) from Uganda is vigorous and strongly
stoloniferous with bright green leaves: it has distinct promise in northern
Queensland (Schofield, 1944) and other tropical areas. Seed production
is good, but the hard seed needs sulfuric acid treatment to give satisfactory germination. With drainage and fertile soils or nitrogen applications, it will give high liveweight gains per acre.
There is a range of types of B. ruziziensis and also of B. brizantha
(Bogdan, 1955). An ecotype of the first species has been commercialized
in Australia as Kennedy ruzigrass: although it is very hairy, it is very
palatable to stock. B. brizantha has not been used widely but was found
suitable for growing with coconuts in Ceylon.
Buffel (C. ciliaris) is the most important grass in northeastern Australia
because of its drought resistance, adaptability to a range of soils, persistence under heavy grazing, good feeding value, and ease of establishment from seed. I t will become more widely grown in the drier monsoonal
areas of the world. In Australia a number of cultivars have been commercialized: Biloela (Grof, 1957) and Molopo (Flemons and Whalley,
1958) are representative of the tall vigorous rhizomatous types, and
Gayndah (Marriott and Anderssen, 1953) of the shorter nonrhizomatous
types. Seed production of buffelgrass is good, and it is compatible with
legumes like siratro and responds to superphosphate (Edye et al., 1964).
The less vigorous birdwood grass (Cenchrus setigerus) is a better associate for Townsville stylo than buffel (Norman, 1962).
Rhodes (C. gayana) is the only important grass in the genus; its botany,
distribution in Africa, and salient agronomic features are discussed by
Bogdan ( 1969). It seeds prolifically and is a valuable pasture component
south of the Tropic in Australia because of its quick establishment,
stoloniferous habit, adaptability, and cornpatability with a range of
legumes including lucerne (Christian and Shaw, 1952: 't Mannetje,
1967). Rhodesgrass is not as drought resistant as buffet, is salt tolerant
(Teakle, 19371, and responds significantly to high fertility (Henzell,
E. M. HUTTON
1963). It is a variable species, and Bogdan (1969) describes a number of
ecotypes differing in vigor, leaf size, and thickness of stems and stolons.
In Australia the cultivars grown include pioneer, an early type; Katambora, with thin stems and stolons and narrow leaves; Callide (Grof, I96 I),
a coarse vigorous late type; and Samford, which is late, leafy, and
palatable. Milford and Minson (1968b) found no differences in feeding
value between the various Rhodesgrass types.
Common stargrass ( C . dactylon) is widely distributed in east Africa
and is very variable, the ecotypes differing in'size, color (yellowish green
to bluish green), and texture of stems and leaves (Edwards and Bogdan,
1951). Most types are poor seeders but easily spread vegetatively because they are strongly stoloniferous. Some are also rhizomatous. The
forage of stargrass has a relatively high dry matter content and is of high
feeding value. Giant stargrass (incorrectly C. plectostachyus), from the
warmer moist region near Lake Victoria, is giving better animal production than pangolagrass with nitrogen fertilizer in some tropical areas.
A number of stargrass ecotypes have been introduced into Australia,
but none have shown definite promise. Perhaps more work is needed, as
Burton (1947, 1954) successfully developed coastal bermuda which has
become the most important grass in the southeastern United States.
Pangolagrass ( D . decumbens), an aneuploid (2n = 27), is a most important and widely grown species in the tropics; it originated in the
Nelspruit district of the eastern Transvaal (Chippindall, 1955). Oakes
(1960) described its introduction into the United States and its use there
and in the Caribbean, and Hodges et al. ( I 967) discussed its adaptation
to Florida pastures. It is very adaptable and thrives where annual rainfall
is over 40 inches; it is established vegetatively from pieces of its thin
many-noded and vigorously rooting stems. Because of its strongly stoloniferous habit, it rapidly forms a dense stand which resists heavy grazing.
Its high feeding value makes it an ideal grass for a system of nitrogen
fertilization or for growing with a compatible legume like the tree
leucaena. Pangolagrass has been seriously damaged in several countries
by a virus disease first noted in Surinam by Dirvin and Van Hoof ( 1960).
It is also attacked by a number of insects including spittlebug (Prosapia
bicincta), which is a problem in southern Florida (Mead, 1962).
Bryan and Sharpe (1 965) found that growth of pangolagrass in the
Wallum of southeastern Queensland was retarded in winter when
average night temperature was below 58°F. It is possible that, as a result
of Oakes’ (1 965) Digitaria collections from South Africa and studies on
cold tolerance in Digitaria (Oakes and Langford, I967), pangolagrass
may be replaced in some areas with better-adapted types. There is little
doubt that ecotypes of Digitaria smutsii have definite potential and
warrant further work.
Molassesgrass ( M . minut@ora), indigenous to Africa, is the only
species grown, and ecotypes show wide variation in vigor, leafiness, and
growth habit (Bogdan, 1955). It is used extensively in Brazil, and the type
used in Australia came from there. Molassesgrass is a useful pioneer on
well drained areas where annual rainfall is 40 inches or more; it does not
persist under heavy stocking. Leaves are covered with soft short hairs
that exude a sticky substance with a molasseslike odor.
After the buffel cultivars, those of guineagrass or panic (P. maximum)
are the most important grasses in northeastern Australia at present. The
guineagrasses are grown and naturalized throughout the tropical world
and make a significant contribution to animal production in many areas.
In Brazil the tall robust coloniao is valued because of its palatability and
feeding value and its ease of establishment from cuttings and seed. Both
coloniao and the similar hamilgrass are grown in wetter parts of northern
Queensland. Other types grown in northern Australia include the
shorter-growing Gatton and Sabi panics, and Petrie green panic. Of
these, Petrie green panic (Marriott and Winchester, 1951) is the most
important, as it is drought resistant and can be grown in an annual rainfall
as low as 22 inches. It is compatible with a range of legumes and has a
good feeding value because of accumulation of surplus carbohydrate in
the aboveground parts (Humphreys and Robinson, 1966).
Bogdan ( I 955, 1965) in his studies of African ecotypes of P. maximum
found wide variation in vigor and leafiness and classified them into larger
fodder types and smaller grazing types. One interesting type was Embu
creeping guinea which forms a continuous sward because of prostrate
stems which root freely at the nodes.
The closely allied P. coloratum complex contains a range of types with
potential in the subtropics, and several cultivars including the makarikari
grasses Bambatsi, Burnett, and Pollock have been developed (Barnard,
Paspalums are mainly grown in the humid subtropics where annual
rainfall is 30-35 inches or more. Those widely used are common paspalum
or dallisgrass ( P . dilatatum) and bahiagrass ( P . notatum) both natives of
South America. In northern Australia the paspalums used in pastures
include common paspalum, Hartley and Rodd’s Bay plicatulums ( P .
plicatulurn) (Bryan and Shaw, 1964) from Brazil and Guatemala, respectively, and Paltridge scrobic ( P . commersonii) (Paltridge, 1955) from
Rhodesia. Shaw et al. (1965) compared 17 introductions of Paspalum
species and common paspalum in a cutting trial in which optimum growth
was maintained by supplementary irrigation and liberal application of
fertilizers containing nitrogen, phosphorus, and potassium. They found
that P . yaguaronense, P . notatum var. saureae, P . notatum var. latijlorum, and Rodd’s Bay plicatulum were markedly superior in yielding
ability and length of growing season to common paspalum.
Common paspalum, grown with white clover and fertilized with superphosphate, is an important pasture for dairying on the alluvials of northern
New South Wales and southern Queensland. Paltridge scrobic and the
two plicatulums are grown with a range of legumes in coastal areas south
of the Tropic and have proved valuable under waterlogged conditions.
Kikuyugrass ( P . clandestinum), native to a restricted area of the
Kenyan highlands (Edwards and Bogdan, 195 1), has proved to be a very
valuable grass because of its high feeding value, tolerance to heavy grazing, and marked response to nitrogenous and other fertilizers. It requires
an annual rainfall of 35-40 inches or more and thrives on basaltic tablelands throughout the tropics, but at low elevations it is restricted to the
subtropics. Kikuyugrass is strongly stoloniferous and rhizomatous and is
usually established vegetatively. In southeastern Queensland it grows
well with white clover provided it is adequately fertilized with molybdenized superphosphate and potassium chloride (R. E. White, 1967).
There are several ecotypes of kikuyugrass, and commercial seed production of a superior type has been successfully developed in northern
New South Wales (Wilson, 1970).
Elephant- or Napiergrass ( P . purpureum) is indigenous to Africa, particularly Uganda (Edwards and Bogdan, 1951) and is grown in most
tropical countries because of its high yields of palatable forage. It is
vegetatively propagated and needs a high rainfall for best results. Most
types are tall and robust, but Grof ( 1 96 1) developed Capricorn, a shorter
grazing type for north Queensland conditions.
Bulrush millet (Pennisetum typhoides) is a valuable annual fodder crop
grown in the monsoonal tropics. Norman and Begg ( 1 968) have found
cultivars of bulrush millet which give high yields of standover forage for
dry season feeding of cattle in the Northern Territory. The deep rooting
habit of this species enables it to withstand drought and recover nitrate
nitrogen at depth in the soil.
The S . sphacelata complex was reviewed by Hacker and Jones (1 969),
who discussed its botany, natural distribution, agronomy, cytology, and
breeding and its future in Australia. It is widespread in Africa and is very
variable because of its cross-pollinating habit. Various ecotypes have
been studied in Kenya (Bogdan, 1955, 1965); in Australia, Nandi, selected by Bogdan (1959), and Kazungula, developed in South Africa
(Chippindall, 19551, have been commercialized. These cultivars establish
readily from seed, are palatable, and persist under grazing on a wide
range of soils, but they need 35-40 inches or more of annual rainfall for
good production. They combine well with a range of legumes and with
proper management form a stable pasture.
A difficulty with setaria is its oxalic acid content (Dougall and Birch,
1967), which under some conditions can reach a level high enough to
cause oxalate accumulation in the kidneys and death of cattle (Jones
et al., 1970). These conditions need study, as they are liable to occur
occasionally in the field, particularly with cultivars, like Kazungula,
which have a high oxalic acid content.
There has been considerable interest in perennial tetraploid (2n = 40)
sorghums for forage and pasture since the advent of S. afmum (L. R.
Parodi, 1943). Johnsongrass (S. hafepense) in spite of its weed potential
(Roseveare, 1948) has been used as a pasture plant in some countries,
and at the Texas Agricultural Experiment Station perennial sweet sudan
was bred from a cross between it and sudangrass (Hoveland, 1960).
R. A. Parodi and Scantamburlo ( 1 954) continued their work on S. afmum
and developed strains with better yields and less aggressive rhizomes
than the common types. Krish is a perennial diploid (2n = 20) sorghum
selected by Pritchard ( 1 964) at the Cunningham Laboratory from progeny of S. halepense X S . roxburghii (Krishnaswamy et al., 1956).
S . afmum is adapted mainly to the subtropics and thrives on fertile
soils in annual rainfalls of 20-35 inches in a number of countries including Argentine, South Africa, the United States, and Australia. It is a
E. M . HUTTON
useful pioneer and establishes and grows quickly, producing a bulk of
forage of high feeding value. J. G. Davies and Edye ( 1 959) discussed the
agronomy and potential of S . almum in Australia, its genetics and breeding, and the various ecotypes introduced. It is no more cyanogenetic than
other sorghums, so care with grazing is needed only when growth is
stunted. Gates et al. (1966~)showed that three sorghum species, including S . almum, had a high resistance to salinity stress. Crooble (Boyle,
196I), the main cultivar grown in northern Australiz,, is particularly
valuable in the brigalow region. After clearing and burning brigalow
(Acacia harpophylla) and associated trees, a sowing of Crooble in the
ash gives a highly productive pasture for cattle fattening over two years.
Combined with lucerne and barrel medics it provides a pasture for about
four years in rotation with crops like grain sorghum and wheat.
Krish (Pritchard, 1964) combines high yield and palatability with a
degree of frost tolerance and disease resistance. It can be grown in the
wetter coastal areas of southern Queensland, where Crooble is badly
affected with leaf diseases.
The Urochloa species with potential as pasture grasses are U.bolbodes,
U . mosambicensis, and U.pullulans (Miles, 1949; Chippindall, 1955;
Bor, 1960), the last two being naturalized in northeastern Australia. All
are African in origin, and U.mosambicensis is native also to Burma. U .
mosambicensis is considered to have value as an associate for Townsville stylo north of the Tropic in Australia, and commercial seed of one
ecotype is produced. It is very palatable even at maturity when some
greenness is retained. The study of a new range of U . mosambicensis
ecotypes from Africa may result in better-adapted cultivars.
Feeding Value of Grasses versus Legumes
French (1957) in a review on the nutritional value of tropical grasses
notes that the data showed them to be high in fiber and low in crude protein and that work was required on the effects of crude fiber and lignification on organic matter digestibility. The factors involved in the feeding
value of tropical grasses and legumes as determined by indoor feeding
experiments with sheep are discussed by Milford and Minson (1966a,
1966b). Level of animal production from pasture is directly related to its
feeding value, the most important factor being the voluntary intake of dry
matter, which is correlated with dry matter digestibility. Prime determinants of intake are species or variety of pasture plant and its