Sugar Cane: Past and Present
By Peter Sharpe
Sugar cane is composed of six species of perennial grasses
of the genus Saccharum L., in tribe Andropogoneae of the
Gramineae. There are two wild species, S. spontaneum L.
and S. robustum Brandes & Jeswiet ex Grassl, and 4 cultivated
species, S. officinarum L., S. barberi Jeswiet, S. sinense Roxb.,
and S. edule Hassk. (Purseglove 1979). The four cultivated
species are complicated hybrids, and all intercross
readily. All commercial canes grown today are inter-specific
hybrids (Wrigley 1982).
DISTRIBUTION
Sugar cane is believed to have originated in the South
Pacific. S. spontaneum occurs in the wild from eastern and
northern Africa, through the Middle East, to India, China,
Taiwan, and Malaysia, and through the Pacific to New Guinea. The
center of origin is probably in northern India where forms with
the smallest chromosome numbers occur. S. robustum is found along
river banks in New Guinea and some of its adjacent islands and is
indigenous to the area. S. officinarum (or noble cane) most
likely originated in New Guinea. This cane is only suited for
tropical regions with favorable climate and soil. S. barberi
probably originated in India. S. sinense occurs in portions of
India, Indo-china, southern China and Taiwan. S. edule is thought
to be a sterile form of S. robustum and is found only in New
Guinea and nearby islands (Purseglove 1979).
Cane sugar is currently grown primarily in tropical regions.
The highest latitudes at which cane is grown is in Natal,
Argentina and at the southern extremes of the Australian industry
(approximately 30 degrees S), and at 34 degrees N in northwest Pakistan, and 37 degrees N in southern Spain (Jenkins 1966).
HISTORICAL RECORD
Sugar cane has been known for at least 2200 years.
Alexander's army saw sugar cane during its conquest of India in
326 BC (Purseglove 1979). Nearchus mentioned sugar cane in
western India in 325 BC. Sugar cane was probably introduced into
China around 110 BC when a botanical garden was founded near
Pekin for the introduction of exotic-plants (Deerr 1949).
Theophrastus described 'honey produced from reeds,' while
Dioscorides, in the first century AD, described 'a honey called
sakkharon collected from reeds in India and Arabia Felix with the
consistency of salt and which could be crunched between the
teeth'. The mountains and deserts of Afghanistan, Baluchistan,
and eastern Persia served as natural barriers against the spread
of cane to other areas for centuries. It eventually reached
Persia in the sixth century. The Arabs were responsible for much
of its spread as they took it to Egypt in 641 AD during their
conquests. They also carried it with them as they advanced around
the Mediterranean. Sugar cane spread by this means to Syria,
Cyprus, and Crete, eventually reaching Spain around 714 AD. The
sugar industry in Spain was very successful, with about 30,000 ha
of cane being cultivated by about 1150 AD. Around 1420 the
Portuguese introduced cane into Madeira, from where it soon
reached the Canary Islands, the Azores, and West Africa
(Purseglove 1979). Columbus transported sugar cane from the
Canary Islands to Hispaniola (now the Dominican Republic) on his
second voyage in 1493 (Deerr 1949, Purseglove 1979).
The first New World sugar cane mill began grinding in about
1516 in the Dominican Republic. Sugar production spread to Cuba,
Jamaica, Puerto Rico, and the other Greater Antilles by the end
of the 1500's (Hagelberg 1985).
PROPAGATION
Sugar cane propagation is through stem cuttings of immature
canes 8-12 months old. These are called "setts", "seed", "seed-
cane" or "seed-pieces". The setts are best if taken from the
upper third of the cane because the buds are younger and less
likely to dry out. The setts can be planted at a 45 degree angle
or laid horizontally in a furrow. It takes 12,500 - 20,000 setts
to plant one hectare (Purseglove 1979). The setts are lightly
covered with soil until they sprout (10-14 days) and then the
sides of the furrow are turned inward (McIlroy 1963). Sugar cane
is a perennial crop which usually produces crops for about 3-6
years before being replanted. The first crop is called the
"plant crop" and takes 9-24 months to mature, depending on
location (Purseglove 1979). Reaping is usually done by hand with
a cutlass, although mechanical harvesters are being developed.
The cane is cut close to the ground because the lower stem has
the highest sugar content and it aids in ratooning, the emergence
of new crops from the stems and trash (leaves and tops) left
behind (McIlroy 1963). Ratoon crops take about one year to
mature. As many as four or more ratoon crops may be produced
before replanting is necessary, mostly due to the slow decline in
yields (McIlroy 1963, Purseglove 1979).
DISEASES AND PESTS
There are many diseases and pests which may effect sugar
cane. Bacterial diseases include gumming disease, Xanthomonas
vasculorum (Cobb) Dows., in which yellowish stripes occur at the
leaf tips and the vascular bundles exude a yellowish gum when
cut, and leaf scald, Xanthomonas albilineans (Ashby) Dows., in
which yellow stripes occur on the leaf blade, many side-shoots
are produced, and the vascular bundles of the stalk are red
(Purseglove 1979).
Fungal diseases such as red rot (Colletotrichum falcatum
Went), root rot (Pythium graminicolum Subr.), pineapple disease
(Thielaviopsis parodoxa (de Seynes) C. Moreau), downy mildew
(Sclerospora sacchari Miy), and smut (Ustilago scitaminea Syd.)
can also cause damage. Red rot causes the setts to be seriously
damaged at low temperatures. Root rot was responsible for the
failure of "Otaheite" (a noble cane) in Mauritius in 1846 and
several other areas later. Pineapple disease attacks the setts
causing the center to turn black and smell like overripe
pineapples. Downy mildew is currently only found in the western
Pacific and was responsible for severe losses in Queensland until
rigorous controls were initiated. Smut causes black whiplike
organs to emerge from the center of the leaf-roll and is important in southeastern Asia and South Africa (Purseglove 1979).
Mosaic is a viral disease, whose vectors include Aphis
maidis Fitch, was first recognized in Java in 1892 and causes
severe stunting in some cases. other viral diseases include
ratoon stunting, chlorotic streak, Fiji disease, and Sereh
disease (Purseglove 1979).
The most destructive insects of sugar cane are stem-borers,
the larvae of several genera of moths. The larvae burrow into
the stem and on emergence cause loss of sucrose and weakened
stems. Biological control, the use of natural parasites, is the
most effective control for these (Purseglove 1979).
Other pests include termites in India and white grubs in
Queensland. Rats are also a problem in many areas, for they eat
the cane and introduce pathogens. The Indian mongoose, Herpestes,
was introduced in the West Indies around 1870. This was a
failure because they found they were able to catch birds easier
(Purseglove 1979).
BREEDING
All species of sugar cane are easily crossed. There are
also reported crosses of sugar cane with, other genera, such as
Zea and Sorghum, although none are of commercial value at the
present (Wrigley 1982). Flowering cane is not desirable in
commercial plantations because it indicates the end of vegetative
growth and sugar production. Flowering can be avoided by
extension of day-length by exposure of the cane to electric
lights for short periods at night during the time when flowering
usually occurs, therefore extending the productive life of the
cane (McIlroy 1963). The greatest advance in sugar cane breeding
came in 1888 when it was realized that sugar cane could set
fertile seed which could be used to produce better cane
varieties. Prior to this it was believed that all cane was
sterile because one of the varieties of S. officinarum, Creole
cane, which was the only variety known in the Western world for a
long time, was sterile (Deerr 1949). The original breeding
stations were in areas where cane flowers naturally, but are now
found in many areas due to techniques such as manipulation of day
length and temperature (Wrigley 1982). The pollen grain has a
short viability, as does the seed. However, the flowers seldom
set the 1 mm long seeds (McIlroy 1963). About 1 in 10,000
seedlings resulting from the thousands of crossings made annually
is worth selection for trials, and less than 1 in 10 of these is
likely to become a commercial variety (Wrigley 1982).
The goal of cane breeding is to produce an economic yield of
sugar sustained over several ratoons. Sugar canes are highly
polyploid, wind pollinated outbreeders. They are clonally
propagated, highly heterozygous, and intolerant to inbreeding.
New varieties are sought from the first generation progeny of
crosses between clones. There are five species of interest to
cane breeders. S. officinarum (2n=80) has good sugar quality and
low fiber, although it is susceptible to most of the main
diseases, except gumming disease and smut. S. spontaneum
(2n=40-128) is a source of resistance to many diseases, including
"Sereh", mosaic, gumming, red rot, and downy mildew. S. barberi
(2n=82-124) are considered the most important breeding canes and
are immune to gumming and mosaic and resistant to downy mildew,
but susceptible to smut and red rot. S. sinense (2n=82-124) is
difficult to breed, but has given rise to some useful breeding
lines. S. robustum (2n=60-194) has been used to some extent in
breeding lines (Wrigley 1982).
Breeding and selection of cane is not a simple process since
viable seeds are seldom produced. Breeding occurs at the
experiment stations which are able to provide the proper
conditions and techniques required. The setts of new varieties
are then distributed to the cane growers. Through selective
breeding the yield has been increased by 85%.
YIELDS
Sugar cane yields the highest number of calories per unit
area of any plant (Heiser 1981), producing up to 10 tons of
sucrose per hectare in Barbados. Trinidad produces 90-120 tons
of millable cane per hectare from the plant crop and 45-90 tons
from ratoons. The highest yields of 22 tons of sucrose per
hectare occur in Hawaii, but the crops take two or more years to
mature there. Recovery of raw sugar from cane varies from 11-13
percent (Purseglove 1979). In 1980 the world production of sugar
from cane and beets was about 86 million tons. Almost 65% of this
(about 55.5 million tons) came from cane (Paturau 1982).
Substantial increases in yields have occurred over the past 100
years due to improved cultural practices, particularly fertilizer
use, disease and pest control, field and factory. mechanization,
and breeding of higher-yielding varieties.
PROCESSING AND USES
Sugar cane was originally grown for the sole purpose of
chewing in southeastern Asia and the Pacific. The rind was
removed and the internal tissues sucked or chewed. Noble canes
are the best for chewing due to high sugar and juice contents.
Production of sugar by boiling the cane juice was first
discovered in India, most likely during the first millennium BC
(Purseglove 1979).
Today, sugar cane has many industrial uses and is one of the
most widely used and cheapest domestic products (Jenkins 1966).
In sugar factories the harvested cane is shredded and crushed
with heavy rollers to retrieve the juice which contains 10-20%
sucrose. The pH is raised with lime and the mixture is heated to
around 100 degrees C for several hours. The lime causes suspended
materials, proteins, waxes, and fats to precipitate. Further
impurities are allowed to settle in large containers and are
removed from the bottom. This residue is known as filter cake or
filter mud. The clear juice is again heated in a series of
evaporators to form crystals and separated from the molasses in
centrifuges. About 1 ton of raw sugar can be extracted from 8-9
tons of cane (McIlroy 1963). This raw brown sugar can be further
refined to produce white sugar (Heiser 1981).
Sugar cane has many other uses besides the production of
sugars. Molasses is a by-product of the manufacturing of cane
sugar. It is a residual syrup from which no more crystalline
sucrose can be obtained by simple techniques. Approximately 2.7%
of a ton of cane can be extracted as molasses. In 1980 nearly
30.8 million tons of molasses were produced, with Brazil leading
production with about 5.2 million tons (Paturau 1982). The uses
of molasses are many.
Starting around 1850 it was often used as a fertilizer for
cane soils, however this use is negligible today. Its use as a
stockfeed can be dated back to at least 1811 in Germany. Today,
at least 600,000 tons are used annually in the U.S. alone. Its
most important feed characteristic is its high carbohydrate
contents (Paturau 1982).
Molasses can also be distilled and fermented to produce
various items. Molasses, along with cane juice and other
by-products can be fermented to produce an alcoholic distillate,
otherwise known as rum. Rum, or very similar liquors, are written
about as far back as 2000 BC. It can also be traced back to the
colonization of the West Indies in the 1600's. Ethyl alcohol
(ethanol) is another alcohol produced from molasses, which in
itself has many uses. The main uses are in vinegar, cosmetics
and pharmaceuticals, cleaning preparations and solvents, and
coatings. One of the future uses of ethanol which is currently
being studied is as a gasoline extender. Still other products
produced from molasses are butanol (a solvent), lactic acid (a
solvent), citric acid (mostly for foods and beverages), glycerol,
yeast, and many others (Paturau 1982).
Another useful by-product of sugar production is bagasse,
the fibrous residue left after the juices are extracted from the
cane. It is the main source of fuel in sugar factories. It can
also be used in making paper, cardboard, fiber board, and wall
board (Purseglove 1979).
The filter mud can contain up to 15% cane wax. When
extracted, this wax can be used in the production of polishes and
insulation. Only about one ton of wax is obtained from 1,000 tons
of cane, so the process is economically feasible only under
certain circumstances (McIlroy 1963).
It is quite possible that further uses of sugar cane will be
developed in the future, but even now it can be seen that sugar
cane is a very important and useful plant crop worldwide.
LITERATURE CITED
Deerr, N. 1949. The history of sugar. Vol. 1. Chapman and Hall Ltd.,
London. 258 pp.
Hagelberg, G.B. 1985. Sugar in the Caribbean: turning sunshine into
money. The Woodrow Wilson International Center for Scholars,
Washington, D.C. 42 pp.
Heiser, C.B. 1981. Seed to civilization: the story of food. Second ed.
W.H. Freeman and Co., San Francisco. 254 pp.
Jenkins, G.H. 1966. Introduction to cane sugar technology. Elsevier
Publishing Co., New York. 478 pp.
McIlroy, R.J. 1963. An introduction to tropical cash crops. Ibadan
University Press, Nigeria. 163 pp.
Paturau, J.M. 1982. By-products of the cane sugar industry. Second ed.
Elsevier scientific Publishing Co., New York. 366 pp.
Purseglove, J.W. 1979. Tropical crops: monocotyledons. Longman Group
Ltd., London. 607 pp.
Wrigley, G. 1982. Tropical agriculture: the development of production.
Fourth ed. Longman Inc., New York. 496 pp.
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