Biology Reference
In-Depth Information
polyploid and frequently aneuploid. Domestica-
tion of sugarcane began several thousand years
ago in Southeast Asia and the Pacific Islands,
where inhabitants chewed its soft stem. Grivet
and colleagues (2004; 2006) recently proposed
a convincing scenario for sugarcane evolution
and domestication in a review compiling his-
torical, botanical, and molecular data, based on
nuclear and mitochondrial probes as well as
molecular cytogenetic evidence. Data generally
do not support any evolutionary path through dis-
tant crosses involving representatives of different
genera. These authors showed that the sugarcane
lineage arose directly from the genus
Saccharum
independent of the closely related genera
Mis-
canthus
and
Erianthus
.The
Saccharum
genus is
divided into six interfertile so-called 'species' (
S.
spontaneum
L.
, S. robustum
Brandes ex Jeswiet
ex Grassl
, S. officinarum
L.
, S. barberi
Jeswiet
,S.
sinense
Roxburgh and
S. edule
Hasskarl.). Basi-
cally sugarcane emerged from an initial diver-
gence between the two ancestral wild species
S.
robustum
(2
n
Yield Increase Brought by Wild
Introgressions
The second step of yield improvement relied on
the 100 years of breeding that began at the end
of the 19
th
century with the exploitation of sug-
arcane fertility (Figure 13.3). The first breeding
stations were established in Barbados and Java at
the end of the 1880s (Daniels and Roach 1987).
After making efforts aimed at intraspecific
breeding within
S. officinarum
, breeders rapidly
observed that interspecific crosses between
S.
officinarum
and
S. spontaneum
were better able
to overcome the diseases that threatened sugar
industries. Adding
S. spontaneum
in the crosses
provided resistance to mosaic and Sereh, both
serious diseases that occurred in the 1920s.
Agronomic
performance
was
also
improved
because
of
S.
spontaneum
's
good
ratooning
=
6
x
-8
x
=
60-80) and
S. spontaneum
(2
n
40-128) that have high fiber but
very low sugar content.
S. spontaneum
comprises
highly polymorphic phenotypes with many ane-
uploid forms and is considered to be autopoly-
ploid.
S. officinarum
(2
n
=
5
x
-16
x
=
80), with its juicy,
sugar-rich, thick stalk called 'noble cane,' was
domesticated by ancestral Melanesian popula-
tions in New Guinea from a particular cytotype
of
S. robustum
. The two other sugar-producing
domesticated
'
species,'
S. barberi
(2n
=
8
x
=
=
104 to
128) and
S. sinense
(2n
81 to 124), formerly
cultivated in Asia, have been shown to be natural
hybrids between
S. officinarum
and
S. sponta-
neum
(D'Hont et al. 2002). Sugarcane domesti-
cation was the first stage of yield increase, which
provided cultivated forms with high productive
potential owing to their thick stalk that accu-
mulated large amounts of sucrose. Two of the
three sweet domesticated species,
S. barberi
and
S. officinarum
, spread throughout intertropical
areas, thanks to human migration and European
colonization.
S. officinarum
was the main culti-
vated species until the end of the 19
th
=
Fig. 13.3.
Schematic breeding history of sugarcane, show-
ing a second significant step in yield improvement in the 20
th
century. Modern cultivars (
Saccharum
spp.) rely on a few
crosses undertaken 100 years ago between
S. officinarum
(the high-sucrose domesticated species) and
S. spontaneum
(a wild species without sucrose), involving a limited num-
ber of founders. These first interspecific hybrids were back-
crossed with the high-sucrose species, and subsequently com-
plex recurrent intercrossing of the best products gave rise to
modern cultivars. For a color version of this figure, please
refer to the color plate.
century.
Search WWH ::
Custom Search