Patancheru, India
February 2, 2009
The announcement of the unraveling
of the genome of sorghum, one of the mandate crops of the
International Crops Research
Institute for the Semi-Arid Tropics (ICRISAT), will
strengthen the Institute’s research for the improvement of
sorghum and other food crops.
The sequencing of the sorghum genome was announced in a
scientific article published on 29 January 2009 in the journal
Nature. The global team of scientists that reported the genome
sequencing was led by Prof Andrew Paterson of the University of
Georgia, USA, and included ICRISAT’s Cereal Breeder, Dr C Tom
Hash.
Sorghum is the second food crop from the grass family to have
its genome fully sequenced. The first one was rice. Sorghum is
the first crop with the more efficient C4 photosynthesis system
to be sequenced. Sugarcane, maize and pearl millet are other
grasses with the C4 photosynthesis system that should benefit
from this.
Plants that have a C4 photosynthesis system have a competitive
advantage over plants possessing the more common C3 carbon
fixation pathway under conditions of drought and high
temperatures. While a significant portion of the water taken up
by C3 plants is lost through transpiration, this loss is much
lower for C4 plants, demonstrating their advantage in a dry
environment.
According to Dr William Dar, Director General of ICRISAT, the
unraveling of the sorghum genome is the first such breakthrough
for a dryland agricultural crop that is adapted to drought. “The
sequence of sorghum genome will provide us a better
understanding on genes that make sorghum, as compared to other
cereals, more drought tolerant.”
ICRISAT will combine the new knowledge on the sorghum genome
sequence with its expertise on molecular-marker assisted crop
selection and breeding to develop improved sorghum varieties and
hybrids for desirable traits, say with improved drought
tolerance or improved disease resistance.
Candidate genes identified for drought tolerance or pest
resistance can be used to understand natural variation in
ICRISAT’s sorghum germplasm collection comprising of more than
36,000 accessions with a final objective to identify superior
variants for using in breeding crops.
The genome sequence is already contributing to development of
additional molecular markers for economically important sorghum
traits, and for identification of specific genes that control
them. This in turn is leading to more efficient crop breeding
methods – particularly those based on marker-assisted selection
for naturally occurring genetic variation – which will reduce
the time required to develop grain, forage, and sweet sorghum
varieties and hybrids having improved agronomic performance,
stress tolerance, pest resistance and product quality.
The availability of genome sequence data should enhance
genomics-assisted breeding in sorghum. For instance, a few
hundred molecular markers, genomics tools that are used in
marker-assisted selection, were available in sorghum until 2 to
3 years ago; genome sequence data has now provided more than
71,000 microsatellite marker candidates.
“We believe that availability of genome sequence combined with
modern genomics approaches should boost our breeding activities
to develop the desirable breeding lines. Genes identified in
sorghum would not be useful only for sorghum but other
cereal/plant species as well, especially for enhancing drought
tolerance,” Dr Dar said.
The paper published in Nature shows that different cereals such
as rice, wheat, barley, maize, sorghum and pearl millet show
similarities in gene number and gene order, since they derived
from a common ancestor. This allows the use of genomic resources
from one cereal species to improve another species. For
instance, based on the sequence data of sorghum and rice,
molecular markers have been developed and are being used in
pearl millet, another mandate crop for ICRISAT.
Sorghum, a mandate crop of ICRISAT, is the fifth most important
and relatively drought tolerant cereal crop that is the dietary
staple of more than 500 million people in more than 30 countries
of semi-arid tropics. It is grown on 42 m ha in 98 countries of
Africa, Asia, Oceania, and the Americas.
ICRISAT has been working for more than three decades for
improving sorghum for food and feed proposes. Furthermore, sweet
sorghum has emerged as a feedstock for ethanol production. It
gives food/feed, fodder and fuel, without significant trade-offs
in any of these uses in a production cycle. ICRISAT has
pioneered the sweet sorghum ethanol production technology, and
its commercialization.
Having the genome sequence of sorghum is significant landmark of
genomics research for sorghum community in particular and
biofuel community in general. |
|
