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Sorghum [Sorghum bicolor (L.) Moench] ranks fifth among cereals in both production and area planted worldwide (http://faostat.fao.org/), and is particularly important to food security in the semi-arid zones of Western and Central Africa because it is adapted to hot and dry agroecologies. It is grown primarily for its grain, but the leaves and stalks are also used for fodder and as building material. Most landraces from tropical regions are photoperiod-sensitive and flower only under short daylength conditions, often attaining very large height before flowering, while breeding material and cultivars from temperate regions have been selected to be short and daylength-neutral (see Germplasm).
Sorghum is a panicoid grass closely related to sugarcane (divergence time ~5 MY) and maize (divergence time ~12 MY), and less closely related to rice (divergence time ~50 MY), although considerable synteny remains. Sorghum’s evolutionary relationship to maize and rice provides many opportunities for comparative studies addressing basic questions about plant development and metabolism that are common to the grasses.
Compared to maize, sorghum has limited haplotype diversity and a moderate extent of linkage disequilibrium which, together with its relatively small genome size and extensive morphological and physiological variation, make it very well-suited to association mapping methods for identification of functional diversity.
Many genetic resources are available for sorghum: genetic and physical maps, a large collection of ESTs, and a US germplasm collection of about 40,000 accessions. The complete genome sequence is being determined by JGI and should be available by the end of 2006.
| species |
genome size |
carbon fixation metabolism |
outcrossing rate |
| sorghum |
760 Mb |
C4 |
1-15% |
| maize |
2500 Mb |
C4 |
95% |
| rice |
430 Mb |
C3 |
1% |
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