Oryza officinalis Complex

Abstract

Oryza officinalis complex is the largest species complex within the genus Oryza, consisting of both diploid and allotetraploid species. It contains at least ten reported perennial species (O. officinalis, O. rhizomatis, O. eichengeri, O. minuta, O. malampuzhaensis, O. punctata, O. latifolia, O. alta, O. grandiglumis, O. schweinfurthiana and O. australiensis) distributed throughout the tropics. Most of the allotetraploid species in this group have originated recently, and their progenitors are also naturally available in many cases. This provides a unique opportunity to study evolution of polyploidy within the genus Oryza. Classical cytogenetic techniques like karyotyping, meiotic pairing have provided valuable information in this regard. Most of the diploid and allotetraploid species contain ‘C’ genome except diploid O. punctata (BB) and O. australiensis (EE). Till date, whole genome sequence is available only for O. punctata and rest are under progress. Considerable success has been achieved in terms of developing genetic stock through wide hybridization and mapping agronomically important genes from the species of O. officinalis complex. Successful introgressions of brown plant hopper resistance and bacterial leaf blight resistance to the cultivated varieties have been achieved from these genetic stocks. Molecular marker resources to facilitate such alien gene introgression events are becoming more and more available. In order to address the problem of world food security, global importance has been laid on utilization of wild resource in rice. With focused objectives and rapidly emerging scientific and technological know-how, we can expect much more efficient utilization of the O. officinalis complex in future rice improvement.