A QTL cluster for plant architecture and its ecological significance in Asian wild rice

The wild progenitor (Oryza rufipogon) of Asian rice (Oryza sativa) shows a wide range of variations in life-history traits, forming an annual-perennial continuum. A conspicuous feature of an annual type of wild rice is represented by its adaptability to disturbed habitats, and its short stature with many tillers and a prostrate growth habit. The present study was carried out to examine the genetic differentiation between wild annual and cultivated (Japonica type) rice strains by quantitative trait locus (QTL) analysis. In total, 20 adaptive and/or domestication-related traits were evaluated in recombinant inbred lines (RILs). A total of 28 putative QTLs were detected across the genome. Six QTLs responsible for plant architecture were located on the short arm of chromosome 7. The near-isogenic line with the region containing the QTL cluster confirmed that the QTLs exerted a significant effect on the plant architecture in the genetic background of cultivated rice. A similar QTL cluster was also found in another annual strain of a different origin, suggesting that the QTL cluster might be predominant in annual wild rice. Furthermore, a QTL for tolerance to disturbance (simulated trampling) was detected within the region of the cluster on chromosome 7. These results are discussed in relation to their ecological significance in wild annuals of rice.