IC4R003-miRNA-2011-21791435

Project Title

Differential expression of the microRNAs in superior and inferior spikelets in rice (Oryza sativa)

The Background of This Project

[[File:|700px|thumb|right|Figure 1. GWA Analysis of Al Tolerance within and across Rice Subpopulations.]]

• Rice (Oryza sativa) is an important model species of monocotyledon plants with the smallest genome among the major cereals (International Rice Genome Sequencing Project, 2005). As one of the world’s most important staple foods, rice is essential to food security, especially in populous countries of Asia and Africa. In the field of crop science, the product of yield sink capacity and filling efficiency is equal to grain yield in rice (Kato and Takeda,1996). To increase yield, a series of potential high yield rice varieties, such as New Plant Type rice (from the International Rice Research Institute, IRRI) and ‘super’ rice (being developed in China), have been selected and cultivated successively by traditional breeding technology. Although these cultivars generally have a higher yield potential from their larger panicles and numerous spikelets per panicle compared with conventional varieties (Cheng et al., 2007; Kato et al., 2007), often this high yield potential is not realized completely because of poor grain-filling of inferior spikelets (Yang and Zhang, 2010). In general, the later-flowering inferior spikelets of rice are located on secondary rachis branches of the lower primary rachis, while earlier-flowering superior spikelets are located on upper primary rachis branches. Inferior spikelets usually exhibit a slower rate of increase in dry weight during grain development and a lower grain weight than superior spikelets (Iwasaki et al., 1992). Currently, improvement of the grain-filling rate and grain weight in inferior spikelets is one of the major tasks to enhance rice yield.

Research Findings

[[File:|700px|thumb|right|Figure 2. Haplotype analysis of the Nrat1 gene region.]]

Corresponding Author

• Susan R. McCouch(srm4@cornell.edu)