Two eyespot resistance genes (Pch1 and Pch2) have been characterised in wheat. The potent resistance gene Pch1, transferred from Aegilops ventricosa, is located on the distal end of the long arm of chromosome 7D (7DL). Pch2 derives from the variety Cappelle Desprez and is located at the distal end of chromosome 7AL. The RFLP marker Xpsr121 and the endopeptidase isozyme allele Ep-D1b, are very closely linked to Pch1, probably due to reduced recombination in the region of the introgressed A. ventricosa segment. Pch2 is less closely linked to these markers but is thought to be closer to Xpsr121 than to Ep-A1b. In the present study simple sequence repeat (SSR) markers were integrated into the genetic map of a single chromosome (7D) recombinant (RVPM) population segregating for Pch1. Sequence-tagged-site (STS)-based assays were developed for Xpsp121 and a 7DL wheat EST containing a SSR. SSR markers Xwmc14 and Xbarc97 and the Xpsr121-derived marker co-segregated with Pch1 in the RVPM population. A single chromosome (7A) recombinant population segregating for Pch2 was screened for eyespot resistance and mapped using SSRs. QTL interval mapping closely associated Pch2 with the SSR marker Xwmc525.

Leaf chlorophyll content is an important physiological indicator of plant growth, metabolism and nutritional status, and it is highly correlated with leaf nitrogen content and photosynthesis. in this study, we report the cloning and identification of a xylan glucuronosyltransferase gene (OsGUX1) that affects relative chlorophyll content in rice leaf. Using a set of chromosomal segment substitution lines derived from a cross of wild rice accession ACC10 and indica variety Zhenshan 97 (ZS97), we identified numerous quantitative trait loci for relative chlorophyll content. one major locus of them for relative chlorophyll content was mapped to a 10.3-kb region that contains OsGUX1. the allele OsGUX1 AC from ACC10 significantly decreases nitrogen content and chlorophyll content of leaf compared with OsGUX1 ZS from ZS97. The overexpression of OsGUX1 reduced chlorophyll content, and the suppression of this gene increased chlorophyll content of rice leaf. OsGUX1 is located in Golgi apparatus, and highly expressed in seedling leaf and the tissues in which primary cell wall synthesis occurring. our experimental data indicate that OsGUX1 is responsible for addition of glucuronic acid residues onto xylan and participates in accumulation of cellulose and hemicellulose in the cell wall deposition, thus thickening the primary cell wall of mesophyll cells, which might lead to reduced chlorophyll content in rice leaf. These findings provide insights into the association of cell wall components with leaf nitrogen content in rice.Rice (Oryza sativa. L) providing a staple food for more than half of the population in the world, is a monocot model species for genetics, biology and functional genomics studies. Leaf photosynthesis has great potential for the improvement of rice yield, which will significantly contribute to addressing food demand challenge. The chloroplast of green tissue or leaf, as the most important supporter of carbon fixation and energy transformation, plays important roles in photosynthesis 1-3 . Both genetic and environmental factors have effect on the biochemical composition in chloroplast, thus affecting photosynthetic rate 4 .Previous studies have indicated that leaf color is a sensitive indicator of crop growth, metabolism and nutritional status, and it is closely related to the content of photosynthetic pigment, and positively correlated with leaf nitrogen (N) content 5-7 . Understanding the genetic and physiological bases of leaf nitrogen status is essential for efficient crop production and nitrogen management in intensive rice cropping systems. Leaf greenness is determined by specific properties, such as leaf chlorophyll content and chloroplast development, and leaf morphological characteristics (leaf thickness, surface structure and wall components). To study the genetic and molecular basis of leaf color, more than one hundred of rice mutants associated with leaf colors and chlorophyll content have been identified (http://archive.gramene.org/db/genes/). Several genes have been implicated in the chlorophyl...