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Restriction fragment length polymorphisms (RFLPs) were studied in fourteen accessions of CCDD genome allotetraploid wild rice species (Oryza latifolia, O. alta and O. grandiglumis). Fourteen nuclear RFLP markers previously mapped in AA genome-cultivated rice were used as probes. A phylogenetic tree, constructed by parsimony analysis based on RFLPs, grouped the accessions according to their geographic origin from Central or South America. Oryza alta, O. grandiglumis and one accession of O. latifolia grouped together as a subgroup, and our results suggested that the three taxa should be considered as populations of a single complex species. Duplicate loci, representing the two constituent genomes of the allotetraploid, were observed for most RFLP markers. By comparing RFLPs from the allotetraploids with those from a CC genome diploid wild species (O. officinalis), it was possible to detect RFLPs specific for both the CC and DD genomes of the allotetraploid. In inter-accession F2 populations, independent segregation of RFLP markers for CC and DD genomes was observed.  相似文献
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Bacterial leaf blight (BB) of rice is a major disease limiting rice production in several rice growing regions of the world. The pathogen, Xanthomonas oryzae pv oryzae, causing the disease is highly virulent to rice crops and is capable of evolving new races. Breeding efforts to incorporate single BB resistant gene often leads to resistance breakdown within a short period. To overcome such breakdown of resistance and develop germplasm with durable disease resistance, we have introgressed three bacterial blight resistance genes, xa5, xa13, and Xa21 into a fine grain rice variety, Samba Mahsuri, using sequence tagged site (STS) markers linked to these genes. Since the efficiency of the STS markers linked to recessive genes to detect homozygotes is less than 100%, we adopted four different pyramiding schemes to minimize loss of recessive resistance genes in advanced backcross generations. Pyramiding scheme A in which a two-gene Samba Mahsuri pyramid line containing Xa21 and xa5 genes was crossed with the Samba Mahsuri line having xa13 gene alone was found to be most effective in preventing the loss of an important recessive gene xa13. We further demonstrated that there was no yield penalty due to pyramiding of multiple genes into the elite indica rice variety.  相似文献
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Key message

A first set of 25 NILs carrying ten BPH resistance genes and their pyramids was developed in the background of indica variety IR24 for insect resistance breeding in rice.

Abstract

Brown planthopper (Nilaparvata lugens Stal.) is one of the most destructive insect pests in rice. Development of near-isogenic lines (NILs) is an important strategy for genetic analysis of brown planthopper (BPH) resistance (R) genes and their deployment against diverse BPH populations. A set of 25 NILs with 9 single R genes and 16 multiple R gene combinations consisting of 11 two-gene pyramids and 5 three-gene pyramids in the genetic background of the susceptible indica rice cultivar IR24 was developed through marker-assisted selection. The linked DNA markers for each of the R genes were used for foreground selection and confirming the introgressed regions of the BPH R genes. Modified seed box screening and feeding rate of BPH were used to evaluate the spectrum of resistance. BPH reaction of each of the NILs carrying different single genes was variable at the antibiosis level with the four BPH populations of the Philippines. The NILs with two- to three-pyramided genes showed a stronger level of antibiosis (49.3–99.0%) against BPH populations compared with NILs with a single R gene NILs (42.0–83.5%) and IR24 (10.0%). Background genotyping by high-density SNPs markers revealed that most of the chromosome regions of the NILs (BC3F5) had IR24 genome recovery of 82.0–94.2%. Six major agronomic data of the NILs showed a phenotypically comparable agronomic performance with IR24. These newly developed NILs will be useful as new genetic resources for BPH resistance breeding and are valuable sources of genes in monitoring against the emerging BPH biotypes in different rice-growing countries.
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