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The brown planthopper (BPH) is a major insect pest in rice, and damages these plants by sucking phloem-sap and transmitting viral diseases. Many BPH resistance genes have been identified in indica varieties and wild rice accessions, but none has yet been cloned. In the present study we report fine mapping of the region containing the Bph1 locus, which enabled us to perform marker-aided selection (MAS). We used 273 F8 recombinant inbred lines (RILs) derived from a cross between Cheongcheongbyeo, an indjca type variety harboring Bph1 from Mudgo, and Hwayeong-byeo, a BPH susceptible japonica variety. By random amplification of polymorphic DNA (RAPD) analysis using 656 random 10-mer primers, three RAPD markers (OPH09, OPA10 and OPA15) linked to Bph1 were identified and converted to SCAR (sequence characterized amplified region) markers. These markers were found to be contained in two BAC clones derived from chromosome 12: OPH09 on OS-JNBa0011B18, and both OPA10 and OPA15 on OS-JNBa0040E10. By sequence analysis of ten additional BAC clones evenly distributed between OSJNBa0011B18 and OSJNBa0040E10, we developed 15 STS markers. Of these, pBPH4 and pBPHU flanked Bph1 at distances of 02 cM and 0.8 cM, respectively. The STS markers pBPH9, pBPH19, pBPH20, and pBPH21 co-segregated with Bph1. These markers were shown to be very useful for marker-assisted selection (MAS) in breeding populations of 32 F6 RILs from a cross between Andabyeo and IR71190, and 32 F5 RILs from a cross between Andabyeo and Suwon452. [ABSTRACT FROM AUTHOR]

Salt tolerance was evaluated at the young seedling stage of rice (Oryza sativa L.) using recombinant inbred lines (MG RILs) from a cross between Milyang 23 (japonica/indica) and Gihobyeo (japonica). 22 of 164 MG RILs were classified as tolerant with visual scores of 3.5-5.0 in 0.7% NaCl. Interval mapping of QTLs related to salt tolerance was conducted on the basis of the visual scores at the young seedling stage. Two QTLs, qST1 and qST3, conferring salt tolerance, were detected on chromosome 1 and 3, respectively, and the total phenotypic variance explained by the two QTLs was 36.9% in the MG RIL population. qST1 was the major QTL explaining 27.8% of the total phenotypic variation. qST1 was flanked by Est12~RZ569A, and qST3 was flanked by RG179~RZ596. The detection of new QTLs associated with salt tolerance will provide important information for the functional analysis of rice salt tolerance. [ABSTRACT FROM AUTHOR]

Presents a study which described the cyclic activity of a maize transposable element dissociation (Ds) in rice. Materials and methods used; Inactivation of the Ds element in rice; Reactivation of Ds and the expression pattern of activator; Comparison of Ds and the retrotransposable element Tos17.