QTLs analysis of rice peduncle vascular bundle and panicle traits

The vascular bundle in plants plays an important role intransportation of photosynthetic products, mineral nutri-ents, water, arid so on. Significant positive correlationswere found between grain yield, panicle traits and the No.of peduncle vascular bundles. So, it is very important tostudy the inheritance of peduncle vascular bundle, whichis a quantitative trait.

QTLs for ovicidal response to whitebacked planthopper in rice

Japanese japonica rice commonlyprovides with an ovicidal resistanceagainst the whitebacked planthopper(WBPH). Similarly, ovicidal activi-ty was also found to play a significantrole in a stable field resistance toWBPH in some Chinese japonicarice. Rice varieties with ovicidal re-

Characterization and mapping of a white panicle mutant gene in rice

A spontaneous white panicle mutant was found from the F6 progenies of an indica/japonica cross. The mu-tant exhibits white stripes on its basal leaves while the pani-cles, rachis and pedicel are milky white colored at flowering stage. Genetic analysis in an F2 population from the cross of Zhi7/white panicle mutant indicates that the white panicle phenotype is controlled by a single recessive nuclear gene, tentatively termed as wp(t). Using microsatellite markers, the wp(t) gene was anchored between the markers of SSR101 and SSR63.9 with a map distance of 2.3 and 0.8 cM, respec-tively, and co-segregated with the marker of SSR17 on rice chromosome 1.

Analysis of rice blast resistance genes by QTL mapping

Resistance to rice blast pathogen mostly shows a quantitative trait controlled by several minor genes. Its complexity and the mutable characteristic of rice blast iso-lates both hinder the development of the blast resistance re-search. The article here tried to explore the resistance gene distribution on rice chromosomes and the way of function. Totally 124 QTLs have been identified against 20 isolates using Cartographer software with a ZYQ8/JX17 DH popula-tion, which separately are at 100 loci of 72 marker intervals on 12 rice chromosomes. Of them, 16 QTLs were determined by the isolate HB-97-36-1. 82 QTLs (66.13%) are from the resistant parent alleles, ZYQ8, while 42 QTLs (33.87%) are from the susceptible parent alleles, JX17. In comparison of their positions on chromosome, most QTLs are clustered together and distributed nearby the major genes especially the regions on chromosomes 1, 2, 8, 10 and 12. Each QTL could account for the resistance variation between 3.52%—68.64%. And, a positional QTL might display the resistance to several different isolates with different contributions.

Characterization and mapping of a lesion mimic mutant in rice (Oryza sativa L.)

A rice initiation-type lesion mimic mutant (imi) was identified, which was isolated from an indica rice Zhongxian 3037 through γ radiation mutagenesis. Trypan blue staining and sterile culture revealed that the mutant spontaneously developed lesions on the leaves in a develop mentally regulated and light-dependent manner. Genetic analysis indicated that the lesion mimic trait was controlled by a single resessive locus. Using public molecular markers and an F2 population derived from lmi and 93-11, we mapped the lmi locus to the short arm of chromosome 8, nearby the centromere, between two SSR markers RM547 and RM331. The genetic distance was 1.2 and 3.2 Cm, respectively. Then according to the public rice genomic sequence between the two SSR markers, lmi was further finely tagged by three CAPS markers: C4135-8, C4135-9 and C4135-10. And lmi locus was a co-segregated with marker C4135-10, providing a starting point for imi gene cloning.

Genetic analysis and fine mapping of a lax mutant in rice

We have analyzed a lax mutant that exhibits altered panicle architecture in rice. The primary and secondary rachis-branches are normally initiated and each branch ends in a terminal spikelet, but all the lateral spikelets are absent and the terminal spikelet displays variegated structures in the mutant. An F2 population from the cross between the lax mutant and a japonica variety, W11, was constructed and analyzed. Using microsatellite and CAPS markers, the lax locus was mapped on the long arm of chromosome 1, co-segregated with a CAPS marker, LZ1, within an interval of 0.28 cM between a CAPS marker, HB2, and a microsatellite marker, MRG4389. RT-PCR analysis revealed that the expressions of the rice B-function MADS-box genes OsMADS2, OsMADS4, OsMADS16 and OsMADS3 were significantly reduced, whereas the expression of the rice A-function gene RAP1A was not altered.

Identification and gene prediction of a 24 kbregion containing xa5,a recessive bacterial blight resistance gene in rice(Oryza sativa L.)

Rice xa5 gene provides recessive, race-specific resistance to bacterial blight disease caused by the pathogen Xanthomonas oryzae pv. oryzae and has great value for re-search and breeding. In an effort to clone xa5, an F2 popula-tion of 4892 individuals was developed from the xa5 near isogenic lines, IR24 and IRBB5. A fine mapping procedure was conducted and tightly linked RFLP markers were used to screen a BAC library of IRBB56, a resistant rice line con-taining the xa5 gene. A 213 kb contig covering the xa5 locus was constructed. According to the sequences from the Inter-national Rice Genome Sequening Project (IRGSP), the Chi-nese Superhybrid Rice Genome Project (SRGP) and some sub-clones of the contig, twelve SSLP and CAPS markers were developed for fine mapping. The xa5 gene was mapped to a 0.3 cM interval between markers K5 and T4, which spanned an interval of approximately 24 kb, co-segregating with marker T2. Sequence analysis of the 24 kb region re-vealed that an ABC transporter and a basal transcription factor (TFIIa) were potential candidates for the xa5 resis-tance gene product. The molecular mechanism by which the xa5 gene provides recessive, race-specific resistance to bacte-rial blight will be elucidated by the functional tests of the 24 kb DNA and the candidate genes.