| Brown planthopper (Nilaparvata lugens Stal., BPH) is one of the most serious insect pests to rice. Planting of rice varieties with BPH resistance can prevent BPH bursting out and damage. Mapping and cloning of BPH resistance genes of rice can not only provide new genes for molecular breeding, but also help elucidating the biological basis for resistance, adding new ingredients into the study of plant resistance mechanism.Rice line B5, showing high resistance to BPH, was introgressed from the highly resistant wild rice, Oryza officinalis Wall ex Watt, by hybridizing with cultivated rice. We have previously mapped two QTLs for BPH resistance in B5, namely Qbpl and Qbp2 onto R1925-G1318 region of chromosome 3 and R288-C820 region of chromosome 4, respectively. And some interactions have been detected between these two loci.In order to clone the BPH resistance genes in B5, we have constructed a genomic library of B5 in binary vector pCLD04541. This library contains 36,864 clones with an average insert length of 60 kb, covering 5.1 times haploid rice genome. Randomly picked 100 clones from this library show no fingerprinting changes after 5 days' successive culture, which showed that the clones in the library were stable. Binary vector pCLD04541 can be used directly for plantIVchanges after 5 days' successive culture, which showed that the clones in the library were stable. Binary vector pCLD04541 can be used directly for plant transformation, once the clone containing the candidate BPH resistance gene had been identified, it can be transformed into the receptor plant directly, thus the process for map-based cloning of BPH resistance gene from rice can be streamlined.Qbpl locates on R1925-G1318 region of chromosome 3, according to the Rice Genome Project (RGP: http://rgp.dna.affrc.go.jp), the physical length of this region is about 200 kb. Four clones OSJNBa0054C6, OSJNBa0032Gll, OSJNBa0069Bll and OSJNBa0078C23 from the Nipponbare library can totally cover this region by overlapping. Using restriction enzyme-digested product of these four clones and RFLP markers in this region as probes, we picked out the B5 library clones in this region and ascertained the overlapping relationship among them by fingerprinting and Sourthern analysis. A contig containing 11 clones was constructed from B5 library and the till-path was 5 clones.According to the RGP, the 200 kb fragment in the R1925-G1318 region codes for about 40 genes. At present, since there are only few insect resistant genes cloned, it is still difficult to select the candidate BPH resistant gene from 40 candidates, giving prominence to the necessary to fine map Qbpl.In the process of fine-mapping single locus of the QTLs, in order to remove the influence of other loci, it is a routine practice to construct near isogenic lines. According to this idea, we selected resistant lines from the MH63/B5 recombinant inbreeding lines, and constructed backcrossing population for Qbpl and Qbp2, respectively. In this process, molecular marker assisted method was used. The line used to construct the backcrossing population for Qbpl had the same band-type asvthe resistant parent B5 at R1925 and G1318, and at R288 and C820 the same band-type as the susceptible parent MH63, so that Qbpl, removing the influence of Qbp2, provides resistance. Two backcrossing populations for Qbpl were constructed, each coming from a resistant line.Using two markers MRG2684 and RM570, which are much farer from Qbpl than R1925 and G1318, we firstly selected recombinant individuals from the backcrossing populations of Qbpl. Fifty-nine individuals were selected from 1580 ones in one population, and in the other population 81 individuals were selected from 1992 ones. From the sequence of the RGP, we designed 4 polymorphic SSR markers in this region. Also, a 0.5 kb RFLP marker 7S was cloned as a genomic fragment from the B5 library clone 76B10, showing polymorphism between parents B5 and MH63. Using these newly developed markers, we analyzed the genotypes of the recombinant individuals in R1...
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