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We amplified resistance gene analogues (RGAs) from the genomic DNA of 10 rice lines having varying degree of resistance to Magnaporthe grisea by using degenerate primers and various RGAs were mapped in silico on different rice chromosomes. The amplified products were grouped into 3–8 restriction fragment length polymorphic classes by using Mbo1 and Alu1 restriction enzymes. Of 98 RGAs obtained in this study, 65 RGA clones showed more than 95% homology with various RGAs sequences present in the GenBank. Phylogenetic analysis of these RGAs formed 11 groups. Using sequence homology approach, RGAs isolated in this study were physically mapped on 23 loci on chromosomes 1, 2, 3, 4, 5, 6, 7, 8, 10, 11 and 12. Twenty RGAs were mapped near to the chromosomal regions containing known genes/QTLs for rice blast, bacterial leaf blight and sheath blight resistance. Thirty‐nine RGA sequences also contained open reading frame representing signature of potential disease resistance genes. 相似文献
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RFLP mapping of isozymes,RAPD and QTLs for grain shape,brown planthopper resistance in a doubled haploid rice population 总被引:17,自引:0,他引:17
Huang Ning Parco Arnold Mew Teresita Magpantay Gerard McCouch Susan Guiderdoni Emmanuel Xu Jichen Subudhi Prasanta Angeles Enrique R. Khush Gurdev S. 《Molecular breeding : new strategies in plant improvement》1997,3(2):105-113
We have developed an RFLP framework map with 146 RFLP markers based on a doubled haploid population derived from a cross between an indica variety IR64 and a japonica variety Azucena. The population carries 50.2% of IR64 loci and 49.8% of Azucena loci, indicating an equal amount of genetic materials from each parent has been transmitted to the progenies through anther culture. However, some markers show segregation distortion. These distorted marker loci are located on 10 chromosomal segments. Using this map we were able to place 8 isozymes, 14 RAPDs, 12 cloned genes, 1 gene for brown planthopper (BPH) resistance, and 12 QTLs for grain length, grain width and length/width ratio onto rice chromosomes. The major gene for BPH resistance was mapped on chromosome 12 near RG463 and isozyme Sdh-1. Most of the QTLs identified for the three grain characters were closely linked on chromosomes 1, 2, 3 and 10. We concluded that the RFLP framework map presented here will be useful for mapping other genes segregating in this doubled haploid population. Thus rapid generation of doubled haploid lines and their unbiased segregation make it very attractive for gene mapping. 相似文献
4.
Alien introgression in rice 总被引:41,自引:0,他引:41
Rice (Oryza sativa L.) productivity is affected by several biotic and abiotic stresses. The genetic variability for some of these stresses is limited in the cultivated rice germplasm. Moreover, changes in insect biotypes and disease races are a continuing threat to increased rice production. There is thus an urgent need to broaden the rice gene pool by introgressing genes for such traits from diverse sources. The wild species of Oryza representing AA, BB, CC, BBCC, CCDD, EE, FF, GG and HHJJ genomes are an important reservoir of useful genes. However, low crossability and limited recombination between chromosomes of cultivated and wild species limit the transfer of such genes. At IRRI, a series of hybrids and monosomic alien addition lines have been produced through embryo rescue following hybridization between rice and several distantly related species. Cytoplasmic male sterility and genes for resistance to grassy stunt virus and bacterial blight have been transferred from A genome wild species into rice. Similarly, genes for resistance to brown planthopper, bacterial blight and blast have also been introgressed across crossability barriers from distanly related species into rice. Some of the introgressed genes have been mapped via linkage to molecular markers. One of the genes Xa-21 introgressed from O. longistaminata has been cloned and physically mapped on chromosome 11 of rice using BAC library and flourescence in-situ hybridization. RFLP analysis revealed introgression from 11 of the 12 chromosomes of C genome species into rice. Introgression has also been obtained from other distant genomes (EE, FF, GG) into rice and in majority of the cases one or two RFLP markers were introgressed. Reciprocal replacement of RFLP alleles of wild species with the alleles of O. sativa indicates alien gene transfer through crossing over. The rapid recovery of recurrent phenotypes in BC2 and BC3 generations from wide crosses is an indication of limited recombination. Further cytogenetic and molecular investigations are required to determine precisely the mechanism of introgression of small chromosome segments from distant genomes in the face of limited homoeologous chromosome pairing. Future research should focus on enhancing recombination between homoeologous chromosomes. Introgression of QTL from wild species should be attempted to increase the yield potential of rice. 相似文献
5.
Barley disease resistance gene analogs of the NBS-LRR class: identification and mapping 总被引:11,自引:0,他引:11
Madsen LH Collins NC Rakwalska M Backes G Sandal N Krusell L Jensen J Waterman EH Jahoor A Ayliffe M Pryor AJ Langridge P Schulze-Lefert P Stougaard J 《Molecular genetics and genomics : MGG》2003,269(1):150-161
The majority of verified plant disease resistance genes isolated to date are of the NBS-LRR class, encoding proteins with a predicted nucleotide binding site (NBS) and a leucine-rich repeat (LRR) region. We took advantage of the sequence conservation in the NBS motif to clone, by PCR, gene fragments from barley representing putative disease resistance genes of this class. Over 30 different resistance gene analogs (RGAs) were isolated from the barley cultivar Regatta. These were grouped into 13 classes based on DNA sequence similarity. Actively transcribed genes were identified from all classes but one, and cDNA clones were isolated to derive the complete NBS-LRR protein sequences. Some of the NBS-LRR genes exhibited variation with respect to whether and where particular introns were spliced, as well as frequent premature polyadenylation. DNA sequences related to the majority of the barley RGAs were identified in the recently expanded public rice genomic sequence database, indicating that the rice sequence can be used to extract a large proportion of the RGAs from barley and other cereals. Using a combination of RFLP and PCR marker techniques, representatives of all barley RGA gene classes were mapped in the barley genome, to all chromosomes except 4H. A number of the RGA loci map in the vicinity of known disease resistance loci, and the association between RGA S-120 and the nematode resistance locus Ha2 on chromosome 2H was further tested by co-segregation analysis. Most of the RGA sequences reported here have not been described previously, and represent a useful resource as candidates or molecular markers for disease resistance genes in barley and other cereals. 相似文献
6.
Irfan A. Ghazi Prem S. Srivastava Vivek Dalal Kishor Gaikwad Ashok K. Singh Tilak R. Sharma Nagendra K. Singh Trilochan Mohapatra 《Journal of biosciences》2009,34(2):251-261
Rice is the first cereal genome with a finished sequence and a model crop that has important syntenic relationships with other
cereal species. The objectives of our study were to identify resistance gene analogue (RGA) sequences from chromosome 11 of
rice, understand their expression in other cereals and dicots by in silico analysis, determine their presence on other rice chromosomes, and evaluate the extent of polymorphism and actual expression
in a set of rice genotypes. A total of 195 RGAs were predicted and physically localised. Of these, 91.79% expressed in rice,
and 51.28% expressed in wheat, which was the highest among other cereals. Among monocots, sugarcane showed the highest (78.92%)
expression, while among dicots, RGAs were maximally expressed in Arabidopsis (11.79%). Interestingly, two of the chromosome 11-specific RGAs were found to be expressing in all the organisms studied.
Eighty RGAs of chromosome 11 had significant homology with chromosome 12, which was the maximum among all the rice chromosomes.
Thirty-one per cent of the RGAs used in polymerase chain reaction (PCR) amplification showed polymorphism in a set of rice
genotypes. Actual gene expression analysis revealed post-inoculation induction of one RGA in the rice line IRBB-4 carrying
the bacterial blight resistance gene Xa-4. Our results have implications for the development of sequence-based markers and functional validation of specific RGAs in
rice.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.
Supplementary tables pertaining to this article are available on the Journal of Biosciences Website at 相似文献
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Phinyarat Kongprakhon Alfonso Cuesta‐Marcos Patrick M. Hayes Vipa Hongtrakul Pattama Sirithunya Theerayuth Toojinda Nitsri Sangduen 《Journal of Phytopathology》2010,158(2):125-131
Pyricularia grisea is the most destructive and cosmopolitan fungal pathogen of rice and it can also cause disease on other agriculturally important cereals. We determined the number, location and interaction of quantitative trait loci (QTL) associated with resistance to P. grisea isolates obtained from rice (THL142 and THL222) and barley (TH16 and THL80) grown in Thailand. The isolates showed a spectrum of virulence when used to inoculate a series of differentials. We used a reference blast resistance mapping population of rice (IR64 × Azucena). IR64 was highly resistant, and Azucena was highly susceptible, to all four isolates. The numbers of resistant vs. susceptible progeny suggest that the resistance of IR64 is determined by two or three genes with additive effects. The correlation coefficients for all pairwise comparisons of disease severity were high and highest between barley isolates and between rice isolates. Four QTL were detected, one on each of the following chromosomes 2, 8, 9 and 10. IR64 contributed resistance alleles at three of the QTL (chromosomes 2, 8 and 9). Azucena contributed the resistance allele at the QTL on chromosome 10 in response to inoculation with isolate THL142. The results of the QTL analysis support interpretation of the phenotypic frequency distributions regarding the number of genes determining resistance to the four isolates in this population. Our results are novel in adding blast isolates from barley to the catalogue of pathogen specificities to which a gene, or genes, from IR64 confer resistance. 相似文献
9.
QTL analysis and mapping of pi21, a recessive gene for field resistance to rice blast in Japanese upland rice 总被引:14,自引:0,他引:14
S. Fukuoka K. Okuno 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(2-3):185-190
Field resistance is defined as the resistance that allows effective control of a parasite under natural field conditions and
is durable when exposed to new races of that parasite. To identify the genes for field resistance to rice blast, quantitative
trait loci (QTLs) conferring field resistance to rice blast in Japanese upland rice were detected and mapped using RFLP and
SSR markers. QTL analysis was carried out in F4 progeny lines from the cross between Nipponbare (moderately susceptible, lowland) and Owarihatamochi (resistant, upland).
Two QTLs were detected on chromosome 4 and one QTL was detected on each of chromosomes 9 and 12. The phenotypic variation
explained by each QTL ranged from 7.9 to 45.7% and the four QTLs explained 66.3% of the total phenotypic variation. Backcrossed
progeny lines were developed to transfer the QTL with largest effect using the susceptible cultivar Aichiasahi as a recurrent
parent. Among 82 F3 lines derived from the backcross, resistance segregated in the expected ratio of resistant 1 : heterozygous 2 : susceptible
1. The average score for blast resistance measured in the field was 4.2 ± 0.67, 7.5 ± 0.51and 8.2 ± 0.66, for resistant, heterozygous
and susceptible groups, respectively. The resistance gene, designated pi21, was mapped on chromosome 4 as a single recessive gene between RFLP marker loci G271 and G317 at a distance of 5.0 cM and 8.5 cM, respectively. The relationship to previously reported major genes and QTLs conferring
resistance to blasts, and the significance of marker-assisted selection to improve field resistance, are discussed.
Received: 8 June 2000 / Accepted: 24 November 2000 相似文献
10.
K. K. Jena G. Kochert G. S. Khush 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1992,84(5-6):608-616
Summary Fifty-two introgression lines (BC2F8) from crosses between two Oryza sativa parents and five accessions of O. officinalis were analyzed for the introgression of O. officinalis chromosome segments. DNA from the parents and introgression lines was analyzed with 177 RFLP markers located at approximately 10-cM intervals over the rice chromosomes. Most probe/enzyme combinations detected RFLPs between the parents. Of the 174 informative markers, 28 identified putative O. officinalis introgressed chromosome segments in 1 or more of the introgression lines. Introgressed segments were found on 11 of the 12 rice chromosomes. In most cases of introgression, O. sativa RFLP alleles were replaced by O. officinalis alleles. Introgressed segments were very small in size and similar in plants derived from early and later generations. Some nonconventional recombination mechanism may be involved in the transfer of such small chromosomal segments from O. officinalis chromosomes to those of O. sativa. Some of the introgressed segments show association with genes for brown planthopper (BPH) resistance in some introgressed lines, but not in others. Thus, none of the RFLP markers could be unambiguously associated with BPH resistance. 相似文献
11.
Mapping of the QTL (quantitative trait locus) conferring partial resistance to leaf blast in rice cultivar Chubu 32 总被引:7,自引:0,他引:7
Zenbayashi K Ashizawa T Tani T Koizumi S 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,104(4):547-552
The rice cultivar Chubu 32 possesses a high level of partial resistance to leaf blast. The number and chromosomal location
of genes conferring this resistance were detected by restriction fragment length polymorphism (RFLP) linkage mapping and quantitative
trait locus (QTL) analysis. For the mapping, 149 F3 lines derived from the cross between rice cultivar Norin 29, with a low level of partial resistance, and Chubu 32 were used,
and their partial resistance to leaf blast was assessed in upland nurseries. A linkage map covering six chromosomes and consisting
of 36 RFLP markers was constructed. In the map, only one significant QTL (LOD>2.0) for partial resistance was detected on
chromosome 11. This QTL explained 45.6% of the phenotypic variation. The segregation ratio of the F3 lines was 3:1 for partial
resistance to susceptibility. These results suggest that the partial resistance in Chubu 32 is controlled by a major gene.
Received: 15 March 2001 / Accepted: 13 August 2001 相似文献
12.
Mapping QTLs for field resistance to the rice blast pathogen and evaluating their individual and combined utility in improved varieties 总被引:2,自引:0,他引:2
Tabien E Li Z Paterson H Marchetti A Stansel W Pinson M 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,105(2-3):313-324
Lines from a Lemont x Teqing recombinant inbred population were evaluated for dilatory resistance to rice blast disease using: (1) the Standard Evaluation System (SES) for rating leaf blast, (2) the percentage diseased leaf area (%DLA), and (3) the area under a disease progress curve (AUDPC). RFLP mapping using 175 well-distributed loci revealed nine QTLs, one each on chromosomes 1, 2, 3, 4, 6, 7 and 9, with two loci on chromosome 12. All nine putative QTLs were associated with AUDPC, six with both a %DLA and a SES rating. Teqing contributed the resistance allele for all these loci except for the one located on chromosome 4. Individual QTLs accounted for 5-32% of the observed phenotypic variation, and combined QTL models accounted for 43-53%. Three QTLs were located near three of the four major resistance genes previously identified in this population. The resistances of both Lemont and Teqing were attributable to a combination of both major genes capable of inducing hypersensitive reactions and minor genes causing less-distinctive phenotypic differences. Interactions were noted between QTLs and major genes. Our findings are in support of the strategy of pyramiding major genes and QTLs in carefully selected combinations to develop improved varieties with resistance to the blast fungus that is both broad in spectrum and durable. 相似文献
13.
Bingsong Zheng Ling Yang Chuanzao Mao Youjun Huang Ping Wu 《遗传学报》2008,35(8):473-484
The variation of seedling characteristics under different water supply conditions is strongly associated with drought resistance in rice (Oryza sativa L.) and a better elucidation of its genetics is helpful for improving rice drought resistance. Ninety-six doubled-haploid (DH)rice lines of an indica and japonica cross were grown in both flooding and upland conditions and QTLs for morphological traits at seedling stage were examined using 208 restriction fragment length polymorphism (RFLP) and 76 microsatellite (SSR) markers. A total of 32 putative QTLs were associated with the four seedling traits: average of three adventitious root lengths (ARL), shoot height (SH), shoot biomass (SW), and root to shoot dry weight ratio (RSR). Five QTLs detected were the same under control and upland conditions. The ratio between the mean value of the seedling trait under upland and flooding conditions was used for assessing drought tolerance. A total of six QTLs for drought tolerance were detected. Comparative analysis was performed for the QTLs detected in this case and those reported from two other populations with the same upland rice variety Azucena as parent. Several identical QTLs for seedling elongation across the three populations with the positive alleles from the upland rice Azucena were detected, which suggests that the alleles of Azucena might be involved in water stress-accelerated elongation of rice under different genetic backgrounds. Five cell wall-related candidate genes for OsEXP1, OsEXP2, OsEXP4, EXT, and EGase were mapped on the intervals carrying the QTLs for seedling traits. 相似文献
14.
Genomic distribution and characterization of EST-derived resistance gene analogs (RGAs) in sugarcane 总被引:9,自引:0,他引:9
Rossi M Araujo PG Paulet F Garsmeur O Dias VM Chen H Van Sluys MA D'Hont A 《Molecular genetics and genomics : MGG》2003,269(3):406-419
A large sugarcane EST (expressed sequence tag) project recently gave us access to 261,609 EST sequences from sugarcane, assembled into 81,223 clusters. Among these, we identified 88 resistance gene analogs (RGAs) based on their homology to typical pathogen resistance genes, using a stringent BLAST search with a threshold e-value of e(-50). They included representatives of the three major groups of resistance genes with NBS/LRR, LRR or S/T KINASE domains. Fifty RGAs showed a total of 148 single-dose polymorphic RFLP markers, which could be located on the sugarcane reference genetic map (constructed in cultivar R570, 2n=approximately 115). Fifty-five SSR loci corresponding to 134 markers in R570 were also mapped to enable the classification of the various haplotypes into homology groups. Several RGA clusters were found. One cluster of two LRR-like loci mapped close to the only disease resistance gene known so far in sugarcane, which confers resistance to common rust. Detailed sequence comparison between two NBS/LRR RGA clusters in relation to their orthologs in rice and maize suggests their polyphyletic origins, and indicates that the degree of divergence between paralogous RGAs in sugarcane can be larger than that from an ortholog in a distant species. 相似文献
15.
Huettel B Santra D Muehlbauer J Kahl G 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2002,105(2-3):479-490
Resistance gene analogues (RGAs) of Cicer were isolated by different PCR approaches and mapped in an inter-specific cross segregating for fusarium wilt by RFLP and CAPS analysis. Initially, two pairs of degenerate primers targeting sequences encoded at nucleotide-binding sites (NBS), which are conserved in plant disease resistance genes such as RPS2, L6 and N, were selected for amplification. Cloning and sequence analysis of amplified products from C. arietinum DNA revealed eight different RGAs. Additionally, five RGAs were identified after characterisation of the presumptive RGA alleles from C. reticulatum. Therefore, a total of 13 different RGAs were isolated from Cicer and classified through pair-wise comparison into nine distinct classes with sequence similarities below a 68% amino acid identity threshold. Sequence comparison of seven RGA alleles of C. arietinum and C. reticulatum revealed polymorphisms in four RGAs with identical numbers of synonymous and non-synonymous substitutions. An NlaIII site, unique in the RGA-A allele of C. arietinum, was exploited for CAPS analysis. Genomic organisation and map position of the NBS-LRR candidate resistance genes was probed by RFLP analysis. Both single-copy as well as multi-copy sequence families were present for the selected RGAs, which represented eight different classes. Five RGAs were mapped in an inter-specific population segregating for three race-specific Fusarium resistances. All RGAs mapped to four of the previously established eight linkage groups for chickpea. Two NBS-LRR clusters were identified that could not be resolved in our mapping population. One of these clusters, which is characterised by RFLP probe CaRGA-D, mapped to the linkage group harbouring two of three Fusarium resistance genes characterised in the inter-specific population. Our study provides a starting point for the characterisation and genetic mapping of candidate resistance genes in Cicer that is useful for marker-assisted selection and as a pool for resistance genes of Cicer. 相似文献
16.
C L McIntyre R E Casu J Drenth D Knight V A Whan B J Croft D R Jordan J M Manners 《Génome》2005,48(3):391-400
Fifty-four different sugarcane resistance gene analogue (RGA) sequences were isolated, characterized, and used to identify molecular markers linked to major disease-resistance loci in sugarcane. Ten RGAs were identified from a sugarcane stem expressed sequence tag (EST) library; the remaining 44 were isolated from sugarcane stem, leaf, and root tissue using primers designed to conserved RGA motifs. The map location of 31 of the RGAs was determined in sugarcane and compared with the location of quantitative trait loci (QTL) for brown rust resistance. After 2 years of phenotyping, 3 RGAs were shown to generate markers that were significantly associated with resistance to this disease. To assist in the understanding of the complex genetic structure of sugarcane, 17 of the 31 RGAs were also mapped in sorghum. Comparative mapping between sugarcane and sorghum revealed syntenic localization of several RGA clusters. The 3 brown rust associated RGAs were shown to map to the same linkage group (LG) in sorghum with 2 mapping to one region and the third to a region previously shown to contain a major rust-resistance QTL in sorghum. These results illustrate the value of using RGAs for the identification of markers linked to disease resistance loci and the value of simultaneous mapping in sugarcane and sorghum. 相似文献
17.
Identification of five new blast resistance genes in the highly blast-resistant rice variety IR64 using a QTL mapping strategy 总被引:12,自引:0,他引:12
Sallaud C Lorieux M Roumen E Tharreau D Berruyer R Svestasrani P Garsmeur O Ghesquiere A Notteghem JL 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2003,106(5):794-803
Rice progenies used for the construction of genetic maps permit exhaustive identification and characterization of resistance genes present in their parental cultivars. We inoculated a rice progeny derived from the cross IR64 x Azucena with different Magnaporthe grisea isolates that showed differential responses on the parental cultivars. By QTL mapping, nine unlinked loci conferring resistance to each isolate were identified and named Pi-24( t) to Pi-32( t). They could correspond to nine specific resistance genes. Five of these resistance loci (RLs) were mapped at chromosomal locations where no resistance gene was previously reported, defining new resistance genes. Using degenerate primers of the NBS (nucleotide binding site) motif found in many resistance genes, two resistance gene analogues (RGAs) IR86 and IR14 were identified and mapped closely to two blast RLs (resistance identified in this study, i.e. Pi-29(t) and Pi-30(t) respectively). These two RLs may correspond to the Pi-11 and Pi-a blast resistance genes previously identified. Moreover, the ir86 and ir14 genes have been identified "in silico" on the indica rice cultivar 93-11, recently sequenced by Chinese researchers. Both genes encodes NBS-LRR-like proteins that are characteristics of plant-disease resistance genes. 相似文献
18.
Quantitative disease resistance conferred by quantitative trait loci (QTLs) is presumably of wider spectrum and durable. Forty-four cDNA clones, representing 44 defense-responsive genes, were fine mapped to 56 loci distributed on 9 of the 12 rice chromosomes. The locations of 32 loci detected by 27 cDNA clones were associated with previously identified resistance QTLs for different rice diseases, including blast, bacterial blight, sheath blight and yellow mottle virus. The loci detected by the same multiple-copy cDNA clones were frequently located on similar locations of different chromosomes. Some of the multiple loci detected by the same clones were all associated with resistance QTLs. These results suggest that some of the genes may be important components in regulation of defense responses against pathogen invasion and they may be the candidates for studying the mechanism of quantitative disease resistance in rice. 相似文献
19.
Resistance gene analogues from rice: cloning, sequencing and mapping 总被引:18,自引:0,他引:18
R. Mago S. Nair M. Mohan 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,99(1-2):50-57
Degenerate oligonucleotide primers were designed on the basis of nucleotide-binding-site (NBS) motifs conserved between resistance
genes of Arabidopsis, flax and tobacco and subsequently used as PCR primers to amplify resistance gene analogues (RGA) in rice. Primers amplified
a major band of approximately 500 bp. Restriction analysis of the amplified product revealed that the band was made up of
several different fragments. Many of these fragments were cloned. Sixty different cloned fragments were analysed and assigned
to 14 categories based on Southern blot analysis. Fourteen clones, each representing one of the 14 categories of RGAs were
mapped onto the rice genetic map using a Nipponbare ( japonica)בKasalath’ (indica) mapping population consisting of 186 F2 lines. Of the 14 clones representing each class 12 could be mapped onto five different chromosomes of rice with a major cluster
of 8 RGAs on chromosome 11. Our results indicate that it is possible to use sequence homology from conserved motifs of known
resistance genes to amplify candidate resistance genes from diverse plant taxa.
Received: 23 September 1998 / Accepted: 28 November 1998 相似文献
20.
Quantitative disease resistance conferred by quantitative trait loci (QTLs) is presumably of wider spectrum and durable. Forty-four cDNA clones, representing 44 defense-responsive genes, were fine mapped to 56 loci distributed on 9 of the 12 rice chromosomes. The locations of 32 loci detected by 27 cDNA clones were associated with previously identified resistance QTLs for different rice diseases, including blast, bacterial blight, sheath blight and yellow mottle virus. The loci detected by the same multiple-copy cDNA clones were frequently located on similar locations of different chromosomes. Some of the multiple loci detected by the same clones were all associated with resistance QTLs. These results suggest that some of the genes may be important components in regulation of defense responses against pathogen invasion and they may be the candidates for studying the mechanism of quantitative disease resistance in rice. 相似文献