Genetic diversity and relatedness of selected Iranian rice cultivars and disease resistance donors assayed by simple sequence repeats and candidate defense gene markers     

Ali Moumeni  Bahman Yazdi Samadi  Jianli Wu  Hei Leung 《Euphytica》2003,131(3):275-284

As a prerequisite to improving diseaseresistance and grain quality in Iranianrice cultivars, we determined the geneticrelatedness of popular local cultivars andblast-resistance donor germplasm usingfingerprints derived from simple sequencerepeat (SSR) and plant defense genemarkers. Fifty SSR markers and 28 defensecandidate genes were used to assess thegenetic diversity among popular ricecultivars from Iran and donors of blastresistance from breeding programs in Asia.Gene diversity estimate of the 16 corebreeding lines was 0.440 ± 0.028 basedon SSR markers. Genetic relationships amongthe cultivars were determined by clusteranalysis using SSR and candidate genedatasets. DNA fingerprints derived fromSSR and defense gene markers gave similargroupings of cultivars consistent withtheir genetic background: a) Iranian localvarieties, b) improved varieties in Iranplus donor indica germplasm from Asia, andc) japonica germplasm. Within-groupsimilarities for the traditional andimproved cultivars were greater than 80%and 75%, respectively. The traditional andimproved cultivars showed differentialreaction to blast pathogen isolates; alltraditional varieties were susceptible toblast pathogen isolates in Iran butresistant to isolates in the Philippines,whereas the improved varieties showedopposite reaction to pathogen isolates inIran and the Philippines. Both molecularand phenotypic data suggest a narrowgenetic basis in local and improvedcultivars in Iran and the need forincluding more diversity for the breedingprogram. The high degree of polymorphismobserved between local cultivars and donorsof blast resistance provide the neededinformation to follow the transmission ofresistance alleles from the donors inadvancing breeding lines.  相似文献   

Movements of the ricefield rat,Rattus argentiventer,near a trap-barrier system in rice crops in West Java,Indonesia     

P. R. Brown  L. K.-P. Leung  Sudarmaji  G. R. Singleton 《国际虫害防治杂志》2013,59(2):123-129

The movements of the ricefield rats ( Rattus argentiventer ) near a trap-barrier system (TBS) were assessed in lowland flood-irrigated rice crops in West Java, Indonesia, to test the hypothesis that a TBS with a 'trap-crop' modifies the movements of rats within 200 m from the trap-crop. The home range use and locations of rat burrows were assessed using radiotelemetry at two sites, one with a TBS with trap-crop (Treatment site, the crop inside the fence was planted 3 weeks earlier than the surrounding crop) and the other with a TBS without trap-crop (Control site, the crop inside the fence was planted at the same time as the surrounding crop). Each TBS was a 50 2 50 m plastic fence with eight multiple-capture rat traps set at the base. More than 700 rats were caught in the TBS with trap-crop, whereas only 10 rats were caught in the TBS without trap-crop. The home range size of females was significantly smaller at the Treatment site (0.96 ha) than the Control site (2.99 ha), but there was no difference for males. Seventy-eight per cent of rats caught in the TBS and fitted with radiocollars had their daytime burrow locations within 200 m of the TBS. We could not determine if the rats caught in the TBS were residents or transients according to demographic parameters. Our results support the hypothesis that a TBS with a trap-crop protects the surrounding rice crop out to a distance of at least 200 m.  相似文献   

Orientational ordering of polymers by atomic force microscope tip-surface interaction     

Leung OM  Goh MC 《Science (New York, N.Y.)》1992,255(5040):64-66

Results of studies on the interaction between the tip of an atomic force microscope and polystyrene molecules in a film spread on a surface are reported. The tip produces a persistent deformation on the film; some of the polymer molecules are eventually pulled up by the tip. Nanometer-size structures are induced, resulting in a pattern that is periodic and is oriented perpendicular to the scan direction.  相似文献   

Toward direct measurement of atmospheric nucleation     

Kulmala M  Riipinen I  Sipilä M  Manninen HE  Petäjä T  Junninen H  Maso MD  Mordas G  Mirme A  Vana M  Hirsikko A  Laakso L  Harrison RM  Hanson I  Leung C  Lehtinen KE  Kerminen VM 《Science (New York, N.Y.)》2007,318(5847):89-92

Atmospheric aerosol formation is known to occur almost all over the world, and the importance of these particles to climate and air quality has been recognized. Although almost all of the processes driving aerosol formation take place below a particle diameter of 3 nanometers, observations cover only larger particles. We introduce an instrumental setup to measure atmospheric concentrations of both neutral and charged nanometer-sized clusters. By applying the instruments in the field, we come to three important conclusions: (i) A pool of numerous neutral clusters in the sub-3 nanometer size range is continuously present; (ii) the processes initiating atmospheric aerosol formation start from particle sizes of approximately 1.5 nanometers; and (iii) neutral nucleation dominates over the ion-induced mechanism, at least in boreal forest conditions.  相似文献   

Genomics and agriculture. Collaborations in rice     

Fischer KS  Barton J  Khush GS  Leung H  Cantrell R 《Science (New York, N.Y.)》2000,290(5490):279-280

Advances in rice genomics will contribute to gene discovery and rice productivity, but many of the products with high potential for alleviating poverty and improving human nutrition may not be those that attract private investment. Although most genetic resources and biological expertise for functional genomics are in the public, many proprietary technologies are owned by the private sector. A public resource platform is needed for the application of genomic technology to accelerate gene discovery. We present a model and general principles in collaboration that can serve the poor and encourage innovation by both the public and private sectors.  相似文献   

Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions   总被引：2，自引：0，他引：2  

Riley S  Fraser C  Donnelly CA  Ghani AC  Abu-Raddad LJ  Hedley AJ  Leung GM  Ho LM  Lam TH  Thach TQ  Chau P  Chan KP  Lo SV  Leung PY  Tsang T  Ho W  Lee KH  Lau EM  Ferguson NM  Anderson RM 《Science (New York, N.Y.)》2003,300(5627):1961-1966

We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission.  相似文献   

Viability of OPS Vitrified Sheep Embryos After Direct Transfer     

RE Green  BFS Santos  CC Sicherle  FC Landim-Alvarenga  SD Bicudo 《Reproduction in domestic animals》2009,44(3):406-410

The aim of this study was to evaluate the viability in the effect of open pulled straw (OPS) vitrification procedure of sheep embryos after direct transference. Embryos were produced in vivo and cryopreserved in slow freezing or OPS vitrification. The survival rates of cryopreserved embryos were compared to non-frozen standard pattern. In a first set of experiments, embryos at morula and blastocyst stages were dived in ethylene glycol (1.5 M) and frozen in an automatic freezer. After being thawed, they were directly or indirectly transferred to ewes recipient. A second group of embryos were drawn into OPS and plunged into liquid nitrogen after being exposed at room temperature for 1 min and 45 s in 10% EG plus 10% dimethyl sulphoxide (DMSO), then again for 30 s in 20% EG + 20% DMSO + 0.5 M sucrose. After being warmed, embryos were also directly transferred using a French mini straw as the catheter for the transplantation process or after in vitro dilution of cryoprotectants (two-step-process). No significant difference was observed among fresh, frozen or vitrified embryos on pregnancy rate (50.0%, 38.6% and 55.8%). However, when we evaluated only the direct transference, the pregnancy rate of OPS vitrified embryos was higher than that of frozen embryos (57.1% vs 34.8%) (p = 0.07). In addition, vitrified morulae had a higher pregnancy rate than the one with frozen embryos (64.0% vs 38.9%) (p = 0.07). Finally, our results indicate that OPS vitrification technique in association with direct transference improves the viability of sheep embryos with potential applications to field conditions.  相似文献   

稻瘟病菌致病突变株的分离   总被引：4，自引：1，他引：3  

何月秋  唐文华 《云南农业大学学报(自然科学版)》2000,15(3):197-199

 利用4个分属宗亲群4,7,17 和44的菌株连续接种在C039的单基因近等基因系和基因累加系上, 以获得突变抗病基因新菌株。经13轮接种循环, 共分离到9个新菌株。其中8个针对C101LAC(Pi－1) 突变 , 另1个针对C101PKT (Pi－4a)和F128 (Pi－ta²) 的双位点突变。4个原始菌株, P06－6, 9248－6, 9239－4和101－7－2的突变频率分别为: 0, 2.82×10^－5, 2.05×10^－5 和9.09×10^－5。菌株针对不同抗病基因的突变频率不同,由Av－1变到Av－1^＋和由Avir－4a(t)突变到Av－4a^＋的频率分别为7.51×10^－5和6.14×10^－5。没有针对Pi－2突变体出现。  相似文献   

Drought Resistant Rice： an Integrated Crop Improvement Strategy     

Rice physiological sensitivity to drought  its impact on crop productivity in water-limited environments are well-documented 《分子植物育种》2007,5(2):211-212

Rice physiological sensitivity to drought and its impact on crop productivity in water-limited environments are well-documented （O＇Toole, 2004）. However, rice yields in drought-prone rainfed lowlands and most upland areas remain low and the current challenges are to reduce yield gaps observed between experimental plots and farmers＇ fields, and to increase rice water productivity to economic levels （Bennett, 2003; Pandey et al., 2007）. The unpredictability of drought and its inherent complexity have made it difficult to characterize component traits required for improved performance, hindering the breeding efforts to enhance drought resistance.  相似文献   

The OryzaSNP Project-SNP Discovery in Diverse Rice     

The OryzaSNP project 《分子植物育种》2007,5(2):246-247

The OryzaSNP project （http：//www.oryzasnp.org） is undertaking SNP discovery across the entire rice genome for 20 diverse varieties （McNally et al., 2006）. These varieties include representatives from the indica, tropical and temperate japonicas, aus, deepwater, and aromatic types of rice. SNPs are identified by array-based re-sequencing technology using very high-density oligomer arrays at Perlegen （Patil et al., 2001; Hinds et al., 2005）. SNPs arc called as those bases where hybridization of the target line differs from that of the Nipponbare reference genome. Release 4 of the Nipponbare sequence （The International Rice Genome Sequencing Project, 2005） was first masked for repetitive DNA, the segments remaining after masking were each blasted to the unmasked genome, and those that gave a single or a few hits were selected. After this filtering, 100 Mb of the rice genome is tiled onto arrays for SNP detection. Since long-range PCR is being used to prepare target DNA for hybridization, amplicons were chosen that span both unique sequence and TIGR gene models （Yuan et al., 2005） to define the final sequence for tiling. There is usually at least one LR-PCR amplicon in every 100 kb window. From this analysis,  相似文献