Rapid Population Analysis of Magnaporthe grisea by Using rep-PCR and Endogenous Repetitive DNA Sequences     

George ML  Nelson RJ  Zeigler RS  Leung H 《Phytopathology》1998,88(3):223-229

ABSTRACT DNA samples from Magnaporthe grisea isolates were fingerprinted by using repetitive element-based polymerase chain reaction (rep-PCR) with two outwardly directed primer sequences from Pot2, an element found in approximately 100 copies in the fungal genome. Variable length fragments, defining the sequences lying between these elements, were generated, and fingerprint patterns specific for individual strains were established. "Long PCR" conditions, including higher pH (9.2) and increased extension time (10 min) were used to amplify DNA fragments ranging from 400 bp to longer than 23 kb. Polymorphisms specific to M. grisea strains were generated, allowing inference of their genetic relationships. Segregation analysis was used to confirm single-locus inheritance for the fragments amplified by rep-PCR. Cluster analysis revealed robust groupings that corresponded to previously determined MGR586 restriction fragment length polymorphism lineages of the rice-infecting strains of the pathogen. We have also demonstrated the utility of rep-PCR to differentiate isolates that infect rice from those that infect nonrice hosts. DNA fingerprinting by Pot2 rep-PCR provides an efficient means to monitor the population dynamics of the blast pathogen. Because of the method's low cost and ease in application, it is now feasible to conduct large-scale population studies to understand the impact of host genotypes on pathogen evolution.  相似文献   

Detecting the non-breeding region and migration route of Whimbrels(Numenius phaeopus rogachevae)in the East Asian-Australasian Flyway     

Fenliang Kuang  Wei Wu  David Li  Chris J.Hassell  Grace Maglio  Kar-Sin K.Leung  Jonathan T.Coleman  Chuyu Cheng  Pavel S.Tomkovich  Zhijun Ma 《中国鸟类》2022,(1):72-77

Determining the migration routes and connections of migratory birds at the population level helps clarify intraspecific differences in migration.Five subspecies...  相似文献   

Application of the Neospora caninum IgG avidity ELISA in assessment of chronic reproductive losses after an outbreak of neosporosis in a herd of beef cattle.     

Camilla Bj?rkman  Milton M McAllister  Jenny Fr?ssling  Katarina N?slund  Felicia Leung  Arvid Uggla 《Journal of veterinary diagnostic investigation》2003,15(1):3-7

Point-source infections are most likely the cause for Neospora caninum-induced abortion outbreaks in cattle, whereas an increased annual abortion rate may be a consequence of vertical transmission. The aims of the present study were to examine the reproductive effects of neosporosis in a beef herd for 3 years, after a point-source outbreak and to use IgG avidity serology to examine the chronicity of infections and patterns of transmission. During the study, 76-78% of animals were seropositive for N. caninum. The pregnancy rate varied from 88% to 94%, without any reduction in the pregnancy rate of seropositive cows compared with seronegative cows. The annual abortion rate was 2.5-5.5%, and all but 1 abortion occurred in seropositive dams. The efficiency of vertical transmission was estimated to be 85%. Several calves, born to seronegative dams, were seropositive at 6-13 months of age, indicating a 22% mean annual rate of horizontal transmission. The mean avidity in seropositive cows increased from 30 during the initial outbreak to 74 after 3 years. The mode of IgG avidity was 21-40 during the initial abortion outbreak, 41-60 after 1 year, and 61-80 after 2 and 3 years. The results reveal high annual rates of both vertical and horizontal transmission of N. caninum in a herd of beef cows and provide further validation on the ability of the N. caninum IgG avidity ELISA to accurately assess the chronicity of infection.  相似文献   

Mapping of leaf and neck blast resistance genes with resistance gene analog, RAPD and RFLP in rice   总被引：17，自引：1，他引：17  

Jie-Yun Zhuang  Wen-Bin Ma  Jian-Li Wu  Rong-Yao Chai  Jun Lu  Ye-Yang Fan  Min-Zhong Jin  Hei Leung  Kang-Le Zheng 《Euphytica》2002,128(3):363-370

An F₈ recombinant inbred population was constructed using a commercial indica rice variety Zhong 156 as the female parent and a semidwarf indica variety Gumei 2 with durable resistance to rice blast as the male parent. Zhong 156 is resistant to the fungus race ZC₁₅ at the seedling stage but susceptible to the same race at the flowering stage. Gumei 2 is resistant to ZC₁₅ at both stages. The blast resistance of 148 recombinant inbred lines was evaluated using the blast race ZC₁₅. Genetic analysis indicated that the resistance to leaf blast was controlled by three genes and the presence of resistant alleles at any loci would result in resistance. One of the three genes did not have effects at the flowering stage. Two genes, tentatively assigned as Pi24(t) and Pi25(t), were mapped onto chromosome 12 and 6,respectively, based on RGA (resistance gene analog), RFLP and RAPD markers. Pi24(t) conferred resistance to leaf blast only, and its resistance allele was from Zhong 156. Pi25(t) conferred resistance to both leaf and neck blast, and its resistance allele was from Gumei 2. In a natural infection test in a blast hot-spot, Pi25(t) exhibited high resistance to neck blast, while Pi24(t) showed little effect. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Some Geographical Implications of the Revolution in Education in China     

C. K. Leung  T. N. Chiu 《Asia Pacific viewpoint》1974,15(1):51-60

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Solute redistribution during normal freezing     

Wei Keung  Solomon Leung  Gregory R. Carmichael 《Water, air, and soil pollution》1984,21(1-4):141-150

Mathematical models used in metallurgy to describe solute partitioning are applied to solute distribution in ice crystals. Results demonstrate that the model developed under the assumption of ideal directional freezing can be used to estimate distribution coefficients from experimental data. The deviation of experimental results from normal freezing theory is consistent with the Burton-Slichter film theory model.  相似文献   

The distribution and prevalence of Theileria buffeli in cattle in Queensland     

NP STEWART  NF STANDFAST†  FC BALDOCK‡  DJ REID  AJ de  VOS† 《Australian veterinary journal》1992,69(3):59-61

The distribution and prevalence of Thelleria buffeli in Queensland cattle were investigated using serum samples and blood films collected primarily for brucellosis surveillance and tick fever diagnosis. Serums from 8654 cattle from 357 farms throughout Queensland were examined by an indirect fluorescent antibody test for antibody to T buffeli. In addition, 347 peripheral blood films collected from 147 farms in south-eastern Queensland were examined for piroplasms of T buffeli. The overall herd and animal prevalences for T buffeli were 75% and 41%, respectively. There was significant variation among regions in both herd and animal prevalences (P less than 0.001). Herd and animal prevalences were highest in the north and east decreasing westward. The results indicate that T buffeli is more widespread in Queensland than previously thought.  相似文献   

籼稻品种三黄占2号的稻瘟病持久抗性评价与遗传分析   总被引：13，自引：0，他引：13  

伍尚忠  朱小源  刘斌  杨祁云  张少红  H.Leung 《中国农业科学》2004,37(4):528-528

 籼稻三黄占2号在生产上种植10多年,表现了稳定持久的稻瘟病抗性。接种及多点田间试验结果表明,三黄占2号不仅对中国稻瘟病菌株有广谱抗性,而且对菲律宾稻瘟病菌株亦有高的抗性频率(98%)。在国际稻瘟病圃(IRBN)其叶瘟及穗瘟抗性相当或好于持久抗性品种OS6、Moroberekan和IR36。三黄占2号感病后,亦显示出高水平稻瘟病数量抗性。分析由三黄占2号与丽江新团黑谷杂交构建的重组自交系分离群体的抗病性,发现三黄占2号稻瘟病质量抗性是由多个主效基因控制的,其稻瘟病数量抗性是非小种专一的。应用候选抗性基因方法鉴  相似文献   

Pro-bone and antifat effects of green tea and its polyphenol, epigallocatechin, in rat mesenchymal stem cells in vitro     

Ko CH  Siu WS  Wong HL  Shum WT  Fung KP  San Lau CB  Leung PC 《Journal of agricultural and food chemistry》2011,59(18):9870-9876

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Chemical and genetic assessment of variability in commercial Radix Astragali (Astragalus spp.) by ion trap LC-MS and nuclear ribosomal DNA barcoding sequence analyses     

Xiao WL  Motley TJ  Unachukwu UJ  Lau CB  Jiang B  Hong F  Leung PC  Wang QF  Livingston PO  Cassileth BR  Kennelly EJ 《Journal of agricultural and food chemistry》2011,59(5):1548-1556

Radix Astragali (Huangqi) has been demonstrated to have a wide range of immunopotentiating effects and has been used as an adjuvant medicine during cancer therapy. Identity issues in the collection of Radix Astragali exist because many sympatric species of Astragalus occur in the northern regions of China. In order to assess the quality, purity, and uniformity of commercial Radix Astragali, 44 samples were purchased from herbal stores in Hong Kong and New York City. The main constituents, including four isoflavonoids and three saponins, were quantitatively determined by liquid chromatography mass spectrometry (LC-MS). There was significant sample-to-sample variability in the amounts of the saponins and isoflavonoids measured. Furthermore, DNA barcoding utilizing the variable nuclear ITS spacer regions of the 44 purchased Radix Astragali samples were sequenced, aligned and compared. Eight polymorphic point mutations were identified which separated the Radix Astragali samples into three groups. These results indicate that the chemical and genetic variability that exists among Radix Astragali medicinal products is still a consistency and quality issue for this herbal. Two-way ANOVA analysis showed significant effects on the contents of the seven tested compounds when both phylogenetic and geographic (i.e., point of purchase) factors were considered. Therefore, chemical profiles determined by LC-MS and DNA profiles in ITS spacer domains could serve as barcode markers for quality control of Radix Astragali.  相似文献