共查询到20条相似文献,搜索用时 31 毫秒
1.
A total of 8579 Salmonella strains received during 1973–1982 were tested for their antibiogram patterns against nine routinely used antibiotics including gentamicin. Of these, 380 strains (4.4%) showed resistance to gentamicin at levels of 10 g/ml and above. A high degree of resistance to gentamicin was recorded in 1979 (18.7%) and 1980 (9.4%). M.I.C. levels of strains received during 1982 were determined and it was found that some strains had levels as high as 160 g/ml. The comparative results of gentamicin resistance from 1973 to 1982 are presented and the public health significance of the alarming increase in two years (1979–1980) is discussed. 相似文献
2.
3.
4.
S. Paillard I. Goldringer J. Enjalbert G. Doussinault C. de Vallavieille-Pope P. Brabant 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2000,101(3):449-456
Dynamic management has been proposed as a complementary strategy to gene banks for the conservation of genetic resources.
The evolution of frequencies of genes for specific resistance towards powdery mildew (caused by Blumeria graminis f. sp. tritici) in populations of a French network for dynamic management of bread wheat genetic resources was investigated after 10 years
of multiplication without human selection. The objective was to determine whether specific resistance gene diversity was maintained
in the populations and whether any changes could be attributed to selection due to pathogen pressure. Seven populations, originating
from four of the network sites, were characterized and compared to the initial population for six specific resistance gene
frequencies detected by nine Blumeria graminis f. sp. tritici isolates. Diversity decreased at the population level, but because of a strong differentiation between the populations, this
diversity was maintained at the network level. The comparison of Fst parameters estimated on neutral markers (RFLP) and on resistance gene data revealed that in two of the populations specific
resistance genes had been selected by pathogen pressure, whereas evolution in two other populations seemed to be the result
of genetic drift. For the three last populations, conclusions were less clear, as one had probably experienced a strong bottleneck
and the other two presented intermediate Fst values. A dynamic management network with sites contrasted for pathogen pressure, allowing genetic drift in some populations
and selection in others, appeared, at least on the short term, to be a good tool for maintaining the diversity of genes for
specific resistance to powdery mildew.
Received: 15 December 1999 / Accepted: 30 December 1999 相似文献
5.
Lin F Xue SL Zhang ZZ Zhang CQ Kong ZX Yao GQ Tian DG Zhu HL Li CJ Cao Y Wei JB Luo QY Ma ZQ 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2006,112(3):528-535
Fusarium head blight (FHB) is a serious disease in wheat and barley affecting both yield and quality. To identify genes for
resistance to infection, the RIL population derived from ‘Nanda2419’ × ‘Wangshuibai’ and the parents were evaluated for percentage
of infected spikes (PIS) in four different environments. Using a 2,960 cM marker framework map constructed for this population,
ten chromosome regions were detected for their association with type I resistance through interval mapping with Mapmaker/QTL,
among which QTLs mapped in the intervals of Xwmc349~Xgwm149 on chromosome 4B, of Xwmc96~Xgwm304 on chromosome 5A and of Xgwm408~Xbarc140 on chromosome 5B were revealed in at least three environments and have Wangshuibai as the source of resistance alleles. Qfhi.nau-4B and Qfhi.nau-5A had larger effects and explained up to 17.5 and 27.0% of the phenotypic variance, respectively. To detect epistasis QTLs,
two-locus interactions were examined by whole genome scan. Interactions of five locus pairs were found to have significant
effects on type I resistance with the LOD score ranging 3.8–6.5 and four of them conferred resistance in parental phase. The
one with the most significant effect was Xcfd42~Xgwm469 (6D)/Xwmc390-2~Xbd04 (2A) pair. No QTL × E interaction was detected for PIS. It was found that flowering time did not have significant effects
on PIS in this population. Our studies indicated that Wangshuibai is useful for breeding for both type I and type II scab
resistance and the markers associated with the QTLs could be used in marker-assisted selection and isolation of scab-resistance
QTLs.
F. Lin and S.L. Xue equally contributed to this article 相似文献
6.
7.
8.
Z. V. Vulkova V. G. Sotirova 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1993,87(3):337-342
L. peruvianum var humifusum is reproductively the most isolated of the species of the genusLycopersicon. It can be crossed with the cultivated tomato usingL. chilense as an intermediary. After a series of backcrosses of the three-genome hybrid F1 (L. esculentum ×L. chilense) ×L. peruvianum var humifusum withL. esculentum, accompanied by selection for resistance to some economically important diseases, several lines were established. One of these lines, Cm 180, which showed resistance toClavibacter michiganensis subsp.michiganensis, was subjected to genetic analysis. This resistance was found to be controlled by a single dominant gene (Cm) that was not allelic to the gene originating fromL. hirsutum f.glabratum. ThisCm gene was genetically mapped on chromosome 4. The germ plasm ofL. peruvianum var humifusum in combination withL. chilense was transferred intoL. esculentum. Different breeding lines possessing resistance to various diseases and pests could be developed from this material. 相似文献
9.
Insect immune resistance to parasitoids 总被引:3,自引:0,他引:3
Insect host-parasitoid interactions involve complex physiological, biochemical and genetic interactions. Against endoparasitoids, immune-competent hosts initiate a blood cell-mediated response that quickly destroys the intruders and envelops them in a multilayered melanotic capsule. During the past decade, considerable progress has been made in identifying some of the critical components of the host response, mainly because of the use of efficient molecular tools. This review examines some of the components of the innate immune response of Drosophila, an insect that has served as an exceptionally good experimental model for studying non-self recognition processes and immune cell signaling mechanisms. Topics considered in this review include hematopoiesis, proliferation and adhesion of hemocytes, melanogenesis and associated cytotoxic molecules, and the genetic aspects of the host-parasitoid interaction. 相似文献
10.
Influence of carbon dioxide on growth and product kinetics of industrially important micro-organisms is essential for the interpretation of a bioprocess. In this research, the CO? effects on productivity and growth rate of micro-organisms have been studied by using a variety of kplug. The applied method is based on a different concentration of CO? in the headspace of ventilation flasks. The presented method is simple, inexpensive and shows similar results compared to large-scale fermentation regarding the evolution of CO? in a batch system. For the investigation of the proposed method, experiments employing Arxula adeninivorans LS3, Corynebacterium glutamicum (DM1730 and ATCC WT13032) and Hansenula polymorpha DSM70277 as model organisms in the ventilation flasks are performed. The fermentations in the RAMOS (respiratory activity monitoring system) device were carried out with a normal aeration rate (1 vvm) and under the same operating conditions as the ventilation flask f1. The modified unsteady-state model was used to predict the operation conditions of a biological system in the ventilation flasks. In the present study, a novel and easy method for the quantification of CO? sensitivity of micro-organisms in shaken bioreactors (called ventilation flask) was achieved. 相似文献
11.
Rafael Fernández-Muñoz María Salinas Eva Domínguez Marta Álvarez Jesús Cuartero 《Acta Physiologiae Plantarum》2000,22(3):358-359
The two-spotted spider mite (Tetranychus urticae Koch) is an important pest of tomato (Lycopersicon esculentum Mill.) crops in temperate regions as this spider mite has a very large capacity for population increase and causes severe
tomato yield losses. There is no described tomato cultivar fully resistant to this pest, although resistant accessions have
been reported within the green-fruited tomato wild species L. pennellii (Corr.) D’Arcy and L. hirsutum Humb. & Bonpl. We observed a L. pimpinellifolium (Jusl.) Mill. accession, ‘TO-937’, which seemed to be completely resistant to mite attacks and we crossed it with the susceptible
L. esculentum cultivar. ‘Moneymaker’ to obtain a family of generations consisting of the two parents, the F1, the F2, the BC1 to L. esculentum, and the BC1 to L. pimpinellifolium. This family was evaluated for mite resistance in a polyethylene greenhouse using an experimental design in 60 small complete
blocks distributed along 12 double rows. Each block consisted of five F2 plants in one row and one plant of each of the two parents, the F1, the BC1 to L. esculentum, and the BC1 to L. pimpinellifolium in the adjacent row. Plants at the 10–15 leaf stage were artificially infested by putting on them two pieces of French bean
leaf heavily infested with T. urticae. After two months, evaluations of infestation were made by visual observation of mite nets and leaf damage. Plants that were
free of signs of mite reproduction on the top half were considered as resistant, plants with silky nets only on their basal
leaves, intermediate, and plants with mite reproduction on both basal and top canopies were scored as susceptible. Dominance
for resistance appeared because all the ‘To-937’, BC1 to L. pimpinellifolium, and F1 plants were resistant. Not all ‘Moneymaker’ plants behaved as susceptible because 35% of plants were intermediate. In the
BC1 to L. pimpinellifolium and the F2, most plants were scored as resistant, only 7 % BC1 and 3 % F2 plants were intermediate, and a single F2 plant (0.3 %) was susceptible. With these figures, resistance seemed to be controlled by either four or two genes according
to whether segregation in the BC1 or in the F2, respectively, were considered. These results could in part be explained because of appearance of negative interplot interference
due to the high frequency of resistant genotypes within most of the generations. Therefore, the family was evaluated again
but using a different experimental design. In the new experiment, 16 ‘TO-937’, 17 ‘Moneymaker’, 17 F1, 37 BC1 to L. pimpinellifolium, 38 BC1 to L. esculentum, and 125 F2 plants were included. Each of these test plants was grown besides a susceptible ‘Moneymaker’ auxilliary plant that served
to keep mite population high and homogeneous in the greenhouse. Negative interplot interference was avoided with this design
and all the ‘TO-937’, F1, and BC1 to L. pimpinellifolium plants were resistant, all ‘Moneymaker’ test plants were susceptible, and 52 % BC1 to L. esculentum and 25 % F2 plants were susceptible, which fitted very well with the expected for resistance governed by a single dominant gene. The
simple inheritance mode found will favour sucessful introgression of mite resistance into commercial tomatoes from the very
close relative L. pimpinellifolium. 相似文献
12.
13.
Lin F Kong ZX Zhu HL Xue SL Wu JZ Tian DG Wei JB Zhang CQ Ma ZQ 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2004,109(7):1504-1511
Scab disease caused by Fusarium spp. has been a major concern for both wheat producers and consumers. Deployment of scab-resistant varieties is the major strategy to curb this disease. To identify the scab resistance genes in wheat cv. Wangshuibai, we produced a F6:7 recombinant inbred line (RIL) population by crossing Wangshuibai with the scab-susceptible cultivar Nanda2419. The RILs were evaluated for scab resistance in the field by single floret inoculation in two replicates in 2002 and one replicate in 2003. The number of diseased spikelets (NDS) and the length of diseased rachides (LDR) were investigated to reflect the Type II resistance. Among 654 simple sequence repeat (SSR) markers surveyed, 326 were found to be polymorphic between the parents. A partial molecular map was constructed with these markers that covered over 2,210 cM of the wheat genome. Six chromosome regions showed association with both NDS and LDR in a one-way anova analysis, even though the variation explained by them varied between the two traits. Eight intervals were detected for their association with Type II resistance through interval mapping, five of which were not identified in single-point analysis. The quantitative trait loci (QTL) with large effects were the ones in the interval of Xgwm533-3–Xgwm533-1 on chromosome 3B and in the interval of Xwmc539–Xbarc024 on chromosome 6B, whose alleles favoring resistance originate from Wangshuibai. In addition, a QTL whose resistance allele originated from Nanda2419 was consistently detected in the interval of Xs1021m–Xgwm47-1 on chromosome 2B. These results suggest that Wangshuibai is the major source for Type II resistance in this population. The markers associated with these QTL would facilitate the use of scab-resistant genes of Wangshuibai in scab resistance breeding programs of wheat.F. Lin and Z.X. Kong have equally contributed to this work. 相似文献
14.
Seong-Lyul Rhim Hwa-Jin Cho Byung-Dong Kim Wolfgang Schnetter Klaus Geider 《Molecular breeding : new strategies in plant improvement》1995,1(3):229-236
A crystal -endotoxin gene ofBacillus thuringiensis subsp.tenebrionis (B.t.t.) encoding a coleopteran insect-specific toxin was used to construct a chimeric gene which expressed the toxin in plant cells. Via anAgrobacterium tumefaciens binary vector system, the toxin gene was transferred into tomato cells. From leaf disks recombinant plants were regenerated. Hybridization experiments demonstrated that these plants synthesized toxin-specific mRNA of the expected size. Transgenic tomato plants with the chimericB.t.t. toxin gene contained a 74 kDa protein which cross-reacted with toxin antibodies. The expression caused a significant insecticidal activity of the transgenic tomato plants against Colorado potato beetle larvae. 相似文献
15.
16.
Is xylem cavitation resistance a relevant criterion for screening drought resistance among Prunus species? 总被引:1,自引:0,他引:1
Fruit trees are likely to suffer from the effects of severe drought in the future; however, sound criteria for evaluating the species' ability to survive these extreme conditions are largely missing. Here, we evaluated the feasibility of using xylem cavitation resistance as a tool for screening Prunus species for drought resistance. Ten different Prunus species were selected to cover a large range of water requirements, from hydrophilic to xerophilic types. Shoot cavitation resistance was evaluated with the new Cavitron technique. At this inter-specific level, cavitation resistance was related to species drought resistance, with xerophilic species being less vulnerable to cavitation. The Cavitron technique enabled species characterization that required a short time and small amounts of plant material. This technique could be used to evaluate the drought resistance of a limited number of fruit tree genotypes. Genotype screening on a larger scale, however, would likely require another approach. Out of a number of anatomical traits tested, a significant correlation was found between cavitation resistance and inter-vessel wall thickness across species. This anatomical trait is, therefore, suggested as a possible alternative to direct cavitation estimates and could be included as a screening criterion in breeding programs for drought resistance of Prunus genotypes. 相似文献
17.
18.
We present experimental data on susceptibility to columnaris disease, caused by the bacterium Flavobacterium columnare, in hybrid catfish (female channel catfish Ictalurus punctatus × male blue catfish I. furcatus) (C×B). Under our experimental conditions, C×B hybrids were significantly more resistant to columnaris disease caused by the highly virulent strain of F. columnare BGFS-27 (genomovar II) than channel catfish and blue catfish. Channel and blue catfish cumulative mortalities after immersion challenge were 74 and 87%, respectively, whereas mortality in the C×B hybrid was 31%. Susceptibility to the strain ARS-1 (genomovar I) was lower among all catfishes, although channel catfish was the least resistant species at 32% cumulative mortality. By contrast, C×B hybrid and blue catfishes were strongly resistant to the ARS-1 strain, with <10% mortality. Our data suggest enhanced disease resistance of the C×B hybrid to columnaris disease. 相似文献
19.
QTL analysis of late blight resistance in a diploid potato family of Solanum phureja × S. stenotomum
Costanzo S Simko I Christ BJ Haynes KG 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2005,111(3):609-617
Field resistance to Phytophthora infestans (Mont.) de Bary, the causal agent of late blight in potatoes, has been characterized in a potato segregating family of 230 full-sib progenies derived from a cross between two hybrid Solanum phureja × S. stenotomum clones. The distribution of area under the disease progress curve values, measured in different years and locations, was consistent with the inheritance of multigenic resistance. Relatively high levels of resistance and transgressive segregations were also observed within this family. A genetic linkage map of this population was constructed with the intent of mapping quantitative trait loci (QTLs) associated with this late blight field resistance. A total of 132 clones from this family were genotyped based on 162 restriction fragment length polymorphism (RFLP) markers. The genome coverage by the map (855.2 cM) is estimated to be at least 70% and includes 112 segregating RFLP markers and two phenotypic markers, with an average distance of 7.7 cM between two markers. Two methods were employed to determine trait–marker association, the non-parametric Kruskal–Wallis test and interval mapping analysis. Three major QTLs were detected on linkage group III, V, and XI, explaining 23, 17, and 10%, respectively, of the total phenotypic variation. The present study revealed the presence of potentially new genetic loci in this diploid potato family contributing to general resistance against late blight. The identification of these QTLs represents the first step toward their introgression into cultivated tetraploid potato cultivars through marker-assisted selection. 相似文献