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51.
Characterization of quantitative trait loci (QTLs) in cultivated rice contributing to field resistance to sheath blight (Rhizoctonia solani) 总被引:1,自引:0,他引:1
Zhikang Li S. R. M. Pinson M. A. Marchetti J. W. Stansel W. D. Park 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(2):382-388
Sheath blight, caused by Rhizoctonia solani, is one of the most important diseases of rice. Despite extensive searches of the rice germ plasm, the major gene(s) which give complete resistance to the fungus have not been identified. However, there is much variation in quantitatively inherited resistance to R. solani, and this type of resistance can offer adequate protection against the pathogen under field conditions. Using 255 F4 bulked populations from a cross between the susceptible variety Lemont and the resistant variety Teqing, 2 years of field disease evaluation and 113 well-distributed RFLP markers, we identified six quantitative trait loci (QTLs) contributing to resistance to R. solani. These QTLs are located on 6 of the 12 rice chromosomes and collectively explain approximately 60% of the genotypic variation or 47% of the phenotypic variation in the LemontxTeqing cross. One of these resistance QTLs (QSbr4a), which accounted for 6% of the genotypic variation in resistance to R. solani, appeared to be independent of associated morphological traits. The remaining five putative resistance loci (QSbr2a, QSbr3a, QSbr8a, QSbr9a and QSbr12a) all mapped to chromosomal regions also associated with increased plant height, three of which were also associated with QTLs causing later heading. This was consistent with the observation that heading date and plant height accounted for 47% of the genotypic variation in resistance to R. solani in this population. There were also weak associations between resistance to R. solani and leaf width, which were likely due to linkage with a QTL for this trait rather than to a physiological relationship. 相似文献
52.
The cost of herbicide resistance in white-chicory: ecological implications for its commercial release 总被引:2,自引:0,他引:2
C. Lavigne H. Manac'h C. Guyard J. Gasquez 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,91(8):1301-1308
Applications for the commercial release of herbicide-resistant crops, most of them transgenic, are likely to become more frequent in the coming years. The ecological concerns raised by their large scale use call for risk-assessment studies. One of the major issues in such studies is the relative fitness of the resistant line compared to the susceptible when no herbicide is applied since this will largely determine the long-term fate of the resistance gene outside of the field. Here we report on a comparison of a sulfonylurea-resistant line of white-chicory regenerated from a non-mutagenized cell culture with a supposedly isogenic susceptible biotype. The plants were grown in experimental plots at a range of densities in a replacement series. The reproductive output of the plants decreased with increasing density but no significant difference was found between the two lines for any vegetative or reproductive trait at any density. This suggests that no cost is associated with the mutation causing the resistance and that the resistance gene would not be selected against if it escaped to populations of wild chicories. 相似文献
53.
Júlia Tandori László Nagy Ágnes Puskás Magdolna Droppa Gábor Horváth Péter Maróti 《Photosynthesis research》1995,45(2):135-146
A spontaneous mutant (R/89) of photosynthetic purple bacterium Rhodobacter sphaeroides R-26 was selected for resistance to 200 M atrazin. It showed increased resistance to interquinone electron transfer inhibitors of o-phenanthroline (resistance factor, RF=20) in UQo reconstituted isolated reaction centers and terbutryne in reaction centers (RF=55) and in chromatophores (RF=85). The amino acid sequence of the QB binding protein of the photosynthetic reaction center (the L subunit) was determined by sequencing the corresponding pufL gene and a single mutation was found (IleL229 Met). The changed amino acid of the mutant strain is in van der Waals contact with the secondary quinone QB. The binding and redox properties of QB in the mutant were characterized by kinetic (charge recombination) and multiple turnover (cytochrome oxidation and semiquinone oscillation) assays of the reaction center. The free energy for stabilization of QAQB
– with respect to QA
–QB was GAB=–60 meV and 0 meV in reaction centers and GAB=–85 meV and –46 meV in chromatophores of R-26 and R/89 strains at pH 8, respectively. The dissociation constants of the quinone UQo and semiquinone UQo
– in reaction centers from R-26 and R/89 showed significant and different pH dependence. The observed changes in binding and redox properties of quinones are interpreted in terms of differential effects (electrostatics and mesomerism) of mutation on the oxidized and reduced states of QB.Abbreviations BChl
bacteriochlorophyll
- Ile
isoleucine
- Met
methionin
- P
primary donor
- QA
primary quinone acceptor
- QB
secondary quinone acceptor
- RC
reaction center protein
- UQo
2,3-dimethoxy-5-methyl benzoquinone
- UQ10
ubiquinone 50
This work is dedicated to the memory of Randall Ross Stein (1954–1994) and is, in a small way, a testament to the impact which Randy's ideas have had on the development of the field of competitive herbicide binding. 相似文献
54.
Crosses were made between the Asian cockroach,Blattella asahinai Mizukubo, and resistant strains of the German cockroach,B. germanica (L.), to assess the transfer of pyrethroid resistance to the progeny and to study the inheritance mechanism(s) involved.
It was shown that the strain of Asian cockroaches studied was susceptible to four pyrethroids. F1 progeny were essentially susceptible to the same compounds. Tests with F2 progeny and those from backcrosses to the resistant parent indicated that the data for each pyrethroid fit an hypothesis
of simple, autosomal, nearly completely recessive inheritance. The results are discussed from the standpoint of the impact
of the Asian genome on the inheritance mechanism(s). 相似文献
55.
Pyrethroid resistant and susceptible adults ofHelicoverpa armigera (Lepidoptera: Noctuidae) were screened for tolerance to pyrethroids after 6 wk or 12 wk pupal diapuse. Resistant larvae and
F2 larvae from a cross between resistant and susceptible parents (two replicates), were reared under conditions to induce pupal
diapause. After eclosion, adults were tested in glass vials coated with the pyrethroid fenvalerate, at a dose (DD) that is
known to discriminate between susceptible and heterozygous resistant individuals. In all diapause experiments, the frequency
of resistance was lower in the test groups that had experienced diapause compared with the non-diapausing control group. The
underlying cause of the decline is not certain but selective mortality of resistant versus susceptible individuals could not
account for all the difference in two of the three experiments — tolerance to the pyrethroid, fenvalerate, is most likely
to have declined either as a consequence of diapause or from the extended time of development associated with diapause. These
results indicate that monitoring programs could underestimate pyrethroid resistance frequencies when usingH. armigera adults emerging from diapause. 相似文献
56.
Interferon antibodies in patients with infectious diseases 总被引:2,自引:0,他引:2
G. Antonelli E. Simeoni M. Currenti F. De Pisa V. Colizzi M. Pistello F. Dianzani 《Biotherapy》1997,10(1):7-14
Interferons (IFNs) are generally recognized as the most important therapeutic agent in some infectious diseases such as chronic
hepatitis B and C. Since the early clinical trials it was documented that the therapeutic use of IFNs could be complicated
by the development of antibodies able to neutralize or to bind to the IFN molecule.
After several years of research it is now widely accepted that the presence of circulating anti-IFN antibodies may affect
the response to IFN.
Here we summarize what is currently know on the clinical significance of antibodies to IFN in IFN-treated viral diseases patients. 相似文献
57.
58.
A transformation method based on a dominant selectable marker (benomyl resistance) was developed for the rice blast fungus Magnaporthe grisea. The heterologous gene for -tubulin from Neurospora crassa (pBT3) was used to obtain benomyl-resistant M. grisea transformants at a frequency of 20 to 30/g of DNA. Control transformations carried out with a plasmid conferring hygromycin resistance or a derivative of pBT3 containing a repetitive DNA sequence, yielded the same frequency of transformation as that of pBT3. Molecular analysis of the transformants indicated multiple integration of the vector DNA. 相似文献
59.
A review on salinity adaptation of marine molluscsbased on mainly Russian scientific literature ispresented. The existence of two relativelyindependent systems of adaptation to extreme(resistance level) and moderate (tolerance level)changes of environmental salinity was shown. Theresistance of molluscs is based mainly on an impededwater-salt exchange with the external medium due tomantle cavity hermetization. The tolerance ofmolluscs is determined by cellular mechanisms ofadaptation. Reversible changes of protein and RNAsynthesis, alteration of the pattern of multiplemolecular forms of different enzymes, and theregulation of ionic content and cell volume wereshown to be of importance for the above mentionedmechanisms. The efficiency of resistance andtolerance adaptations to salinity changes may varyin different species and in different colourphenotypes of the same species (intrapopulationalpolymorphism). Parasites (trematodes) may suppressthe resistance of the mollusc-host to extremesalinity changes without effecting the host'scapacity for adaptive changes in salinitytolerance. 相似文献
60.
Detailed studies on the production of individual leaves, and the development of powdery mildew on them, were made in field plots of winter barley sown on different dates. The greater severity of the disease on early-sown than on later-sown seedlings during the autumn and winter can probably be explained mainly by changes in the abundance of inoculum and the suitability of the weather for infection. Results from glasshouse experiments suggest that the differences may be reinforced by direct effects of vernalisation on the susceptibility of seedlings to the disease. Contrary effects of sowing date on mildew severity during summer are probably due to the progressively greater resistance to mildew of the later-formed than of seedling leaves, and the earlier appearance of corresponding leaves on early-sown than on later-sown plants. Early sowing can also increase the total number of leaves produced per stem. Therefore, because resistance of the leaves increases progressively, the maximum degree of resistance expressed by the later-formed (e.g. flag) leaves will often be greater on early-sown than on later-sown plants. 相似文献