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51.
52.
胡枝子属根瘤菌的多相分类研究 总被引:5,自引:0,他引:5
采用了数值分类、全细胞可溶性蛋白电泳分析、DNAG+Cmol%和DNA相关性的测定以及16SrDNAPCRRFLP分析等多相分类技术对来源于不同地区的16种寄主的胡枝子根瘤菌进行了系统的分类研究。数值分类的结果表明,在67%的相似性水平上,全部供试菌可以分为快生型根瘤菌和慢性型根瘤菌两大群,在80%的相似性水平上又可分为四个亚群。在此基础上,对各亚群的胡枝子根瘤菌进行了DNA相关性的测定,以进一步证实和确定它们的分类地位,并通过16SrDNAPCRRFLP分析对各亚群的系统发育关系进行了初步研究。 相似文献
53.
Eighty soybean cultivars were assessed for their potential for nodulation and nitrogen fixation with indigenous rhizobia in a Nigerian soil. Seventy-six days after planting (DAP) 87%, 3% and 10% of the soybean cultivars had from 0 to 30, 31 to 60 and over 61 nodules/plant, respectively. Only 8% had a nodule dry weight of 600 to 1100 mg/plant. At 84 DAP the proportion of nitrogen derived from the atmosphere (Ndfa) ranged from 0 to 65% 16% of the cultivars derived 51 to 65% of their N2 from the atmosphere. The diversity of soybean germplasm and the variation in nodulation and N2 fixation permitted the selection of the five best cultivars in terms of their compatibility with indigenous rhizobia, % Ndfa and the amount of N2 which they fixed. 相似文献
54.
Biological nitrogen fixation (BNF) technology with special reference to Rhizobium-legume symbiosis is growing very rapidly with the hope of combatting world hunger by producing cheaper protein for animal and human consumption in the Third World. One can see rapid progress made in the biochemistry and molecular biology of symbiotic nitrogen fixation in general; however, less progress has been made on the ecological aspects despite the fact that an enormous amount of literature is available on inoculation problems and on agronomic aspects of symbiotic nitrogen fixation. So far most information on Rhizobium concerns fast-growing rhizobia and their host legume. Although it is essential that food production using BNF technology should be maximized in the Third World, the least work has been done on slow-growing rhizobia, which are generally found in tropical and sub-tropical soils. The majority of the developing countries are in tropical and sub-tropical regions. Except for R. japonicum, a microsymbiont partner of soybean (Glycine max), the majority of the slow-growing rhizobia belong to the cowpea group, and we refer to cowpea rhizobia as tropical rhizobia species. In this review we have tried to consolidate the recent progress made on ecology and genetics of tropical rhizobia. By using recombinant DNA technology techniques it is expected that super strains of rhizobia with desirable characteristics can be produced. One must evaluate the efficiency and effectiveness of these genetically manipulated laboratory strains under field conditions. In conclusion, if one aims at combatting hunger in the Third World using BNF technology, an intensive research programme on fundamental and applied aspects of tropical rhizobia species is suggested. This involves close cooperation between molecular biologists and microbial ecologists. 相似文献
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Five exopolysaccharide-deficient mutants were isolated after rhizobial strain 107 was subjected to transposon Tn5 mutagenesis. The amount of EPS produced by the mutants was dramatically decreased to between 3% and 6% of wild-type level. All mutants carried a singel copy of Tn5. Two mutants (NA3 and NA10) were complemented by the R. meliloti exoA gene and the functionally equivalent exoD gene of Rhizobium sp. strain NGR234. Two other mutants (NA7 and NA8) were complemented by the R. meliloti exoB gene and the functionally equivalent NGR234 exoC gene. The remaining mutant (NA11) was not complemented by any exo genes of R. meliloti or Rhizobium NGR234. All mutants induced normal nitrogen-fixing nodules on Astragalus sinicus, an indeterminate nodulating host. 相似文献
58.
Laboratory, growth chamber and field experiments were conducted to select among 226 isolates of Rhizobium meliloti for the ability to grow, nodulate alfalfa (Medicago sativa L.) and support N2-dependent plant growth between 9° and 12°C. There was wide variation in the abilities of R. meliloti isolates to grow and form nodules at 10°C. Culture doubling times (td) varied from 1 to 155h, and the number of nodules formed on alfalfa in growth pouches in 2 weeks varied from 0 to 3.8 nodules
per plant. Nodulation occurred at 9°C, but there was no significant N2-dependent plant growth at this temperature. However, several isolates of R. meliloti had the ability to nodulate alfalfa and produce N2-dependent growth at root temperatures between 10° and 12°C root temperature than did 14 other isolates tested. In field experiments,
inoculation with strain NRG-34 resulted in greater nodule numbers, nodule weight, proportion of nodules occupied by the inoculant
strain and plant weight than did inoculation with a commercial strain (NRG-185). These results permitted selection of a strain
with better low-temperature competitive abilities than the currently available commercial strains. 相似文献
59.
The peribacteroid membrane 总被引:4,自引:0,他引:4
The objective of this review is to summarise current knowledge about the structure and function of the peribacteroid membrane from the root nodules of leguminous plants. The information is presented in terms of development of this symbiotic membrane from its origin, through proliferation and in the mature state. There are clear indications that the peribacteroid membrane has a distinct structure and function at each developmental stage. The mature peribacteroid membrane has been the most intensively studied. The lipid and protein content of the mature peribacteroid membrane is discussed with particular emphasis on genetic and functional studies of the proteins. The mechanism and control of peribacteroid membrane biogenesis is also discussed. There is evidence for a specific biogenetic pathway for this membrane which requires both symbiotic partners for its correct functioning. 相似文献
60.
Facultative nitrogen fixation by legumes in the central Congo basin is downregulated during late successional stages 下载免费PDF全文
The contribution of the legume community to the nitrogen cycle during natural forest regeneration remains poorly understood. We systematically assessed the changes in abundance and nodulation status of all legumes, across taxa and plant types, in a forest succession gradient in the Equateur Province of the Democratic Republic of the Congo. Our results clearly show that symbiotic N2 fixation is downregulated during late successional stages. 相似文献