Population size, distribution, and symbiotic characteristics of indigenous Bradyrhizobium spp. that nodulate TGx soybean genotypes in Africa
Population size, distribution, and symbiotic characteristics of indigenous Bradyrhizobium spp. that nodulate TGx soybean genotypes in Africa
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DOI：
10.1016/j.apsoil.2006.05.006
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发表时间：
2007-01-01
影响因子：
4.8
通讯作者：
Sanginga, N.
中科院分区：
文献类型：
--
作者：
Abaidoo, R. C.;Keyser, H. H.;Sanginga, N.
非洲许多潜在大豆田土壤的特点是生物固氮（BNF）活性水平低，如果不添加无机氮肥或外施大豆根瘤菌，往往无法支持大豆高产。采用最可能数（MPN）技术测定了TGx大豆基因型（非混杂的北美大豆基因型与混杂的亚洲大豆基因型的杂交）、豇豆或北美大豆cv的缓生根瘤菌群体。克拉克四号，在9个非洲国家65个地点的土壤中进行了研究。从这些土壤中分离出的菌株与日本慢生根瘤菌USDA110的共生效果进行了比较。缓生根瘤菌种群大小为0 ~ 10(4)cells g(-1) soil。在72%的土壤样品中检测到缓生根瘤菌（TGx）群体，在37%的土壤样品中检测到日本芽孢杆菌（Clark）群体。缓生根瘤菌（TGx）群体普遍偏低，在57%的样品中显著低于豇豆缓生根瘤菌群体。小于10个细胞g（-1）土壤的群体大小是常见的，因为这些在至少43%的土壤样品中被检测到。研究点日本白僵菌（Clark）的种群密度高于农田。缓生根瘤菌（TGx）种群与生物因子高度相关，但与非生物因子无关。低缓生根瘤菌（TGx）群体的频繁发生不太可能支持足够的最佳BNF以实现大豆高产，而日本芽孢杆菌（Clark）在研究领域的存在有可能损害预期来自本地缓生根瘤菌（Vigna）群体的选择压力。根据其对TGx大豆基因型和北美栽培品种Clark IV的有效性，可将慢生根瘤菌分离物分为4个共生表型组。共生表型组11分离物对两种大豆基因型的效果与日本芽孢杆菌菌株USDA110一样，而组IV分离物对TGx大豆基因型有效，但对Clark IV无效有足够的人口密度。(c) 2006 Elsevier B.V.版权所有
Soils of many potential soybean fields in Africa are characterized by low levels of biological nitrogen fixation (BNF) activities and often cannot support high soybean yields without addition of inorganic N fertilizers or external application of soybean rhizobia. The most probable number (MPN) technique was used to determine the bradyrhizobial populations that nodulate TGx soybean genotypes (a cross between nonpromiscuous North American soybean genotypes and promiscuous Asian soybean genotypes), cowpea or North American soybean cv. Clark IV, in soils from 65 sites in 9 African countries. The symbiotic effectiveness of isolates from these soils was compared to that of Bradyrhizobium japonicum strain USDA110. The bradyrhizobial population sizes ranged from 0 to 10(4) cells g(-1) soil. Bradyrhizobium sp. (TGx) populations were detected in 72% and B. japonicum (Clark) in 37% of the soil samples. Bradyrhizobium sp. (TGx) populations were generally low, and significantly less than that of the cowpea bradyrhizobial populations in 57% of the samples. Population sizes of less than 10 cells g(-1) soil were common as these were detected in at least 43% of the soil samples. B. japonicum (Clark) occurred in higher population densities in research sites compared to farmers' fields. Bradyrhizobium sp. (TGx) populations were highly correlated with biotic but not abiotic factors. The frequent incidence of low Bradyrhizobium sp. (TGx) populations is unlikely to support optimum BNF enough for high soybean yields while the presence of B. japonicum (Clark) in research fields has the potential to compromise the selection pressure anticipated from the indigenous Bradyrhizobium spp. (Vigna) populations. Bradyrhizobium isolates could be placed in four symbiotic phenotype groups based on their effectiveness on a TGx soybean genotype and the North American cultivar Clark IV. Symbiotic phenotype group 11 isolates were as effective as B. japonicum strain USDA110 on both soybean genotypes while isolates of group IV were effective on the TGx soybean genotype but not on the Clark IV. The group IV isolates represent a unique subgroup of indigenous bradyrhizobia that can sustain high soybean yields when available in sufficient population densities. (c) 2006 Elsevier B.V. All rights reserved.