Effect of Inoculant Rate on Nodulation and Various Agronomic Traits of Soybean

In a soil lacking indigenous Bradyrhizobium japonicum , soybean ( Glycine max [L.] Merr.) nodulation depends upon the number of rhizobia applied with the inoculum. This field study reports the effect of different rates of applied rhizobia on nodulation, dry matter and nitrogen content in soybean in a Mediterranean soil lacking B. japonicum.
Treatments included six rates of B. japonicum , ranging from 2.5 × 10⁴ to 6.075 × 10⁶ rhizobia cells per seed applied to the seed as peat inoculant at planting, 100 kg N ha⁻¹ and an uninoculated control. The experiment was conducted in an Entisol soil. Regression analysis showed linear relationship between the rate of applied rhizobia and the number of the nodules per plant or the dry weight per nodule. In early stages of development (32 and 68 days after planting) plant dry weight was not affected by inoculation rate. At harvest a rate of 7.5 × 10⁴ rhizobia cells per seed was necessary for maximum total and stover dry weight. A higher rate, 6.75 × 10⁵ rhizobia cells per seed, was required to obtain maximum grain yield, total N content in plant tops and grain N content. Grain percentage N was increased up to 2.025 × 10⁶ rhizobia cells per seed. Nitrogen application increased grain yield, total N content and grain N content at the same level as the lower inoculation rate.     

Low pH and aluminum tolerance of Bradyrhizobium strains isolated from acid soils in Indonesia

Sixty-seven strains of Bradyrhizobium isolated from soybean plants growing on acid soils in West Java and Sumatra, Indonesia, were examined for the effect of the pH and aluminum concentration on their growth in nutrient media, compared with 61 strains of Bradyrhizobium from soils in Japan. The results in this study indicated that the indigenous population of Bradyrhizobium in the soils of Indonesia showed a large difference in acid- and Al-tolerance from that of Japan. Eighty-five and 48% of the isolates from Japanese soils and Indonesian soils, respectively, were unable to grow in YEM broth at pH below 4.5. The acid-tolerance was correlated with AI-tolerance of the isolates on YEM agar plates at pH 4.4. Seventy-five percent of the isolates that grew in YEM broth at pH 4.5 were also resistant to 400 µM Al on the YEM plates. Acetylene reduction assay of the root nodules revealed that 3 of the acid- and Al-tolerant isolates from Indonesian soils showed a significantly high nitrogen fixation activity.     

Genetic diversity of fast-and slow-growing soybean rhizobia determined by random amplified polymorphic DNA analysis

The genetic relationships among six strains of rhizobia, including three strains of Rhizobium fredii and three strains of Bradyrhizobium japonicum, was determined using random amplified polymorphic DNA (RAPD) technique. In this study, 46 arbitrary 10mer primers were employed for RAPD, generating a total of 251 informative fragments. A dendrogram of phylogenetic relationships among the six strains was constructed. The results indicated that geographical distribution may affect phylogeny, as there were closer relationships among the four Taiwanese strains, SB138, SB562, SB368 and SB651, than between these strains and USDA192, which originated from mainland China. The strain USDA110, obtained from the United States, was used in the parsimony analysis. The greatest similarity (55.6%), existed between two strains of B. japonicum, SB562 and SB138, which both, and the lowest R. fredii (44.4%) between two strains of R. fredii, SB368 and USDA192. We also found a RAPD marker specific to the four Taiwanese SB strains used in the study. The RAPD technique is a potential tool for the identification of the genetics and systematics of different populations. Received: 23 January 1997     

Relative efficiency,ureide transport and harvest index in soybeans inoculated with isogenic HUP mutants of Bradyrhizobium japonicum

Summary Differences between isogenic uptake hydrogenase (HUP) mutants of Bradyrhizobium japonicum in terms of nodule efficiency, N₂ fixation and N incorporation into various plant parts were studied in a monoxenic greenhouse experiment in order to confirm previous results with soybeans and beans inoculated with various HUP⁺ and HUP^– strains. The HUP+ revertant PJ17-1 of a HUP^– mutant (PJ17) of strain USDA DES 122 showed a completely restored relative efficiency (100% versus 78±2% for the HUP^– mutant), higher nodule efficiency (N₂ fixed per g nodules), higher ureide-N transport rates, higher N contents in pods and higher N harvest indices. All these observations confirm previous experiments with HUP⁺ and HUP^– strains.     

Application of Bradyrhizobium japonicum and Phosphorus Fertilization Improved Growth,Yield and Nodulation of Soybean in the Sub-humid Hilly Region of Azad Jammu and Kashmir,Pakistan

Two separate experiments (pot and field) were conducted to examine the response of soybean to Bradyrhizobium japonicum and phosphorus (P) fertilization. Different treatments were i) Rhizobium strains (0, S377, S379, and the mixture of S377 + S379 i.e. S₀, S₁, S₂, S₃); ii) phosphorus (field only, 0, 50, 100 kg ha-¹i.e. T₀, T₁, T₂) and iii) two soils (pot only) i.e. autoclaved (A₁) and non-autoclaved (A₀). A soybean cultivar NARC-1 was tested for estimating growth traits, nodule number and mass, root development and yield traits. In the pot experiment, total number of nodules both in the A₀ and A₁ were negligible but increased significantly following the application of Bradyrhizobium japonicum. In the field experiment, number of nodules increased from 6 in the control treatment without strains to a maximum of 86 in S₃T₁. Shoot dry weight increased significantly from 11.8 g plant-¹ in the control soil to 15.6 g plant-¹ in S₃T₁. Root length was increased but root mass was unaffected. Soybean seed yields ranged between 615 and 1003 kg ha-¹ against 543 kg ha-¹ in the control soil indicating a maximum of 85% increase over control. Shoot dry weight and seed yield had significant correlation with nodulation (R² = 0.91). The results of experiments revealed significant positive effects of rhizobium inoculation and P fertilization on growth, nodulation and yield of soybean and, generally, mixture of strains (S₃) was more effective than the strains S₁ and S₂. Results also indicated that high application of P (100 kg P₂O₅ ha-¹) reduced the efficiency of inoculants for nodule mass and seed yield.     

大豆慢生根瘤菌（Bradyrhizobium ddjaponicum）的血清型研究

以自东北地区分离的8株大豆慢生根瘤菌为供试菌用交叉凝集反应比较了它们与目前国内外已报道 的15株大豆慢生根瘤菌标准血清型菌株之间的血清学关系。研究结果表明：（1）菌株93H10F5和HJ15不与供试标准血清型菌株发生交叉凝集瓜在,分别命名为O14和O15血清型,（2）菌株HJ19、HJ28、93F42与标准血甭型菌株USDA94有交叉凝集反应,进一步的抗原吸收试验结果表明：HJ19和HJ28的抗原组成完全相同,命名为O3bxl血清亚型;USDA94仅与HJ19有交叉反应,命名为O３ab血清亚型,９３Ｆ４２也与ＨＪ１９有部分共同抗原,命名为Ｏ３de血清亚型。（３）菌株９３ＨＡ８与标准血清型菌株USDA135有部分共同抗原,分别命名为O12bc和O12ab血清亚型,（4）标准菌株USDA127、USDA129与USDA123有交叉凝集反应,抗原吸收试验分别将其细分为O12bc和O12ab血甭亚型。（4）标准菌株USDA127、USDA129与USDA123有交叉凝集反应,抗原吸收试验分别将其细分为O10ab。O10de和O10xxl等3个血清亚型。（5）将USDA的10个标准菌株重新命名为O1,O2,O4,O5,O6,O7,O8,O9,O11和O13血清型。     

抗药性根瘤菌基因工程菌的构建与应用

用三亲本杂交的方法将外源抗药性质粒导入到高效固氮的根瘤菌 Tal377中,外源质粒在 Tal377中能正常表达,但不影响其原有的固氮结瘤能力。利用此抗药性根瘤菌所携带的抗药性,在接种此根瘤菌的同时结合施加一定浓度的抗菌素,抗药性根瘤菌与出发菌株相比表现出一定程度地提高其结瘤固氮能力和占瘤率。     

Soil aggregate as a favorable habitat for Bradyrhizobium japonicum strains

Abstract

Rhizobial cells are present in soils as saprophytes after the decay of host plant nodules, and must survive in the soil until the next encounter with the infection sites of the host plant root. Biotic and abiotic environmental factors affect the population size of these rhizobia in the soil (Vincent 1977). Precise estimation of the population size of the native and the introduced rhizobia in the soil is necessary to study the conditions for the successful nodule formation by introduced strains.