Inoculation with the native Rhizobium gallicum 8a3 improves osmotic stress tolerance in common bean drought-sensitive cultivar

Abstract

Symbiotic nitrogen fixation potential in common bean is considered to be low in comparison with other grain legumes. However, it may be possible to improve the nitrogen fixation potential of common bean using efficient rhizobia. In order to improve osmotic stress tolerance of a drought-sensitive common bean cultivar (COCOT) consumed in Tunisia, plants were inoculated either by the reference strain Rhizobium tropici CIAT 899 or by inoculation with rhizobia isolated from native soils Rhizobium gallicum 8a3. Fifteen days after sowing, osmotic stress was applied by means of 25 mM mannitol (low stress level) or by 75 mM mannitol (high stress level). Fifteen days after treatment plants were harvested and different physiological and biochemical parameters were analysed. Results showed no significant differences between the studied symbioses under control conditions. However after exposure to osmotic stress our results showed better tolerance of COCOT to osmotic stress when inoculated with the native R. gallicum 8a3. This can be partially explained by better water-use efficiency in both leaves and nodules, better relative water content in nodules and better efficiency in utilization of rhizobial symbiosis as compared with COCOT-CIAT 899 symbiosis. Hence, the present study suggested the better use of native soil isolated strains for the inoculation of common bean in order to improve its performance and nitrogen fixation potential under stressful conditions.     

A supernodulating mutant isolated from soybean cultivar enrei

Abstract

Symbiotic nitrogen fixation in nodules of legumes depends on the complex interaction between the legume plant and (Brady)Rhizobium bacteria. Nodule formation and nitrogen fixation are closely regulated by both the host plant and the microsymbiont. Plant mutants with altered symbiotic performance are considered to be useful to gain a better understanding of the plant—microbe interactions in the legume—(Brady)Rhizobium symbiosis (Jacobsen 1984; Carroll et al 1985a, b; Park and Buttery 1988; Duc and Messager 1989; Gremaud and Harper 1989). Recently, Carroll et al. (1985a, b) have isolated the supernodulating mutants of the soybean cv. “Bragg,” which display a very large number of nodules and “nitrate-tolerant-symbiotic” (nts) characteristics. More recently, Gremaud and Harper (1989) have also isolated similar mutants from the soybean cv. “Williams.” These mutants not only provide materials that are useful for investigatings on the interaction in the nodule formation processes but also for agricultural practice. In particular, the nitrate-tolerance of these supernodulating mutants (Carroll et al. 1985b; Gremaud and Harper 1989) is useful for their cultivation in Japan where the level of soil nitrogen in fields is generally high. However, the cultivars previously used for the isolation of these mutants cannot adapt easily in Japanese climate due to different Maturity Group. Therefore, we attempted to isolate mutants with altered symbiotic phenotypes from the soybean cultivar “Enrei,” one of the most common cultivars in Japan.     

Hydrogenase Activity of Soybean Nodules Doubly Infected with Bradyrhizobium japonicum and B. elkanii

Rhizobitoxine (2-amino-4-(2-amino-3-hydropropoxy)-trans-but-3-erioic acid) is a phytotoxin produced by some strains of Bradyrhizobium species. Rhizobitoxine-producing strains often induce chlorosis in new leaves of soybean as a result of the synthesis of the toxin in nodules (Owens and Wright 1964; Owens et al. 1972). Some of the B. japonicum bacteroids possessing the hydrogen uptake (Hup) system are capable of ATP production by recycling H₂ evolved from nitrogenase (Evans et al. 1987). Adequate uptake hydrogenase activity in soybean bacteroids often enhances plant growth, as well as the efficiency of energy utilization during nitrogen fixation (Evans et al. 1987).     

Internal Mechanisms of Plant Adaptation to Aluminum Toxicity and Phosphorus Starvation in Three Tropical Forages

Many tropical forage grasses and legumes grow well in acid soils, adapting to excess aluminum (Al) and phosphorus (P) starvation stresses by using mechanisms that are still unclear. To determine these mechanisms, responses to Al toxicity and P starvation in three tropical forages were studied: two grasses, Brachiaria hybrid cv. ‘Mulato’ (B. ruziziensis clone 44-06 × B. brizantha cv. ‘Marandú’) and Andropogon gayanus, and one legume, Arachis pintoi. The tropical grasses tolerated high levels of Al toxicity and P starvation, with the Brachiaria hybrid maintaining very low levels of Al concentration in shoots. ²⁷Al Nuclear Magnetic Resonance spectroscopy (NMR) analysis revealed that, in the Brachiaria hybrid, Al makes complexes with some ligands such as organic-acid anions in the root symplast. The forages probably adapted to P starvation through high P-use efficiency. These experiments provide the first direct evidence we know of that organic acid anions within root tissue help detoxify Al in non-accumulator species such as the Brachiaria hybrid.     

Effects of difference in fertilization treatments on nitrification activity in tea soils

Abstract

It is generally recognized that the nitrification activity in acid soils is very low. Indeed, nitrification in mineral soils has been found to be negligible at pH values below 5.0 (Dancer et al. 1973; Nyborg and Hoyt 1978). However, it was reported that autotrophic nitrification occurred in some tea soils at pH levels far below 5.0 (Walker and Wickramasinghe 1979; Hayatsu and Kosuge 1993). An acidophilic ammonia-oxidizing bacterium has been recently isolated from strongly acidic tea soils in Japan (Hayatsu 1993). On the other hand, fertilization has-been considered to be an important factor influencing nitrification in agricultural soils. For example, several studies have shown that the addition of ammoniacal fertilizer to soils can lead to the increase of the populations of Nitrosomonas (McLaren 1971; Ardakani et al. 1974). Liming of acidic soils also tends to stimulate the nitrification activity (Dancer et al. 1973; Nyborg and Hoyt 1978). Although nitrification has been studied in a wide variety of agricultural soils, there is little information available on nitrification in tea soils. The effect of fertilization on nitrification in tea soils is poorly documented.     

Effect of P application on CEC,amounts of extractable nutrients,and corn yield in a Hydric Melanudand in the Philippines

In soils, next to nitrogen, phosphorus (P) is the second major growth-limiting factor for plants (Fox 1979). It is probably the most deficient soil-derived plant nutrient in Oxisols, Ultisols, acid Alfisols, and Andisols and the proper development of crops is frequently impossible without the application of P. P deficiency is a major nutritional problem in variable charge soils, especially the Andisols, where applied P is usually converted into an unavailable form. The P added to Andisols in fertilizers is readily sorbed to form noncrystal-line aluminum phosphate materials (Nanzyo 1987). Most uncultivated Andisols also show a very low P fertility and very low recovery of applied P fertilizers by crops (Shoji et al. 1993). In fact, P fixation is one of the growth-limiting factors for crops cultivated in Brazil (Fageria and Filho 1987).     

Biomass and Phosphorus Uptake Responses of Maize to Phosphorus Application in Three Acid Soils from Southern Cameroon

Abstract

A phosphorus (P) greenhouse experiment was carried out with maize (Zea Mays L.) using surface horizons of three contrasted acid soils from southern Cameroon. The objectives were (i) to assess causal factors of maize differential growth and P uptake and (ii) to explore plant–soil interactions in acid soils under increasing P supply. Shoot and root dry‐matter yield and P uptake were significantly influenced by soil type and P rate (P<0.000), but the interaction was not significant. Soil properties that significantly (P<0.05) influenced maize growth variables were available P, soil pH, exchangeable bases [calcium (Ca), magnesium (Mg)], and exchangeable aluminium (Al). Data ordination through principal‐component analysis highlighted a four‐component model that accounted for 88.1% of total system variance (TSV) and summarized plant reaction in acid soil condition. The first component, associated with 36.1% of TSV, pointed at increasing root–shoot ratio with increasing soil acidity and exchangeable Al. The second component (24.6% of TSV) highlighted soil labile P pool increase as a function of P rate. The third and fourth components reflected nitrogen (N) accumulation in soils and soil texture variability, respectively.     

Agronomic effectiveness of phosphate rock and superphosphate for aluminum‐tolerant and non‐tolerant sorghum cultivars

Abstract

About 35% of soils in Venezuela are acid and low in available phosphorus (P). To solve this problem farmers lime and apply phosphate fertilizers to the soils, but both lime and fertilizers are expensive. A good alternative to overcome soil acidity is the use of aluminum (Al)‐tolerant cultivars. The objective of this study was to test the hypothesis, by use of a pot experiment, that sorghum cultivars tolerant to Al toxicity are able to use P from phosphate rock more efficiently than are susceptible cultivars. Three sorghum (Sorghum bicolor L. Moench) cultivars, Chaguaramas III (Ch), AI‐tolerant, Decalb D59 (D59), and Pioneer 8225 (Pi), both Al‐susceptible, were grown in the greenhouse for 20 and 35 days in two acid soils fertilized with 0 and 100 mg P kg^‐1 as triple superphosphate (SP) and Riecito phosphate rock (PR). Santa Maria soil was very low in available P (2 mg kg^‐1) and highly saturated in Al saturation (64.5%) and Pao soil was higher in available P (20 mg kg^‐1) and low in Al saturation (6.5%). Chaguaramas dry matter production, P uptake and root length was higher in Santa Maria soil as compared with Pi and D59 when grown with both SP and PR fertilization. Chaguaramas response to PR in Pao soil was not as good as in Santa Maria soil. The results of our experiment suggest that Al‐tolerant Ch is able to utilize P from PR more efficiently in soils like Santa Maria than Al‐susceptible cultivare Pi and D59.     

Sulfur deficiency of rice plants in the Lower Volta area,Ghana

Abstract

It is well known that stem nodules are formed on the aerial parts of Aeschynomene spp. and Sesbania rostrata grown in the field (Yatazawa and Yoshida 1979; Dreyfus and Dommergues 1981; Yoshida et al. 1985). We have reported that stem nodules were successfully formed by inoculation of Rhizobium isolates derived from both stem and root nodules of A. indica (Yoshida et al. 1985; Sasakawa et al. 1986). The specific activity of nitrogen fixation in stem nodules is comparable to that of root nodules (Sasakawa et al. 1986; Sasakawa 1990). A red pigment, which suggests the presence of leghemoglobin, was detected in stem nodules as well as in root nodules (Yatazawa and Yoshida 1979; Yatazawa and Susilo 1980; Sasakawa et al. 1986).     

Appraisal of 15N enrichment and 15N natural abundance methods for estimating N2 fixation by understorey Acacia leiocalyx and A. disparimma in a native forest of subtropical Australia

Purpose  

It is anticipated that global climate change will increase the frequency of wildfires in native forests of eastern Australia. Understorey legumes such as Acacia species play an important role in maintaining ecosystem nitrogen (N) balance through biological N fixation (BNF). This is particularly important in Australian native forests with soils of low nutrient status and frequent disturbance of the nutrient cycles by fires. This study aimed to examine ¹⁵N enrichment and ¹⁵N natural abundance techniques in terms of their utilisation for evaluation of N₂ fixation of understorey acacias and determine the relationship between species ecophysiological traits and N₂ fixation.     

Enrichment of natural 15N abundance in frankia-infected nodules

Abstract

The enrichment of ¹⁵N in the nodules of some N₂-fixing leguminous plants is an interesting finding (Shearer et al. 1982). The extent of ¹⁵N enrichment differed depending on the plant species (Shearer et al. 1982; Yoneyama 1987) and bacterial strains (Steele et al. 1983), and in soybeans it was apparently related to the nitrogen fixation efficiency (Shearer et al. 1984)     

Nature and mechanisms of aluminium toxicity,tolerance and amelioration in symbiotic legumes and rhizobia

Recent findings on the effect of aluminium (Al) on the functioning of legumes and their associated microsymbionts are reviewed here. Al represents 7% of solid matter in the Earth’s crust and is an important abiotic factor that alters microbial and plant functioning at very early stages. The trivalent Al (Al³⁺) dominates at pH <?5 in soils and becomes a constraint to legume productivity through its lethal effect on rhizobia, the host plant and their interaction. Al³⁺ has lethal effects on many aspects of the rhizobia/legume symbiosis, which include a decrease in root elongation and root hair formation, lowered soil rhizobial population, and suppression of nitrogen metabolism involving nitrate reduction, nitrite reduction, nitrogenase activity and the functioning of uptake of hydrogenases (Hup), ultimately impairing the N₂ fixation process. At the molecular level, Al is known to suppress the expression of nodulation genes in symbiotic rhizobia, as well as the induction of genes for the formation of hexokinase, phosphodiesterase, phosphooxidase and acid/alkaline phosphatase. Al toxicity can also induce the accumulation of reactive oxygen species and callose, in addition to lipoperoxidation in the legume root elongation zone. Al tolerance in plants can be achieved through over-expression of citrate synthase gene in roots and/or the synthesis and release of organic acids that reverse Al-induced changes in proteins, as well as metabolic regulation by plant-secreted microRNAs. In contrast, Al tolerance in symbiotic rhizobia is attained via the production of exopolysaccharides, the synthesis of siderophores that reduce Al uptake, induction of efflux pumps resistant to heavy metals and the expression of metal-inducible (dmeRF) gene clusters in symbiotic Rhizobiaceae. In soils, Al toxicity is usually ameliorated through liming, organic matter supply and use of Al-tolerant species. Our current understanding of crop productivity in high Al soils suggests that a much greater future accumulation of Al is likely to occur in agricultural soils globally if crop irrigation is increased under a changing climate.     

Accumulation of cadmium and other metals in organs of plants growing around metal smelters in Japan

Abstract

It is well known that some plants can adapt to a high concentration of metals that would be lethal to other plant species and also accumulate toxic metals in their body up to a very high level (Peterson 1983). Athyrium yokoscense communities are often observed on highly polluted soils with heavy metals originating from mining or smelting facilities. A. yokoscense and some species of plants which can grow vigorously on highly polluted soils have attracted the attention of miners and investigators as indicator plants for mining areas (Honjo 1990; Nishizono et al. 1987).     

PHOSPHORUS USE EFFICIENCY FOR SYMBIOTIC NITROGEN FIXATION VARIES AMONG COMMON BEAN RECOMBINANT INBRED LINES UNDER P DEFICIENCY

This study compared the growth, nodulation, phosphorus use efficiency and nitrogen (N₂) fixation by six recombinant inbred lines (RILs) of Phaseolus vulgaris (RILs 147, 28, 83, 34, 7, and 104). These RILs were inoculated with Rhizobium tropici CIAT899 and grown in an aerated nitrogen-free nutrient solution at deficient versus sufficient phosphorous supplies (75 vs. 250 μmol P plant^?1 week^?1) in a glasshouse. Our results show that plant growth, nodulation, and symbiotic nitrogen fixation were significantly affected by P deficiency for all RILs, whereas this adverse effect was more pronounced in RILs 147, 83, 28 and 7 than in RILs 34 and 104. Under P deficiency, RILs 34 and 104 showed higher efficiency than other RILs in the use of P for their symbiotic N nutrition. It is concluded that P utilization efficiency may be a useful selection criterion for genotypic adaptation of N₂-fixing legumes to low P soils.     

Understorey biomass production and biological nitrogen fixation in an organic Apple orchard in Canterbury,New Zealand

Abstract

One of the basic requirements for sustainable management of soils is to ensure that soil fertility is maintained in a productive state and conditions so as to enable the soil to continue to provide viable economic yields with minimum degradation of soil quality and quantity. The practice of supplying nitrogen to fruit trees from biological nitrogen fixation by pasture legumes in the understorey vegetation of orchards is a sustainable means of maintaining soil fertility. Quantitative field measurements of amounts of biomass production and biological nitrogen fixation by three different kinds of understorey vegetation in an organic apple orchard in Canterbury, New Zealand was conducted over a period of two years. Results obtained showed that understorey herbage biomass production varied from 8 to 12 t ha^‐1 and biological nitrogen fixation varied from 118 to 126 kg N ha^‐1 over the period of two years. Nitrogen fixation was significantly correlated with clover dry matter production. Results were affected by seasons and understorey management practices.     

土壤条件影响刺槐固氮的回归模型

刺槐（Robinia pseudoacacia L.)根瘤的固氮能力在四川盆地以中性、弱钙质和微酸性土壤为高，强酸性和强钙质土壤上低。土壤条件对固氮能力的影响可用多元回归方程来表达。在方程拟合过程中，作者提出了非线性因子的线性化转换法，并用电脑模拟固氮因素的交互作用。42种试验土壤中，有效磷、以及它们分别与CO2（生物活性）、全磷的结合，是影响固氮的主要因素；其次pH与CaCO3、全磷中的有效磷与有效Mo的配合，对固氮亦有重要贡献。方程可以评价和预测共生体在不同土壤条件的固氮潜力。     

Symbiotic effectiveness of Bradyrhizobium japonicum in acid soils can be predicted from their sensitivity to acid soil stress factors in acidic agar media

In acid soil, low pH, reduced availability of nutrients, and toxicity of Al and Mn limit plant growth and the survival and effectiveness of rhizobia. The symbiosis between legumes and rhizobia is particularly sensitive to acid soil stress. A pot experiment evaluated whether Bradyrhizobium japonicum strain growth on acidic agar media would predict ability to colonize the rhizosphere and form effective nodules in acidic soils. Three Indonesian strains of B. japonicum with similar effectiveness at neutral pH in sand culture but with different tolerance of acid soil stress factors in agar media, and an acid-tolerant commercial strain (CB1809) of comparable effectiveness, were tested in three acid soils using the Al tolerant soybean (Glycine max cv PI 416937). At 7 days after inoculation all strains had achieved large rhizosphere populations, but by day 14 the rhizosphere population of the acid-sensitive strain had decreased, while the more acid-tolerant strains increased. The acid-tolerant strains had significantly greater nodulation and symbiotic effectiveness than plants inoculated with the acid-sensitive strain. Laboratory prescreening of B. japonicum for acid, Al and Mn tolerance in acid media successfully identified strains which were symbiotically competent in low pH soils.     

The effect of acidity on the distribution and symbiotic efficiency of rhizobia in Lithuanian soils

The distribution and symbiotic efficiency of nodule bacteria Rhizobium leguminosarum_bv. trifolii F., Sinorhizobium meliloti D., Rhizobium galegae L., and Rhizobium leguminosarum bv. viciae F. in Lithuanian soils as dependent on the soil acidity were studied in the long-term field, pot, and laboratory experiments. The critical and optimal pH values controlling the distribution of rhizobia and the symbiotic nitrogen fixation were determined for every bacterial species. The relationship was found between the soil pH and the nitrogen-fixing capacity of rhizobia. A positive effect of liming of acid soils in combination with inoculation of legumes on the efficiency of symbiotic nitrogen fixation was demonstrated.     

Effect of aluminum on callose synthesis in root tips of tea (Camellia sinensis L.) plants

Aluminum (Al) toxicity is a major factor limiting yield production on acid soils (Foy 1983). The initial symptom of Al toxicity in many plants is manifested by the inhibition of root elongation (Ownby and Popham 1990; Llugany et al. 1994; Sasaki et al. 1994; Horst et al. 1997), which occurs during a very short period of time after exposure to Al (Llugany et al. 1994; Staß and Horst 1995). In a large number of recent reports, it was shown that the root apex plays a major role in the Al-sensitivity and response mechanisms (Zhang et al. 1994; Sasaki et al. 1997; Sivaguru and Horst 1998). However, it is interesting to note that stimulatory effects of Al on the growth of plants have also been reported in some studies (Chenery 1955; Konishi et al. 1985; Huang and Bachelard 1993; Osaki et al. 1997). In tea plant (Camellia sinensis L.) a stimulatory effect of Al on the growth was also demonstrated in some experiments, using intact plant (Chenery 1955; Konishi et al. 1985), cultured roots (Tsuji et al. 1994), and pollen tubes (Yokota et al. 1997). The growth of tea roots was typically more stimulated than that of shoots by Al (Konishi et al. 1985). It was assumed that Al effects might be due to the amelioration of phosphorus absorption (Konishi et al. 1985), secretion of malic acid from roots to dissolve aluminum phosphate in the rhizosphere (Jayman and Sivasubramaniam 1975), stimulation of growth of microorganisms on the root surface (Konishi 1990) or replacement of some functions of boron (Konishi 1992; Yokota et al. 1997). However, the stimulatory effects of Al on tea plant growth have not yet been el ucidated.

The formation of callose (1,3-β-glucan) has been reported as a common plant response to a variety of stresses, as well as mechanical, biophysical, chemical, and biological injury (Jaffe and Leopold 1984; Zhang et al. 1994). Increased synthesis of callose has been observed upon exposure to excess amounts of some elements, such as boron (McNairn and Currier 1965), cobalt, nickel, zinc (Peterson and Rauser 1979), and manganese (Wissemeier and Horst} 1987, 1992). Callose synthesis was also induced by Al in the roots of Triticum aestivum (Zhang et al. 1994) and Zea mays (Horst et al. 1997; Sivaguru and Horst 1998), suspension-cultured cells of Glycine max (Staß and Horst 1995), and protoplasts of Avena sativa (Schaeffer and Walton 1990) and Zea mays (Wagatsuma et al. 1995). Induction of callose synthesis in roots seems to be a very rapid physiological indicator of Al-induced injury or genotypical differences in Al sensitivity (Wissemeier and Horst 1992; Zhang et al. 1994; Horst et al. 1997). Nevertheless, Al-induced callose synthesis in tea plant, whose growth is stimulated by suitable Al concentrations, has not been described yet. Therefore, to elucidate the physiological basic effects of Al on tea plant, callose synthesis affected by Al in the root tips of intact plants was analyzed in the present study.     

Reactive aluminum in the vermont soil test

Abstract

Determination of Reactive Al by extracting a soil sample with pH 4.8 NH₄ OAc (1.25 N acetate) characterizes for northern acid soils the quantity of soil acidity that must be neutralized to meet lime need and also lower the P adsorbing capacity. Extracted Al is used in conjunction with pH in 10 mM CaCl₂ to calculate the lime requirement directly. First, the amount of P fertilizer needed is approximated, based on the P intensity (Available P) determined in the same NH₄ OAc extract. Then the recommended amount is increased by a P‐fixation factor obtained from the Reactive Al measured, and decreased by a Reserve P factor derived from fluoride extractable P.

Unlike a buffer lime requirement method, which predicts lime needed to reach a target pH, the Reactive Al test estimates the quantity of acidity that must be neutralized to prevent fixation of P fertilizer by soil Al and to release P from Al‐bound sources. Attaining a particular target pH is not the primary goal. The Reserve P test measures the amount of unavailable Al phosphates that becomes partially available when lime needs are met.