| 1. |
- Bargaz, Adnane
(författare)
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Agroforestry promotes soybean yield stability and N-2-fixation under water stress
- 2015
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Ingår i: Agronomy for Sustainable Development. - : Springer Science and Business Media LLC. - 1774-0746 .- 1773-0155. ; 35, s. 1541-1549
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Tidskriftsartikel (refereegranskat)abstract
- Agroforestry systems can buffer crop performance against the impacts of climate change, particularly decreases in the availability of soil water. Nonetheless, farmers are reluctant to adopt agroforestry systems due to concerns of yield losses, predominantly in the tree-crop competitive zone. Yet little is known about crop performance in the tree-crop competitive zone under water limited conditions. We therefore studied the effect of a full season water deficit on soybean N-2-fixation, nodulation, and yield in the tree-crop zone of a mature agroforestry system. We hypothesized higher N-2-fixation yet lower but stable yield in the tree-crop zone. Rainfall reduction shelters were used to reduce available soil moisture throughout the growing season in the tree-crop competitive zone of a 27-year-old tree-based intercropping agroforestry system and a paired monoculture control plot in southern Ontario, Canada. Results show that soybean yields in the tree-crop zone were lower compared to monoculture. However, soybean yields were stable in agroforestry and only in monoculture did the rainfall reduction induce a significant decline in soybean yields. Soybeans in the tree-crop zone relied heavily on N-2-fixation to meet N demand, with a percentage of N derived from atmosphere (%Ndfa) of 91 % versus 63 % in monoculture. However, total fixed N declined significantly under rainfall reduction in both the tree-crop zone and in monoculture. Of note, soybean nodulation patterns adapted to soil moisture availability, allocating a larger proportion of nodules lower on the rooting system under water limitation. Our results demonstrate that important N pathways may be altered under water limitation. We can also expect that in areas where growing conditions are predicted to become drier in the future, yields in the tree-crop competitive zone will not be reduced further, thus increasing the viability of adopting agroforestry systems in areas affected by climatic change.
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| 2. |
- Bargaz, Adnane, et al.
(författare)
-
Discrimination against N-15 among recombinant inbred lines of Phaseolus vulgaris L. contrasting in phosphorus use efficiency for nitrogen fixation
- 2014
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Ingår i: Journal of Plant Physiology. - : Elsevier BV. - 0176-1617 .- 1618-1328. ; 171, s. 199-204
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Tidskriftsartikel (refereegranskat)abstract
- Although isotopic discrimination processes during nitrogen (N) transformations influence the outcome of N-15 based quantification of N-2 fixation in legumes, little attention has been given to the effects of genotypic variability and environmental constraints such as phosphorus (P) deficiency, on discrimination against N-15 during N-2 fixation. In this study, six Phaseolus vulgaris recombinant inbred lines (RILs), i.e. RILs 115, 104,34 (P deficiency tolerant) and 147, 83, 70 (P deficiency sensitive), were inoculated with Rhizobium tropici CIAT899, and hydroaeroponically grown with P-sufficient (250 mu mol P plant(-1) week(-1)) versus P-deficient (75 mu mol P plant(-1) week(-1)) supply. Two harvests were done at 15 (before nodule functioning) and 42 (flowering stage) days after transplanting. Nodulation, plant biomass, P and N contents, and the ratios of N-15 over total N content (N-15/Nt) for shoots, roots and nodules were determined. The results showed lower N-15/Nt in shoots than in roots, both being much lower than in nodules. P deficiency caused a larger decrease in N-15/Nt in shoots (-0.18%) than in nodules (-0.11%) for all of the genotypes, and the decrease in shoots was greatest for RILs 34 (-0.33%) and 104 (-0.25%). Nodule N-15/Nt was significantly related to both the quantity of N-2 fixed (R-2= 0.96***) and the P content of nodules (R-2= 0.66*). We conclude that the discrimination against N-15 in the legume N-2-fixing symbiosis of common bean with R. tropici CIAT899 is affected by P nutrition and plant genotype, and that the N-15/Nt in nodules may be used to screen for genotypic variation in P use efficiency for N-2 fixation. (C) 2013 Elsevier GmbH. All rights reserved.
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| 3. |
- Bargaz, Adnane
(författare)
-
Expression of a phosphate-starvation inducible fructose-1,6-bisphosphatase gene in common bean nodules correlates with phosphorus use efficiency
- 2016
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Ingår i: Journal of Plant Physiology. - : Elsevier BV. - 0176-1617 .- 1618-1328. ; 205, s. 48-56
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Tidskriftsartikel (refereegranskat)abstract
- While increased P-hydrolysing acid phosphatases (APase) activity in bean nodules is well documented under phosphorus (P) limitation, gene expression and subcellular localization patterns within the N-2-fixing nodule tissues are poorly understood. The aim of this research was to track the enzyme activity along with the intra-nodular localization of fructose-1,6-bisphosphatase (FBPase), and its contribution to P use efficiency (PUE) under symbiotic nitrogen fixation (SNF) in Phaseolus vulgaris. The FBPase transcript were localized in situ using RT-PCR and the protein activity was measured in nodules of two contrasting recombinant inbred lines (RILs) of P. vulgaris, namely RILs 115 (P-efficient) and 147 (P-inefficient), that were grown under sufficient versus deficient P supply. Under P-deficiency, higher FBPase transcript fluorescence was found in the inner cortex as compared to the infected zone of RIL115. In addition, both the specific FBPase and total APase enzyme activities significantly increased in both RILs, but to a more significant extent in RIL115 as compared to RIL147. Furthermore, the increased FBPase activity in nodules of RIL115 positively correlated with higher use efficiency of both the rhizobial symbiosis (23%) and P for SNF (14% calculated as the ratio of N-2 fixed per nodule total P content). It is concluded that the abundant tissue-specific localized FBPase transcript along with induced enzymatic activity provides evidence of a specific tolerance mechanism where N-2-fixing nodules overexpress under P-deficiency conditions. Such a mechanism would maximise the intra-nodular inorganic P fraction necessary to compensate for large amount of P needed during the SNF process. (C) 2016 Elsevier GmbH. All rights reserved.
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| 4. |
- Bargaz, Adnane, et al.
(författare)
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Faba bean variety mixture can modulate faba bean-wheat intercrop performance under water limitation
- 2021
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Ingår i: Frontiers in Agronomy. - : Frontiers Media SA. - 2673-3218. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Commercial legume varieties vary in terms of their drought tolerance when grown as sole crops, though relatively little is known about how legume variety selection affects cereal–legume intercrop performance under drought conditions. This study aims to test the hypothesis that positive rhizosphere interactions in faba bean–wheat intercrops will confer a “buffering capacity” on faba bean and wheat performance under water stress and that this effect will (i) depend on faba bean varietal selection and (ii) be enhanced with increasing faba bean varietal diversity. In a greenhouse experiment, three commercial faba bean (Vicia faba L.) varieties [Gloria (G), Alexia (A), Julia (J)] were grown in sole crop or intercropped with spring wheat (Triticum aestivum L.) under well-watered or water-stress conditions. Under intercropping, either one, two, or all three faba bean varieties were grown together with wheat to test the effect of intraspecific diversity on a cereal–legume intercrop performance. Consistent with the proposed hypothesis, we found that, under well-watered and water-stress conditions, wheat and faba bean shoot biomass production and nitrogen (N) acquisition improved with intercropping and that faba bean variety and variety mixture strongly modulated the intercropping effect. Interestingly, in both well-watered and water-stress conditions, wheat dry biomass and N accumulation were greatest in intercrops containing Gloria, while nodule number, nodule weight, and N accumulation in faba bean were greatest for intercrops containing Alexia and Julia (AJ). The effect of varietal diversity was inconsistent. Intercrops with two faba bean varieties tended to have positive or neutral effects on measured wheat and faba bean variables. However, overall performance under intercropping was generally reduced when all three faba bean varieties were planted with wheat. The effect of faba bean species diversity can buffer faba bean–wheat intercrop performance against water stress, and intercropping tended to have positive or neutral effects on the measured wheat and faba bean variables, notably with two-varietal faba bean mixtures.
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| 5. |
- Bargaz, Adnane
(författare)
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Genotypic variation of nodules' enzymatic activities in symbiotic nitrogen fixation among common bean (Phaseolus vulgaris L.) genotypes grown under salinity constraint
- 2013
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Ingår i: Symbiosis. - : Springer Science and Business Media LLC. - 0334-5114 .- 1878-7665. ; 60, s. 115-122
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Tidskriftsartikel (refereegranskat)abstract
- The effect of salt stress, under glasshouse conditions, was studied on plant biomass, nodulation, and activities of acid phosphatases (APase, EC 3.1.3.2) and trehalose 6-phosphate phosphatase (TPP, EC 3.1.3.12) in the symbiosis common bean (Phaseolus vulgaris L.)-rhizobia nodules. Four common bean recombinant inbred lines (147, 115, 104 and 83) were separately inoculated, with CIAT 899 or RhM11 strains and grown in hydroaeroponic culture. Two NaCl levels (0 and 25 mM NaCl plant(-1) week(-1) corresponding, respectively, to the control and the salt treatment) were applied and the culture was assessed during 42 days after their transplantation. The results showed that the nodulation of these lines was not affected by salinity except for the line 83 inoculated with CIAT 899, whose nodule dry weight decreased by 48.24 % compared with the corresponding controls. For the other symbiotic combinations, shoot and root biomasses were not significantly affected by salt constraint. Salinity stress generally reduced acid phosphatise and trehalose phosphate phosphatase activities in nodules that were less affected in plants inoculated with RhM11. Based on our data, it appears that nodule phosphatase activity may be involved in salinity tolerance in common beans and the levels of salt tolerance depend principally on specific combination of the rhizobial strain and the host cultivar.
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| 6. |
- Bargaz, Adnane
(författare)
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Improved Salinity Tolerance by Phosphorus Fertilizer in Two Phaseolus vulgaris Recombinant Inbred Lines Contrasting in Their P-Efficiency
- 2016
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Ingår i: Journal of Agronomy and Crop Science. - : Wiley. - 0931-2250. ; 202, s. 497-507
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Tidskriftsartikel (refereegranskat)abstract
- Legumes' sensitivity to salt is exacerbated under growth conditions requiring nitrogen fixation by the plant. Phosphorus (P) deficiency is widespread in legumes, especially common bean (Phaseolus vulgaris L). To examine the performance of P. vulgaris under salt stress conditions, a field experiment was conducted using two recombinants inbred lines (RILs) 115 (P-deficiency tolerant) and 147 (P-deficiency susceptible), grown under different salinity levels (L) (1.56, 4.78, and 8.83 dS m(-1) as LI, L2, and L3, respectively) and supplied with four P rates (0, 30, 60, and 90 kg ha(-1) P as P0, P30, P60, and P90, respectively) in order to assess the impact of P on salt tolerance. Results indicate that growing both RILs at P60 or P90 under all salinity levels (especially L1) significantly increased total chlorophyll, carotenoids, total soluble sugars, total free amino acids, and proline. Increasing P supply up to P60 under all salinity levels significantly induced higher accumulation of P, K+, Ca2+ and Mg2+ leaves in both RILs. Based on quadratic response over all locations, the maximum seed yield of 1.465 t ha(-1) could be obtained at application of P 81.0 kg ha-1 in RIL115, while seed yield of 1.275 t ha(-1) could be obtained with P rate of 78.3 kg ha(-1) in RIL147. RIL115 exhibited more salt-tolerance with positive consequence on plant biomass and grain yield stability. Improved salt tolerance through adequate P fertilization is likely a promising strategy to improve P. vulgaris salinity tolerance and thus productivity, a response that seems to be P-rate dependent.
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| 7. |
- Bargaz, Adnane, et al.
(författare)
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Intercropping of faba bean with wheat under low water availability promotes faba bean nodulation and root growth in deeper soil layers
- 2015
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Ingår i: Procedia Environmental Sciences. - : Elsevier BV. - 1878-0296. ; 29, s. 111-112
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Konferensbidrag (refereegranskat)abstract
- The symbiotically fixed N is advantageous to legumes growing under N-limiting conditions, and is also potentially beneficial for subsequent or associated non-legume crops(1, 2). However, under stressful conditions such as water limitation and low nutrient availability, legumes may lose the distinct advantage of an unlimited source of symbiotic N-2 (3, 4,) (5) Belowground niche complementarity in legume-cereal intercrops may improve resource use efficiency and adaptability to environmental constraints, but effects of water limitation on legume rooting and nodulation patterns is poorly understood. To advance our knowledge of mechanisms involved in water stress response, faba bean (Vicia faba L., FB) and wheat (Triticum aestivum L.) were grown as mono- and intercrops in soil-filled plexiglass rhizoboxes under water sufficiency (80% of field capacity; FC) and water stress (30% of FC). Water stress decreased shoot biomass in both monocropped and intercropped FB, as well as root length in monocropped FB. Intercropping increased both shoot dry weight and height of FB irrespective of water treatment, while increased root biomass and length in intercropped FB was observed only under water stress. No significant effects of crop or water treatment were found on wheat growth parameters. Intercropping increased overall nodulation (nodule number and nodule dry weight; NDW) regardless of water availability. However spatial patterns of nodulation differed between water treatments: top-15-cm NDW and number increased (27 and 33%, respectively) in sufficiently-watered intercropped FE, while NDW in the same soil layer significantly decreased (45%) in water-stressed intercropped FE. In contrast, below-15-cm NDW and number significantly increased in intercropped FE under both water levels. This enhanced nodulation in the deeper soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy that improves FB performance when exposed to water limitation in intercropping. (C) 2015 The Authors. Published by Elsevier B.V.
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| 8. |
- Bargaz, Adnane
(författare)
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Localization of phytase transcripts in germinating seeds of the common bean (Phaseolus vulgaris L.)
- 2014
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 240, s. 471-478
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Tidskriftsartikel (refereegranskat)abstract
- The work provides the first-time evidence of tissue-specific expression of a phytase gene in the germinating seeds of Phaseolus vulgaris.Phytase enzyme plays a major role in germinating seeds. It is also active during N-2 fixation within nodules of legumes. The effect of phosphorus (P) deficiency on phytase gene expression and localization in N-2-fixing root nodules has been recently studied in hydroaeroponic culture of Phaseolus vulgaris. In this study, phytase gene transcripts within the germinating seed tissues of the P-inefficient P. vulgaris recombinant inbred line RIL147 were in situ localized with a similar RT-PCR recipe as that used for nodules. Our results show that the phytase gene expression was mainly localized in the outer layers, vascular cells and parenchyma of germinating seeds whereas it was localized in the inner and middle cortex of nodules. Image analysis quantified higher fluorescence intensity of the phytase transcript signal in the seed embryo than in radicles, cotyledons or the nodule cortex. Furthermore, the phytase activity was 22-fold higher in cotyledons (43 nmol min(-1) g(-1) dry weight) than in nodules (2 nmol min(-1) g(-1) dry weight). The K (m) and V (m) values of phytase activity in cotyledons were also significantly higher than in nodules. Interestingly, the amplified sequence of cDNA phytase exhibited highest homology with the Glycine max purple acid phosphatase (NM_001289274) 90 % for germinating seed as compared to nodule phytase cDNA displaying 94 % homology with the Glycine max phytase (GQ422774.1). It is concluded that phytase enzymes are likely to vary from seeds to nodules and that phytase enzymes play key roles in the use of organic P or N-2 fixation, as it is well known for germination.
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| 9. |
- Bargaz, Adnane
(författare)
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Localization of the Bacillus subtilis beta-propeller phytase transcripts in nodulated roots of Phaseolus vulgaris supplied with phytate
- 2014
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Ingår i: Planta. - : Springer Science and Business Media LLC. - 0032-0935 .- 1432-2048. ; 239, s. 901-908
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Tidskriftsartikel (refereegranskat)abstract
- Soil organic phosphorus (Po) such as phytate, which comprises up to 80% of total Po, must be hydrolyzed by specific enzymes called phytases to be used by plants. In contrast to plants, bacteria, such as Bacillus subtilis, have the ability to use phytate as the sole source of P due to the excretion of a beta-propeller phytase (BPP). In order to assess whether the B. subtilis BPP could make P available from phytate for the benefit of a nodulated legume, the P-sensitive recombinant inbred line RIL147 of Phaseolus vulgaris was grown under hydroaeroponic conditions with either 12.5μM phytate (C6H18O24P6) or 75μmol Pi (K2HPO4), and inoculated with Rhizobium tropici CIAT899 alone, or co-inoculated with both B. subtilis DSM 10 and CIAT899. The in situ RT-PCR of BPP genes displayed the most intense fluorescent BPP signal on root tips. Some BPP signal was found inside the root cortex and the endorhizosphere of the root tip, suggesting endophytic bacteria expressing BPP. However, the co-inoculation with B. subtilis was associated with a decrease in plant P content, nodulation and the subsequent plant growth. Such a competitive effect of B. subtilis on P acquisition from phytate in symbiotic nitrogen fixation might be circumvented if the rate of inoculation were reasoned in order to avoid the inhibition of nodulation by excess B. subtilis proliferation. It is concluded that B. subtilis BPP gene is expressed in P. vulgaris rhizosphere.
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| 10. |
- Bargaz, Adnane, et al.
(författare)
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Nodulation and root growth increase in lower soil layers of water-limited faba bean intercropped with wheat
- 2016
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Ingår i: Journal of Plant Nutrition and Soil Science. - : Wiley. - 1436-8730 .- 1522-2624. ; 179, s. 537-546
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Tidskriftsartikel (refereegranskat)abstract
- Below-ground niche complementarity in legume-cereal intercrops may improve resource use efficiency and root adaptability to environmental constraints. However, the effect of water limitation on legume rooting and nodulation patterns in intercropping is poorly understood. To advance our knowledge of mechanisms involved in water-limitation response, faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were grown as mono- and intercrops in soil-filled plexiglass rhizoboxes under water sufficiency (80% of water-holding capacity) and water limitation (30% of water-holding capacity). We examined whether intercropping facilitates below-ground niche complementarity under water limitation via interspecific root stratification coupled with modified nodulation patterns. While no significant treatment effects were measured in intercropped wheat growth parameters, water limitation induced a decrease in shoot and root biomass of monocropped wheat. Likewise, shoot biomass and height, and root length of monocropped faba bean significantly decreased under water limitation. Conversely, water limitation stimulated root biomass of intercropped faba bean in the lower soil layer (15-30 cm soil depth). Similarly, total nodule number of faba bean roots as well as nodule number in the lower soil layer increased under intercropping regardless of water availability. Under water limitation, intercropping also led to a significant increased nodule biomass (48%) in the lower soil layer as compared to monocropping. The enhanced nodulation in the lower soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy when intercropped with wheat, which improves water-limited faba bean performance.
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