Rhizobia induces nitrogen-fixing nodules in legumes used in agricultural production,providing a direct source of combined nitrogen to leguminous crops.Small peptides,such as CLAVATA3/EMBRYO SURROUNDING REGION peptides(...Rhizobia induces nitrogen-fixing nodules in legumes used in agricultural production,providing a direct source of combined nitrogen to leguminous crops.Small peptides,such as CLAVATA3/EMBRYO SURROUNDING REGION peptides(CLE),are known to regulate the formation and development of nitrogen-fixing nodules in legumes.Root meristem growth factor(RGF)peptides from Medicago truncatula not only regulate root develop-ment but also modulate nodulation symbiosis with Sinorhizobium meliloti.However,the impact of RGF peptides from one leguminous species on the others remains unclear.In this study,we investigate the effects of the RGF family peptide MtRGF6p from M.truncatula on nodulation symbiosis and root development in Lotus japonicus.The MtRGF6 gene is predominantly expressed in the root nodules of M.truncatula and shows low identity with RGF homologous genes from L.japonicus.The gene promoter is active in the primordia of root nodules and lat-eral roots,as well as in young nodules and roots,and the meristem,infection,and nitrogen-fixing regions of the mature nodule.Chemically synthesized MtRGF6p promoted primary root growth in M.truncatula but sup-pressed the growth of L.japonicus primary roots.The peptide negatively affected the initiation of nodule primor-dia,the formation of infection threads,and nodulation in both legumes,with a low dosage showing effects on L.japonicus compared to M.truncatula.These results suggest that the MtRGF6 peptide from M.truncatula may serve as an inter-species signal affecting the root organ development of L.japonicus.展开更多
Sesbania rostrata is wellknown for its stem nodulation, but the roles of stem nodulation in root nodulation and adaptation of S. rostrata to Pb/Zn-enriched tailings environment has been poorly understood. We investiga...Sesbania rostrata is wellknown for its stem nodulation, but the roles of stem nodulation in root nodulation and adaptation of S. rostrata to Pb/Zn-enriched tailings environment has been poorly understood. We investigated the effects of inoculating （with stem nodule treatment） and non-inoculating （without stem nodule treatment） Azorhizobium caulinodans on the growth, root nodulation, and N fixation of S. rostrata grown on three different types of soil substrata： Pb/Zn tailings, garden soil amended tailings, and garden soil. The results showed that plant height, stem basal diameter, biomass, chlorophyll content, nitrogen content and N-accumulation per plant were 2.3%-4.9%, 2.2%-7.7%, 27.8%-72.2%, 17.1%-23.5%, 12.3%-34.2%, and 43.1%-131.2%, respectively, higher in treatments with stem nodule than those without stem nodule for the same soil substrate. With respect to soil substrata, all measurements had consistently higher values in tailings than in amended tailings and garden soil, indicating that the poorer the soil condition, the greater the contribution of stem nodule. In contrast, the number and fresh weight of root nodules on plants without stem nodule were 6.9-11.6 times and 5.8-29.0 times higher than those with stem nodule, respectively, especially with respect to the plants grew on Pb/Zn tailings. In general, stem nodulation favored plant growth and nitrogen fixation of S. rostrata, but suppressed root nodulation. With the ability of stem and root nodulation, S. rostrata can be used as a pioneer plant species for remediation of Pb/Zn tailings.展开更多
As an important food crop and oil crop, soybean(Glycine max [L.] Merr.) is capable of nitrogen-fixing by root nodule. Previous studies showed that GmNMH7, a transcription factor of MADS-box family, is associated with ...As an important food crop and oil crop, soybean(Glycine max [L.] Merr.) is capable of nitrogen-fixing by root nodule. Previous studies showed that GmNMH7, a transcription factor of MADS-box family, is associated with nodule development, but its specific function remained unknown. In this study, we found that GmN MH7 was specifically expressed in root and nodule and the expression pattern of GmNMH7 was similar to several genes involved in early development of nodule(GmENOD40-1, GmENOD40-2, GmNFR1 a, GmNFR5 a, and GmNIN) after rhizobia inoculation. The earlier expression peak of GmNMH7 compared to the other genes(GmENOD40-1, GmENOD40-2, GmNFR1 a, GmNFR5 a, and GmNIN) indicated that the gene is related to the nod factor(NF) signaling pathway and functions at the early development of nodule. Over-expression of GmNMH7 in hairy roots significantly reduced the nodule number and the root length. In the transgenic hairy roots, overexpression of GmN MH7 significantly down-regulated the expression levels of GmE NOD40-1, GmE NOD40-2, and GmN FR5α. Moreover, the expression of GmNMH7 could respond to abscisic acid(ABA) and gibberellin(GA_3) treatment in the root of Zigongdongdou seedlings. Over-expressing GmNMH7 gene reduced the content of ABA, and increased the content of GA_3 in the positive transgenic hairy roots. Therefore, we concluded that GmNMH7 might participate in the NF signaling pathway and negatively regulate nodulation probably through regulating the content of GA_3.展开更多
The symbiotic matching for nodulation of Bradyrhizobium japonicum strains is a synergy of multi-proteins and plays a key role in symbiotic nitrogen fixation in nature. Studies on mechanism of symbiotic matching are si...The symbiotic matching for nodulation of Bradyrhizobium japonicum strains is a synergy of multi-proteins and plays a key role in symbiotic nitrogen fixation in nature. Studies on mechanism of symbiotic matching are significant in both theory and practice. In this paper, B. japonicum USDA110-A with high symbiotic matching with high-oil content soybean cultivar Suinong 20 and B. japonicum 2178 with low symbiotic matching were selected for proteomic to reveal mechanism of different symbiotic nodulation. The results showed that the amount and categories of proteins identified in this test were different when the two strains were treated by symbiotic nodulation. There were 10 up-regulated proteins and 5 down-regulated proteins with significant difference for B. japonicum USDA110-A. Proteins associated with nodulation and metabolism of energy and material, which were propitious to symbiotic nodulation, were all up-regulated, such as PHDPS synthase, metal-dependent phosphohydrolase, glycosyl transferase family. In contrast, only 5 up-regulated and 7 down-regulated differential proteins were detected in B. japonicum 2178. Molecular chaperones and defensive proteins, which influence the folding of nascent polypeptide chains and the active of azotase were down-regulated. To a certain extent, the different responses of B. japonicum to daidzein were one of the most important reasons that cause varieties in symbiotic matching ability.展开更多
Competitiveness for nodulation of Bradyrhizobium japonicum strains plays a key role in symbiotic nitrogen fixation. In order to reveal the difference in competitiveness, B. japonicum 4534 with high competitiveness and...Competitiveness for nodulation of Bradyrhizobium japonicum strains plays a key role in symbiotic nitrogen fixation. In order to reveal the difference in competitiveness, B. japonicum 4534 with high competitiveness and B. japonicum 4222 with low competitiveness for nodulation were analyzed by proteomic technique. The results showed that differential proteins were fewer when two strains were treated with just daidzein. Only 24 and 10 differential proteins were detected with an up-regulated rate of 58 and 40% in B. japonicum 4534 and B. japonicum 4222, respectively. However, more differential proteins were detected upon treatment with daidzein and mutual extracellular materials simultaneously. There were 78 differential proteins detected in B. japonicum 4534 with 43 being up-regulated and 35 being down-regulated. These differential proteins, such as metabolism-related proteins, transporters, transcription-related proteins, translation-related proteins, and flagellin, were found to be associated with nodulation process. 25 up-regulated and 22 down-regulated proteins were detected in B. japonicum 4222. Some of these proteins were not related to nodulation. More differential proteins associated with nodulation in B. japonicum 4534 may be the reason for its high competitiveness. The results can provide a guide to the selection and inoculation of effective strains and are significant to biological nitrogen fixation.展开更多
Triple Super Phosphate, TSP fertilizer, was applied @ 80 kg·ha^-1 as the source of phosphorous on six months old polybag seed- lings of Albizia chinensis, Albizia saman and Pongamia pinnta in nursery beds in Bang...Triple Super Phosphate, TSP fertilizer, was applied @ 80 kg·ha^-1 as the source of phosphorous on six months old polybag seed- lings of Albizia chinensis, Albizia saman and Pongamia pinnta in nursery beds in Bangladesh. The effects of P-fertilizer on seedling growth and nodulation were comparcd to that of seedlings grown in unfertilized soil or in control at different harvesting intervals. The study revealed that, seedling growth was enhanced significantly with the application of P-fertilizer. The growth was found more pronounced in cases of A. saman and P. pinnata, whereas it was not noticeable and showed depressed growth in case of A. chinensis. The study also suggests that nodulation in terms of nodule number and size was also increased significantly with P-fertilization except in case ofP. pinnata, where higher harvesting intervals lowered the nodulation performance of that species展开更多
A study was conducted to test the influence of different inorganic fertilizers （phosphorous and potassium） on the nodulation and growth of Dalbergia sissoo grown in the nursery. Before seeds sowing, different combin...A study was conducted to test the influence of different inorganic fertilizers （phosphorous and potassium） on the nodulation and growth of Dalbergia sissoo grown in the nursery. Before seeds sowing, different combinations of P, K fertilizers were incorporated with the nutrient-deficient natural forest soils, and then amended with cowdung （soil： cowdung = 3：1）. Nodulation status （nodule number, shape, fresh weight, dry weight and color） in the roots and the plant growth parameters （length of shoot and root, collar diameter, fresh and dry weight of shoot and root） were recorded 60 days after seeds sowing. Nodulation status and growth of the plants varied significantly （P〈0.05） in the soils amended with fertilizers in comparison to the control. The highest nodule number （62）, fresh （0.50 g） and dry （0.07 g） weights were recorded with the dose of PK at the rate of 160 kg/hm2. Nodule shape and color also varied widely in different treatments. In case of plant growth parameters, shoot and root length, collar diameter, fresh and dry weight of the plants took on a significant difference （P〈0.05） among various combination of fertilizers. From the study, it is revealed that PK at the rate of 160 kg/hm^2 fertilizer with soil and cowdung mixture （soil： eowdung = 3：1） is recommended for optimum growth and nodule formation of D. sissoo in degraded soils at a nursery level.展开更多
Bradyrhizobia are known symbiotic partners of soybean. However, some soybean cultivars restrict nodulation by some Bradyrhizobium bacterial strains. These restrictions are related to compatibility between the Rj genes...Bradyrhizobia are known symbiotic partners of soybean. However, some soybean cultivars restrict nodulation by some Bradyrhizobium bacterial strains. These restrictions are related to compatibility between the Rj genes of soybean cultivars and nodulation types of inoculated bacteria. The objective of this study was to determine nodulation incompatibility of Type B strains with Rj3 soybean cultivars. Newly isolated B. elkanii strains BLY3-8 and BLY6-1 from Myanmar and specific strain Bradyrhizobium elkanii USDA33, which are incompatible with Rj3 soybean cultivars, and B. japonicum USDA110 were used as inoculants to check compatibility or incompatibility with Rj3 soybean cultivars. Nitrogen fixation activity was measured by the acetylene reduction method. Ethylene concentration (reduction of acetylene) was determined by flame ionization gas chromatography. According to the inoculation test results, USDA110 was compatible with all soybean cultivars because it formed effective nodules (Figure S1 in Appendix) and possessed nitrogenase activity. Similarly, B. elkanii strains BLY3-8, BLY6-1, and USDA33 were highly compatible with non-Rj and Rj4-gene harboring soybean cultivars because they had the ability to form functional nodules and possessed nitrogenase activity. Inversely, BLY3-8, BLY6-1, and USDA33 were incompatible with Rj3 soybean cultivars because they produced ineffective nodules. Consequently, the ratio of ineffective nodule number to total nodule number was >0.5. Therefore, nodule formation by the newly isolated B. elkanii strains BLY3-8 and BLY6-1 was restricted by the Rj3 soybean cultivars potentially making them useful as specific strains to detect the Rj3 gene in soybean cultivars.展开更多
Groundnut (Arachis hypogaea), cowpea (Vigna unguiculata) and soybean (Vigna radiata) are the main food legumes grown in Cote d’Ivoire and the localities of Haut-Sassandra. These legumes are highly valued for their nu...Groundnut (Arachis hypogaea), cowpea (Vigna unguiculata) and soybean (Vigna radiata) are the main food legumes grown in Cote d’Ivoire and the localities of Haut-Sassandra. These legumes are highly valued for their nutritional, agronomic and economic value. Groundnut, cowpea and soybean are the main food legumes grown in Cote d’Ivoire and in the localities of Haut-Sassandra. On the other hand, Ivorian soils are characterized by a tendency towards acidification and a decrease in the content of nutrients such as phosphorus and nitrogen which have a direct impact on the products. To restore soil fertility, farmers use mineral fertilization. However, this fertilization has an influence on the nodulation of these legumes. The study took place at Jean Lorougnon University. We adopted a completely random experimental block device. The parameters measured included the number of nodules, the length and weight of the plant, the length and weight of the root system. Our results showed that mineral fertilization reduced the nodulation capacity of legumes. However, a small dose of phosphorus ( g) would be required for early growing legumes.展开更多
Vigna unguiculata(L.) Walp (cowpea) is a tropical legume of very high nutritive and economic values. A laboratory experiment was conducted to evaluate the BNF (biological nitrogen fixation) efficiency of 4 strains of ...Vigna unguiculata(L.) Walp (cowpea) is a tropical legume of very high nutritive and economic values. A laboratory experiment was conducted to evaluate the BNF (biological nitrogen fixation) efficiency of 4 strains of Bradyrhizobium sp. (VUXYI, VUIEI, VUMDSI and VUIDI). From the results obtained these strains were classified into efficiency groups, with VUIDI being the most efficient and VUXYI the least efficient.The effect of inoculation was tested on 2 cowpea varieties in a field experiment. Remarkable increases in nodulation biomass and crop yield were observed. An increase from 58% to 81% in dry seed was obtained for the two varieties. A significance test revealed a significantly positive correlation between nodulation and biomass.展开更多
An experiment was conducted to assess the effect of Phosphorous （P） fertilizer （i.e. TSP or triple super phosphate @ 80 kg/hm^2） on seedling growth and nodulation capabilities of three potentially important agrofo...An experiment was conducted to assess the effect of Phosphorous （P） fertilizer （i.e. TSP or triple super phosphate @ 80 kg/hm^2） on seedling growth and nodulation capabilities of three potentially important agroforestry tree species （Acacia auriculiformis, Albizia lebbeck and Albizia procera） of Bangladesh. The study was conducted in nursery beds with six-month-old polybag seedlings ofA. auriculiformis, A. lebbeck and A. procera. The effects of P fertilizer on seedling growth and nodulation were compared with that of the seedlings grown in control （i.e. unfertilized soil）. The observations revealed that the seedling growth was enhanced significantly with the application of P fertilizer. The growth was found more pronounced in A. auriculiformis, whereas it was not apparent and shows depressed growth in case ofA. lebbeck. The study also suggests that the nodulation in terms of nodule number and size was also increased significantly with the application of P fertilizer.展开更多
Effects of inoculation of Rhizobium suspension on nodulation and plant growth were examined withAlbizzia procera, Albizzia lebbeck and Leucaena leucocephala seedlings grown on sterilized and non-sterilizedsoil media. ...Effects of inoculation of Rhizobium suspension on nodulation and plant growth were examined withAlbizzia procera, Albizzia lebbeck and Leucaena leucocephala seedlings grown on sterilized and non-sterilizedsoil media. Inoculation resulted in nodule number increases of 28.6, 29.02 and 23.9 times in sterilized soiland 3.4, 3.6 and 3.27 times in non-sterilized soil for A. parocera A. lebbeck and L. leucocephala seedlingsrespectively. Total dry mass increased by 127.6%, 66.7% and 60.7% in sterilized soil and 100%, 95.5%and 52.65% in non-sterilized soil for these three legume trees, respectively, after a period of two months.Significalltly high inoculation responses of root length, root diameter, collar diameter, shoot length, and drymass of root, shoot, leaves and nodules were also observed in both sterilized and non-sterilized soil media ascompared to respective control treatments. The response to inoculation was strong in sterilized and modestin non-sterilized soils. The significantly higher response to Rhizobium inoculation over control in all thespecies tested suggested that application of Rhizobium greatly enhanced plant growth, nodulation, biomassproduction and nitrogen-fixing activity of the nodules.展开更多
Soybean(Glycine max[L.]Merr.)is a food and oil crop whose growth and yield are influenced by root and nodule development.In the present study,Gm NMHC5 was found to promote the formation of nodules in overexpressing mu...Soybean(Glycine max[L.]Merr.)is a food and oil crop whose growth and yield are influenced by root and nodule development.In the present study,Gm NMHC5 was found to promote the formation of nodules in overexpressing mutants.In contrast,the number of nodules in Gmnmhc5 edited with CRISPR/Cas9 decreased sharply.In 35 S:Gm NMHC5 mutants,expression levels of genes involved in nodulation were significantly up-regulated.Both in vitro and in vivo biochemical analyses showed that Gm NMHC5 directly interacted with Gm GAI(a DELLA protein),and the content of gibberellin 3(GA_(3))in overexpressing mutants was lower than that in the wild type.These results revealed that Gm NMHC5 participates in the classical GA signaling pathway,and may regulate the content of GA_3 to match the optimal concentration required for nodule formation,thereby promoting nodulation by directly interacting with Gm GAI.A model illustrating the mechanism by which Gm NMHC5 promotes soybean nodulation is presented.展开更多
Nitrogen(N) is an essential macronutrient for plant growth and productivity. Leguminous plants establish symbiotic relationships with nitrogen-fixing rhizobial bacteria to use atmospheric dinitrogen gas to meet high N...Nitrogen(N) is an essential macronutrient for plant growth and productivity. Leguminous plants establish symbiotic relationships with nitrogen-fixing rhizobial bacteria to use atmospheric dinitrogen gas to meet high N demand under low-N conditions. Nodule formation and N fixation are energy-consuming processes and are inhibited by nitrate present in the environment. Previous studies in model leguminous plants characterized NIN-LIKE PROTEIN(NLP) proteins that mediate nitrate control of root nodule symbiosis, but the mechanism by which nitrate regulates soybean root nodules via NLP remains unclear. In the soybean genome we found four homologs of AtNLP7, named GmNLP7a–GmNLP7d. We showed that the expression of GmNLP7s is responsive to nitrate but not to rhizobial infection and localized GmNLP7a to the nucleus. Downregulation of GmNLP7s increased nodule number, and overexpression of GmNLP7a(GmNLP7aOE) reduced nodule number regardless of nitrate availability, suggesting a negative role for GmNLP7s in nodulation. Nitrogenase activity in the GmNLP7aOE line was comparable to that of the wild type, indicating that GmNLP7a does not affect mature nodule activity. Overexpression of GmNLP7a downregulated the expression of GmNIN1a and GmENOD40-1. GmNLP7a interacted with GmNIN1a via the PB1domain. Our results reveal a new regulator of GmNLP7 in nodulation and a molecular mechanism by which nitrate affects nodule number in soybean.展开更多
The study was carried out on the impact assessment of the form and nature of the different nitrogen sources used in culture on growth and nodulation of pigeon pea (Cajanus cajan (L.) Millsp) during 3 months of observa...The study was carried out on the impact assessment of the form and nature of the different nitrogen sources used in culture on growth and nodulation of pigeon pea (Cajanus cajan (L.) Millsp) during 3 months of observation on sandy soil of Mount Amba (at the University of Kinshasa in the Democratic Republic of Congo). Height and collar diameter growth, underground and total biomass dry weight, number and dry pea nodules and nodulation index have been evaluated at 4, 6, 8, 10 and 12 weeks of growth to assess the response of the legume to mineral nitrogen and organic nitrogen from chickens manure and pig feces. After observations, it appears that all the treatments soil showed different effects on growth and nodulation of pigeon pea. Therefore, only the soil received 1 kg of pig feces stimulated (p ≤ 0.05) the development of pigeon pea which resulted in good growth (nodulation 116.8 nodules and nodulation index of 5.0) and biomass production (25.3 gr per plant) while the addition of chicken manure, whatever the dose, reduced them.展开更多
A total of 110 strains of nodule bacteria was isolated from plants Onobrychis transcaucasica and Onobrychis chorassanica. Nodulation study of bacteria in both Onobrychis plant species in microvegetation experiment gav...A total of 110 strains of nodule bacteria was isolated from plants Onobrychis transcaucasica and Onobrychis chorassanica. Nodulation study of bacteria in both Onobrychis plant species in microvegetation experiment gave a very low nodulation on plant roots. The intensive nodulation of Onobrychis plants was recorded in vegetation experiment and for Onobrychis transcaucasica the efficiently-nodulating strains were found OT102, OT103, OT117, OT121, OT130, OT136, ОT139, ОT140, while for Onobrychis chorassanica plants—ОC106, ОC107, ОC109, ОC112, ОT103, ОT117 and ОT123 strains. Nucleotide sequencing of the 16S rRNA gene and BLAST analysis showed that nodule bacteria of Onobrychis plants were related to Rhizobium, Burkholderia, Enterobacter and Pantoea genera. It has been shown a possibility of growing up of Onobrychis plants at minimal additional moisture of sabulous soils in the Kyzyl Kum Desert, creating artificial pastures and thereby immobilizing the desert blown sands.展开更多
Soybean (Glycine max L.) plays an essential role in human nutrition as a protein source, and in plant nutrition as a N source. The rate of N fixation varies depending on the cultivars and compatibility between the ino...Soybean (Glycine max L.) plays an essential role in human nutrition as a protein source, and in plant nutrition as a N source. The rate of N fixation varies depending on the cultivars and compatibility between the inoculated Rhizobium strain and the host cultivar. Characterizing the nodulation regulatory (Rj) genes is necessary to determine the compatibility of cultivars and Rhizobium strains. Rj genes were previously identified based on inoculation tests and PCR analyses. The six cultivars Yezin-3, Yezin-7, Yezin-11, Shan Seine (Local), Madaya (Local), and Hinthada (Local) were identified as harboring the Rj4 gene. Two cultivars, Yezin-6 and Yezin-8, were classified as non-Rj-gene harboring. Two other cultivars, Yezin-9 and Yezin-10, were identified as Rj3- and Rj2Rj3-gene harboring, respectively. Ours is the first report on Rj3- and Rj2Rj3-gene harboring cultivars in Myanmar. We evaluated Myanmar soybean cultivars for symbiotic effectiveness, relying on the standard strain Bradyrhizobium japonicum USDA110. In our first experiment, the soybean cultivar Yezin-11 (Rj4) showed the highest N fixing potential. Based on their potential for fixing N and nodulation, the top six soybean cultivars were Yezin-11 (Rj4), Yezin-9 (Rj3), Yezin-6 (non-Rj), Yezin-8 (non-Rj), Yezin-3 (Rj4) and Yezin-10 (Rj2Rj3). These cultivars were selected for a second experiment, which revealed that the N fixation, nodulation, and plant growth of Yezin-11 (Rj4) *Corresponding author. A. Z. Htwe et al. 2800 were superior to the other cultivars. We conclude that Yezin-11 (Rj4) is the most efficient cultivar for nodulation and N fixation when inoculated with B. japonicum USDA110.展开更多
The purpose of this research was to evaluate the nodulation potential of 31 Argentinean soybean commercial cultivars. Those with the highest nodulation capacity response developed twice the amount of nodules than the ...The purpose of this research was to evaluate the nodulation potential of 31 Argentinean soybean commercial cultivars. Those with the highest nodulation capacity response developed twice the amount of nodules than the low nodulating ones, which is the variation contained in soybean genotypes. Furthermore, this was not due to bacterial promiscuity, since the response was independent of the bradyrhizobia strain inoculated. The ability of cultivars to develop a larger number and biomass of nodules was unrelated with the maturity group they belong to and also was not a response to quorum sensing effects. Our results suggest that breeding programs can be aimed at improving the nodulation capacity of soybean and that cultivars from different maturity groups can be a source of nodulation QTLs.展开更多
Legumes, in symbiotic association with Rhizobia, are able to fix atmospheric N. Six local lima bean (Phaseolus lunatus) cultivars were grown under rainfed conditions in a coastal savannah environment. Objectives of th...Legumes, in symbiotic association with Rhizobia, are able to fix atmospheric N. Six local lima bean (Phaseolus lunatus) cultivars were grown under rainfed conditions in a coastal savannah environment. Objectives of the study were to evaluate the nodulation and fixed atmospheric N levels of the six local lima bean cultivars using both the 15N isotope dilution method and N difference method (NDM). The linear relationship between fixed atmospheric N estimated using the 15N isotope dilution method and NDM, was also assessed. The experiment was arranged in a randomized complete block design (RCBD) in three replicates with seven treatments, comprising six lima bean cultivars (B1, B2, B3, B4, B5 and B6) and the early maturing local maize variety, “Doke”, as the reference crop. Total, effective nodules (EN) and non-effective nodules (NEN) were determined on 42 and 56 days after planting (DAP). The 15N isotopic dilution method and NDM were used to quantify the fixed atmospheric N by the lima bean cultivars on 60 DAP. Effective root nodules per plant (EN) on 56 DAP ranged from 0.71 to 1.22, with the lima bean cultivar B4 having the highest value and cultivars B2 and B5 having the lowest value of EN, respectively. Similarly on 56 DAP, the lima bean cultivar B4 had the highest NEN value while cultivars B1, B2 and B5 had the lowest NEN value of 0.71 per plant. The mean fixed atmospheric N was 8.98 kg·ha-1, based on the 15N isotope dilution method, which was lower than 10.13 kg·ha-1 of fixed atmospheric N determined using NDM. The linear relationship between fixed atmospheric N estimated using the 15N isotope dilution method and that estimated using the NDM, was positive but of average quality as the R2 value was 0.56. Consequently, the linear model obtained from this relationship is moderate as 56% of the data used for the linear regression analysis were accounted for by the linear regression model developed. However, NDM could be used for fast screening to select lima bean cultivars for a more detailed study to identify cultivars with promising fixed atmospheric N capabilities. Generally, results of the study provide opportunities for designing breeding and other agronomic programmes for enhancing the productivity and N-fixing capacity of local lima beans in the coastal savannah environment.展开更多
Soybean [<em>Glycine max</em> (L.) Merrill] seed yields in the northern United States may increase with the application of fertilizers;however Nitrogen (N) may decrease root nodulation. This study was cond...Soybean [<em>Glycine max</em> (L.) Merrill] seed yields in the northern United States may increase with the application of fertilizers;however Nitrogen (N) may decrease root nodulation. This study was conducted to understand the impact of N and sulfur (S) fertilization on soybean nodulation, plant, shoot and root biomass. Two cultivars were planted in experiments across ten site-years during 2015-2016. Plant observations took place at the V4 and R4 soybean growth stages. There were 41% more nodules per plant at R4 compared to V4 (38.3 vs 27.2 nodules, respectively). Cultivars responded differently to N and S fertilizer. The nodules per plant between the cultivars (30.3 vs 24.4) were different as well as the percent medium and large-sized nodules, which indicates the need to evaluate additional genotypes. Adding N decreased root nodulation (from 31.8 to 23.7 nodules per plant) and decreased nodule size but had no effect on plant, shoot or root mass. Averaged across N rates total plant mass was 2.26 and 11.36 g per plant at V4 and R4, respectively. Shoot mass, average across N rates was 1.77 and 9.65 g per plant at V4 and R4, respectively, and root mass, average across N rates was 0.49 and 1.71 g per plant at V4 and R4, respectively. Sulfur did not have an effect on nodules per plant but increased the percent medium size nodules at the R4 observation. There was no N by S interaction observed for nodule number, size of the nodules, and plant, root and shoot mass. As cultivars differed in their nodulation response to N and S, additional research would be helpful to screen other cultivars.展开更多
基金supported by the grant from the Natural Science Foundation of China(No.31900214 to JY)the Open Fund of State Key Laboratory of Tea Plant Biology and Utilization(SKLTOF20210113 to LL).
文摘Rhizobia induces nitrogen-fixing nodules in legumes used in agricultural production,providing a direct source of combined nitrogen to leguminous crops.Small peptides,such as CLAVATA3/EMBRYO SURROUNDING REGION peptides(CLE),are known to regulate the formation and development of nitrogen-fixing nodules in legumes.Root meristem growth factor(RGF)peptides from Medicago truncatula not only regulate root develop-ment but also modulate nodulation symbiosis with Sinorhizobium meliloti.However,the impact of RGF peptides from one leguminous species on the others remains unclear.In this study,we investigate the effects of the RGF family peptide MtRGF6p from M.truncatula on nodulation symbiosis and root development in Lotus japonicus.The MtRGF6 gene is predominantly expressed in the root nodules of M.truncatula and shows low identity with RGF homologous genes from L.japonicus.The gene promoter is active in the primordia of root nodules and lat-eral roots,as well as in young nodules and roots,and the meristem,infection,and nitrogen-fixing regions of the mature nodule.Chemically synthesized MtRGF6p promoted primary root growth in M.truncatula but sup-pressed the growth of L.japonicus primary roots.The peptide negatively affected the initiation of nodule primor-dia,the formation of infection threads,and nodulation in both legumes,with a low dosage showing effects on L.japonicus compared to M.truncatula.These results suggest that the MtRGF6 peptide from M.truncatula may serve as an inter-species signal affecting the root organ development of L.japonicus.
基金supported by the Guangdong Sci-Tech Planning Project (No. 2005B33302012,2008B020300011)
文摘Sesbania rostrata is wellknown for its stem nodulation, but the roles of stem nodulation in root nodulation and adaptation of S. rostrata to Pb/Zn-enriched tailings environment has been poorly understood. We investigated the effects of inoculating （with stem nodule treatment） and non-inoculating （without stem nodule treatment） Azorhizobium caulinodans on the growth, root nodulation, and N fixation of S. rostrata grown on three different types of soil substrata： Pb/Zn tailings, garden soil amended tailings, and garden soil. The results showed that plant height, stem basal diameter, biomass, chlorophyll content, nitrogen content and N-accumulation per plant were 2.3%-4.9%, 2.2%-7.7%, 27.8%-72.2%, 17.1%-23.5%, 12.3%-34.2%, and 43.1%-131.2%, respectively, higher in treatments with stem nodule than those without stem nodule for the same soil substrate. With respect to soil substrata, all measurements had consistently higher values in tailings than in amended tailings and garden soil, indicating that the poorer the soil condition, the greater the contribution of stem nodule. In contrast, the number and fresh weight of root nodules on plants without stem nodule were 6.9-11.6 times and 5.8-29.0 times higher than those with stem nodule, respectively, especially with respect to the plants grew on Pb/Zn tailings. In general, stem nodulation favored plant growth and nitrogen fixation of S. rostrata, but suppressed root nodulation. With the ability of stem and root nodulation, S. rostrata can be used as a pioneer plant species for remediation of Pb/Zn tailings.
基金supported by the National Natural Science Foundation of China (31271636)the earmarked fund for China Agriculture Research System (CARS-04)
文摘As an important food crop and oil crop, soybean(Glycine max [L.] Merr.) is capable of nitrogen-fixing by root nodule. Previous studies showed that GmNMH7, a transcription factor of MADS-box family, is associated with nodule development, but its specific function remained unknown. In this study, we found that GmN MH7 was specifically expressed in root and nodule and the expression pattern of GmNMH7 was similar to several genes involved in early development of nodule(GmENOD40-1, GmENOD40-2, GmNFR1 a, GmNFR5 a, and GmNIN) after rhizobia inoculation. The earlier expression peak of GmNMH7 compared to the other genes(GmENOD40-1, GmENOD40-2, GmNFR1 a, GmNFR5 a, and GmNIN) indicated that the gene is related to the nod factor(NF) signaling pathway and functions at the early development of nodule. Over-expression of GmNMH7 in hairy roots significantly reduced the nodule number and the root length. In the transgenic hairy roots, overexpression of GmN MH7 significantly down-regulated the expression levels of GmE NOD40-1, GmE NOD40-2, and GmN FR5α. Moreover, the expression of GmNMH7 could respond to abscisic acid(ABA) and gibberellin(GA_3) treatment in the root of Zigongdongdou seedlings. Over-expressing GmNMH7 gene reduced the content of ABA, and increased the content of GA_3 in the positive transgenic hairy roots. Therefore, we concluded that GmNMH7 might participate in the NF signaling pathway and negatively regulate nodulation probably through regulating the content of GA_3.
基金supported by the National 863 Program of China (2010AA10A203)the Basic Scientific and Business Fund and Central Public Research Project, China (202-10)the Special Fund for Establishment of Modern Agri-cultural R&D System, Ministry of Agriculture, China(nycytx-004)
文摘The symbiotic matching for nodulation of Bradyrhizobium japonicum strains is a synergy of multi-proteins and plays a key role in symbiotic nitrogen fixation in nature. Studies on mechanism of symbiotic matching are significant in both theory and practice. In this paper, B. japonicum USDA110-A with high symbiotic matching with high-oil content soybean cultivar Suinong 20 and B. japonicum 2178 with low symbiotic matching were selected for proteomic to reveal mechanism of different symbiotic nodulation. The results showed that the amount and categories of proteins identified in this test were different when the two strains were treated by symbiotic nodulation. There were 10 up-regulated proteins and 5 down-regulated proteins with significant difference for B. japonicum USDA110-A. Proteins associated with nodulation and metabolism of energy and material, which were propitious to symbiotic nodulation, were all up-regulated, such as PHDPS synthase, metal-dependent phosphohydrolase, glycosyl transferase family. In contrast, only 5 up-regulated and 7 down-regulated differential proteins were detected in B. japonicum 2178. Molecular chaperones and defensive proteins, which influence the folding of nascent polypeptide chains and the active of azotase were down-regulated. To a certain extent, the different responses of B. japonicum to daidzein were one of the most important reasons that cause varieties in symbiotic matching ability.
基金supported by the National High-Tech R&D Program of China (2010AA10A203)the Basic Scientific Research Special Fund of Public Research Institutions of Central Government, China (2010-12 and 2010-34)the Special Fund for Establishment of Modern Agricultural R&D System, Ministry of Finance and Ministry of Agriculture, China (nycytx-004)
文摘Competitiveness for nodulation of Bradyrhizobium japonicum strains plays a key role in symbiotic nitrogen fixation. In order to reveal the difference in competitiveness, B. japonicum 4534 with high competitiveness and B. japonicum 4222 with low competitiveness for nodulation were analyzed by proteomic technique. The results showed that differential proteins were fewer when two strains were treated with just daidzein. Only 24 and 10 differential proteins were detected with an up-regulated rate of 58 and 40% in B. japonicum 4534 and B. japonicum 4222, respectively. However, more differential proteins were detected upon treatment with daidzein and mutual extracellular materials simultaneously. There were 78 differential proteins detected in B. japonicum 4534 with 43 being up-regulated and 35 being down-regulated. These differential proteins, such as metabolism-related proteins, transporters, transcription-related proteins, translation-related proteins, and flagellin, were found to be associated with nodulation process. 25 up-regulated and 22 down-regulated proteins were detected in B. japonicum 4222. Some of these proteins were not related to nodulation. More differential proteins associated with nodulation in B. japonicum 4534 may be the reason for its high competitiveness. The results can provide a guide to the selection and inoculation of effective strains and are significant to biological nitrogen fixation.
文摘Triple Super Phosphate, TSP fertilizer, was applied @ 80 kg·ha^-1 as the source of phosphorous on six months old polybag seed- lings of Albizia chinensis, Albizia saman and Pongamia pinnta in nursery beds in Bangladesh. The effects of P-fertilizer on seedling growth and nodulation were comparcd to that of seedlings grown in unfertilized soil or in control at different harvesting intervals. The study revealed that, seedling growth was enhanced significantly with the application of P-fertilizer. The growth was found more pronounced in cases of A. saman and P. pinnata, whereas it was not noticeable and showed depressed growth in case of A. chinensis. The study also suggests that nodulation in terms of nodule number and size was also increased significantly with P-fertilization except in case ofP. pinnata, where higher harvesting intervals lowered the nodulation performance of that species
文摘A study was conducted to test the influence of different inorganic fertilizers （phosphorous and potassium） on the nodulation and growth of Dalbergia sissoo grown in the nursery. Before seeds sowing, different combinations of P, K fertilizers were incorporated with the nutrient-deficient natural forest soils, and then amended with cowdung （soil： cowdung = 3：1）. Nodulation status （nodule number, shape, fresh weight, dry weight and color） in the roots and the plant growth parameters （length of shoot and root, collar diameter, fresh and dry weight of shoot and root） were recorded 60 days after seeds sowing. Nodulation status and growth of the plants varied significantly （P〈0.05） in the soils amended with fertilizers in comparison to the control. The highest nodule number （62）, fresh （0.50 g） and dry （0.07 g） weights were recorded with the dose of PK at the rate of 160 kg/hm2. Nodule shape and color also varied widely in different treatments. In case of plant growth parameters, shoot and root length, collar diameter, fresh and dry weight of the plants took on a significant difference （P〈0.05） among various combination of fertilizers. From the study, it is revealed that PK at the rate of 160 kg/hm^2 fertilizer with soil and cowdung mixture （soil： eowdung = 3：1） is recommended for optimum growth and nodule formation of D. sissoo in degraded soils at a nursery level.
文摘Bradyrhizobia are known symbiotic partners of soybean. However, some soybean cultivars restrict nodulation by some Bradyrhizobium bacterial strains. These restrictions are related to compatibility between the Rj genes of soybean cultivars and nodulation types of inoculated bacteria. The objective of this study was to determine nodulation incompatibility of Type B strains with Rj3 soybean cultivars. Newly isolated B. elkanii strains BLY3-8 and BLY6-1 from Myanmar and specific strain Bradyrhizobium elkanii USDA33, which are incompatible with Rj3 soybean cultivars, and B. japonicum USDA110 were used as inoculants to check compatibility or incompatibility with Rj3 soybean cultivars. Nitrogen fixation activity was measured by the acetylene reduction method. Ethylene concentration (reduction of acetylene) was determined by flame ionization gas chromatography. According to the inoculation test results, USDA110 was compatible with all soybean cultivars because it formed effective nodules (Figure S1 in Appendix) and possessed nitrogenase activity. Similarly, B. elkanii strains BLY3-8, BLY6-1, and USDA33 were highly compatible with non-Rj and Rj4-gene harboring soybean cultivars because they had the ability to form functional nodules and possessed nitrogenase activity. Inversely, BLY3-8, BLY6-1, and USDA33 were incompatible with Rj3 soybean cultivars because they produced ineffective nodules. Consequently, the ratio of ineffective nodule number to total nodule number was >0.5. Therefore, nodule formation by the newly isolated B. elkanii strains BLY3-8 and BLY6-1 was restricted by the Rj3 soybean cultivars potentially making them useful as specific strains to detect the Rj3 gene in soybean cultivars.
文摘Groundnut (Arachis hypogaea), cowpea (Vigna unguiculata) and soybean (Vigna radiata) are the main food legumes grown in Cote d’Ivoire and the localities of Haut-Sassandra. These legumes are highly valued for their nutritional, agronomic and economic value. Groundnut, cowpea and soybean are the main food legumes grown in Cote d’Ivoire and in the localities of Haut-Sassandra. On the other hand, Ivorian soils are characterized by a tendency towards acidification and a decrease in the content of nutrients such as phosphorus and nitrogen which have a direct impact on the products. To restore soil fertility, farmers use mineral fertilization. However, this fertilization has an influence on the nodulation of these legumes. The study took place at Jean Lorougnon University. We adopted a completely random experimental block device. The parameters measured included the number of nodules, the length and weight of the plant, the length and weight of the root system. Our results showed that mineral fertilization reduced the nodulation capacity of legumes. However, a small dose of phosphorus ( g) would be required for early growing legumes.
文摘Vigna unguiculata(L.) Walp (cowpea) is a tropical legume of very high nutritive and economic values. A laboratory experiment was conducted to evaluate the BNF (biological nitrogen fixation) efficiency of 4 strains of Bradyrhizobium sp. (VUXYI, VUIEI, VUMDSI and VUIDI). From the results obtained these strains were classified into efficiency groups, with VUIDI being the most efficient and VUXYI the least efficient.The effect of inoculation was tested on 2 cowpea varieties in a field experiment. Remarkable increases in nodulation biomass and crop yield were observed. An increase from 58% to 81% in dry seed was obtained for the two varieties. A significance test revealed a significantly positive correlation between nodulation and biomass.
文摘An experiment was conducted to assess the effect of Phosphorous （P） fertilizer （i.e. TSP or triple super phosphate @ 80 kg/hm^2） on seedling growth and nodulation capabilities of three potentially important agroforestry tree species （Acacia auriculiformis, Albizia lebbeck and Albizia procera） of Bangladesh. The study was conducted in nursery beds with six-month-old polybag seedlings ofA. auriculiformis, A. lebbeck and A. procera. The effects of P fertilizer on seedling growth and nodulation were compared with that of the seedlings grown in control （i.e. unfertilized soil）. The observations revealed that the seedling growth was enhanced significantly with the application of P fertilizer. The growth was found more pronounced in A. auriculiformis, whereas it was not apparent and shows depressed growth in case ofA. lebbeck. The study also suggests that the nodulation in terms of nodule number and size was also increased significantly with the application of P fertilizer.
文摘Effects of inoculation of Rhizobium suspension on nodulation and plant growth were examined withAlbizzia procera, Albizzia lebbeck and Leucaena leucocephala seedlings grown on sterilized and non-sterilizedsoil media. Inoculation resulted in nodule number increases of 28.6, 29.02 and 23.9 times in sterilized soiland 3.4, 3.6 and 3.27 times in non-sterilized soil for A. parocera A. lebbeck and L. leucocephala seedlingsrespectively. Total dry mass increased by 127.6%, 66.7% and 60.7% in sterilized soil and 100%, 95.5%and 52.65% in non-sterilized soil for these three legume trees, respectively, after a period of two months.Significalltly high inoculation responses of root length, root diameter, collar diameter, shoot length, and drymass of root, shoot, leaves and nodules were also observed in both sterilized and non-sterilized soil media ascompared to respective control treatments. The response to inoculation was strong in sterilized and modestin non-sterilized soils. The significantly higher response to Rhizobium inoculation over control in all thespecies tested suggested that application of Rhizobium greatly enhanced plant growth, nodulation, biomassproduction and nitrogen-fixing activity of the nodules.
基金supported by the National Natural Science Foundation of China(31271636)the China Agriculture Research System(CARS-04)。
文摘Soybean(Glycine max[L.]Merr.)is a food and oil crop whose growth and yield are influenced by root and nodule development.In the present study,Gm NMHC5 was found to promote the formation of nodules in overexpressing mutants.In contrast,the number of nodules in Gmnmhc5 edited with CRISPR/Cas9 decreased sharply.In 35 S:Gm NMHC5 mutants,expression levels of genes involved in nodulation were significantly up-regulated.Both in vitro and in vivo biochemical analyses showed that Gm NMHC5 directly interacted with Gm GAI(a DELLA protein),and the content of gibberellin 3(GA_(3))in overexpressing mutants was lower than that in the wild type.These results revealed that Gm NMHC5 participates in the classical GA signaling pathway,and may regulate the content of GA_3 to match the optimal concentration required for nodule formation,thereby promoting nodulation by directly interacting with Gm GAI.A model illustrating the mechanism by which Gm NMHC5 promotes soybean nodulation is presented.
基金supported by the National Key Research and Development Program of China (2018YFD10009000)。
文摘Nitrogen(N) is an essential macronutrient for plant growth and productivity. Leguminous plants establish symbiotic relationships with nitrogen-fixing rhizobial bacteria to use atmospheric dinitrogen gas to meet high N demand under low-N conditions. Nodule formation and N fixation are energy-consuming processes and are inhibited by nitrate present in the environment. Previous studies in model leguminous plants characterized NIN-LIKE PROTEIN(NLP) proteins that mediate nitrate control of root nodule symbiosis, but the mechanism by which nitrate regulates soybean root nodules via NLP remains unclear. In the soybean genome we found four homologs of AtNLP7, named GmNLP7a–GmNLP7d. We showed that the expression of GmNLP7s is responsive to nitrate but not to rhizobial infection and localized GmNLP7a to the nucleus. Downregulation of GmNLP7s increased nodule number, and overexpression of GmNLP7a(GmNLP7aOE) reduced nodule number regardless of nitrate availability, suggesting a negative role for GmNLP7s in nodulation. Nitrogenase activity in the GmNLP7aOE line was comparable to that of the wild type, indicating that GmNLP7a does not affect mature nodule activity. Overexpression of GmNLP7a downregulated the expression of GmNIN1a and GmENOD40-1. GmNLP7a interacted with GmNIN1a via the PB1domain. Our results reveal a new regulator of GmNLP7 in nodulation and a molecular mechanism by which nitrate affects nodule number in soybean.
文摘The study was carried out on the impact assessment of the form and nature of the different nitrogen sources used in culture on growth and nodulation of pigeon pea (Cajanus cajan (L.) Millsp) during 3 months of observation on sandy soil of Mount Amba (at the University of Kinshasa in the Democratic Republic of Congo). Height and collar diameter growth, underground and total biomass dry weight, number and dry pea nodules and nodulation index have been evaluated at 4, 6, 8, 10 and 12 weeks of growth to assess the response of the legume to mineral nitrogen and organic nitrogen from chickens manure and pig feces. After observations, it appears that all the treatments soil showed different effects on growth and nodulation of pigeon pea. Therefore, only the soil received 1 kg of pig feces stimulated (p ≤ 0.05) the development of pigeon pea which resulted in good growth (nodulation 116.8 nodules and nodulation index of 5.0) and biomass production (25.3 gr per plant) while the addition of chicken manure, whatever the dose, reduced them.
文摘A total of 110 strains of nodule bacteria was isolated from plants Onobrychis transcaucasica and Onobrychis chorassanica. Nodulation study of bacteria in both Onobrychis plant species in microvegetation experiment gave a very low nodulation on plant roots. The intensive nodulation of Onobrychis plants was recorded in vegetation experiment and for Onobrychis transcaucasica the efficiently-nodulating strains were found OT102, OT103, OT117, OT121, OT130, OT136, ОT139, ОT140, while for Onobrychis chorassanica plants—ОC106, ОC107, ОC109, ОC112, ОT103, ОT117 and ОT123 strains. Nucleotide sequencing of the 16S rRNA gene and BLAST analysis showed that nodule bacteria of Onobrychis plants were related to Rhizobium, Burkholderia, Enterobacter and Pantoea genera. It has been shown a possibility of growing up of Onobrychis plants at minimal additional moisture of sabulous soils in the Kyzyl Kum Desert, creating artificial pastures and thereby immobilizing the desert blown sands.
文摘Soybean (Glycine max L.) plays an essential role in human nutrition as a protein source, and in plant nutrition as a N source. The rate of N fixation varies depending on the cultivars and compatibility between the inoculated Rhizobium strain and the host cultivar. Characterizing the nodulation regulatory (Rj) genes is necessary to determine the compatibility of cultivars and Rhizobium strains. Rj genes were previously identified based on inoculation tests and PCR analyses. The six cultivars Yezin-3, Yezin-7, Yezin-11, Shan Seine (Local), Madaya (Local), and Hinthada (Local) were identified as harboring the Rj4 gene. Two cultivars, Yezin-6 and Yezin-8, were classified as non-Rj-gene harboring. Two other cultivars, Yezin-9 and Yezin-10, were identified as Rj3- and Rj2Rj3-gene harboring, respectively. Ours is the first report on Rj3- and Rj2Rj3-gene harboring cultivars in Myanmar. We evaluated Myanmar soybean cultivars for symbiotic effectiveness, relying on the standard strain Bradyrhizobium japonicum USDA110. In our first experiment, the soybean cultivar Yezin-11 (Rj4) showed the highest N fixing potential. Based on their potential for fixing N and nodulation, the top six soybean cultivars were Yezin-11 (Rj4), Yezin-9 (Rj3), Yezin-6 (non-Rj), Yezin-8 (non-Rj), Yezin-3 (Rj4) and Yezin-10 (Rj2Rj3). These cultivars were selected for a second experiment, which revealed that the N fixation, nodulation, and plant growth of Yezin-11 (Rj4) *Corresponding author. A. Z. Htwe et al. 2800 were superior to the other cultivars. We conclude that Yezin-11 (Rj4) is the most efficient cultivar for nodulation and N fixation when inoculated with B. japonicum USDA110.
文摘The purpose of this research was to evaluate the nodulation potential of 31 Argentinean soybean commercial cultivars. Those with the highest nodulation capacity response developed twice the amount of nodules than the low nodulating ones, which is the variation contained in soybean genotypes. Furthermore, this was not due to bacterial promiscuity, since the response was independent of the bradyrhizobia strain inoculated. The ability of cultivars to develop a larger number and biomass of nodules was unrelated with the maturity group they belong to and also was not a response to quorum sensing effects. Our results suggest that breeding programs can be aimed at improving the nodulation capacity of soybean and that cultivars from different maturity groups can be a source of nodulation QTLs.
文摘Legumes, in symbiotic association with Rhizobia, are able to fix atmospheric N. Six local lima bean (Phaseolus lunatus) cultivars were grown under rainfed conditions in a coastal savannah environment. Objectives of the study were to evaluate the nodulation and fixed atmospheric N levels of the six local lima bean cultivars using both the 15N isotope dilution method and N difference method (NDM). The linear relationship between fixed atmospheric N estimated using the 15N isotope dilution method and NDM, was also assessed. The experiment was arranged in a randomized complete block design (RCBD) in three replicates with seven treatments, comprising six lima bean cultivars (B1, B2, B3, B4, B5 and B6) and the early maturing local maize variety, “Doke”, as the reference crop. Total, effective nodules (EN) and non-effective nodules (NEN) were determined on 42 and 56 days after planting (DAP). The 15N isotopic dilution method and NDM were used to quantify the fixed atmospheric N by the lima bean cultivars on 60 DAP. Effective root nodules per plant (EN) on 56 DAP ranged from 0.71 to 1.22, with the lima bean cultivar B4 having the highest value and cultivars B2 and B5 having the lowest value of EN, respectively. Similarly on 56 DAP, the lima bean cultivar B4 had the highest NEN value while cultivars B1, B2 and B5 had the lowest NEN value of 0.71 per plant. The mean fixed atmospheric N was 8.98 kg·ha-1, based on the 15N isotope dilution method, which was lower than 10.13 kg·ha-1 of fixed atmospheric N determined using NDM. The linear relationship between fixed atmospheric N estimated using the 15N isotope dilution method and that estimated using the NDM, was positive but of average quality as the R2 value was 0.56. Consequently, the linear model obtained from this relationship is moderate as 56% of the data used for the linear regression analysis were accounted for by the linear regression model developed. However, NDM could be used for fast screening to select lima bean cultivars for a more detailed study to identify cultivars with promising fixed atmospheric N capabilities. Generally, results of the study provide opportunities for designing breeding and other agronomic programmes for enhancing the productivity and N-fixing capacity of local lima beans in the coastal savannah environment.
文摘Soybean [<em>Glycine max</em> (L.) Merrill] seed yields in the northern United States may increase with the application of fertilizers;however Nitrogen (N) may decrease root nodulation. This study was conducted to understand the impact of N and sulfur (S) fertilization on soybean nodulation, plant, shoot and root biomass. Two cultivars were planted in experiments across ten site-years during 2015-2016. Plant observations took place at the V4 and R4 soybean growth stages. There were 41% more nodules per plant at R4 compared to V4 (38.3 vs 27.2 nodules, respectively). Cultivars responded differently to N and S fertilizer. The nodules per plant between the cultivars (30.3 vs 24.4) were different as well as the percent medium and large-sized nodules, which indicates the need to evaluate additional genotypes. Adding N decreased root nodulation (from 31.8 to 23.7 nodules per plant) and decreased nodule size but had no effect on plant, shoot or root mass. Averaged across N rates total plant mass was 2.26 and 11.36 g per plant at V4 and R4, respectively. Shoot mass, average across N rates was 1.77 and 9.65 g per plant at V4 and R4, respectively, and root mass, average across N rates was 0.49 and 1.71 g per plant at V4 and R4, respectively. Sulfur did not have an effect on nodules per plant but increased the percent medium size nodules at the R4 observation. There was no N by S interaction observed for nodule number, size of the nodules, and plant, root and shoot mass. As cultivars differed in their nodulation response to N and S, additional research would be helpful to screen other cultivars.
