Technical Challenges in Evaluating Southern China’s Forage Germplasm Resources

The present status of the collection, conservation and utilisation of the pasture germplasm in tropical and subtropical zones in China is reviewed. The Tropical Pasture Research Centre (TPRC) of Chinese Academy of Tropical Agricultural Sciences (CATAS) has been engaged in this research since the 1940s. A low temperature gene bank, an in vitro plant library and a nursery station have been established. In total, 5890 indigenous fodder materials belonging to 478 species, 161 genera and 12 families have been surveyed and collected in South China; 1130 exotic materials belonging to 87 species, 42 genera of grasses and legumes have been introduced and conserved; 3769 materials from 301 species, 127 genera, 12 families have been conserved in the seed bank; 482 materials belonging to 6 species, 6 genera, 3 families have been propagated in vitro, and 388 materials belonging to 10 species, 8 genera, 3 families grown in the plant preservation nursery. Suggestions are made for developing and utilising southern Chinese grassland resources

Mining and utilization of salinity tolerant legumes in tropical coastal agroecosystems: An overview

Coastal saline soils are increasing year by year caused by climate change and human activities. Most of the coastal saline soils are idle due to their high salinity level and few crops can grow normally. Salinity tolerant legumes are naturally tolerant to salt, which can ecologically cover the coastal saline soil, enhance soil fertility by symbiotic nitrogen fixation and increase the smallholder farmers’ benefits in terms of forage, green manure, food or medicine. However, few reports are available for the systematic evaluation of salinity tolerant legumes. This review summarizes and evaluates currently available salinity tolerant legume species that could potentially be used and discusses their potential for integration into smallholder mixed coastal systems of the Asia-Pacific region. Fourty four salinity tolerant legumes were summarized, six of them showed a high level of salinity tolerance, 17 of them showed a moderate level of salinity tolerance and 21 of them showed potential salinity tolerance but need to be further studied. Many gaps such as combined tolerance evaluation, nitrogen fixation efficiency, animal feeding experiments and salinity tolerant rhizobia screening/inoculants exist. Case studies demonstrate legumes could be used to reclaim coastal saline soils, but commitment and support from government and public services are necessary to address both seed system and extension needs, through the provision of adequate incentives, policies and development efforts

Technical challenges in evaluating southern China’s forage germplasm resources

The present status of the collection, preservation and utilization of pasture germplasm in tropical and subtropical zones in China is reviewed. The Tropical Pasture Research Centre (TPRC) of the Chinese Academy of Tropical Agricultural Sciences (CATAS) has been engaged in this research since the 1940s. A low-temperature gene bank, an in-vitro plant library and a nursery station have been established. In total, 5890 indigenous fodder accessions belonging to 478 species, 161 genera and 12 families have been surveyed and collected in South China; 1130 exotic accessions belonging to 87 species and 42 genera of grasses and legumes have been introduced and are preserved. In the seed bank, 3769 accessions from 301 species, 127 genera and 12 families are maintained; in the form of in-vitro culture, 482 accessions belonging to 6 species, 6 genera and 3 families are preserved; and in the plant preservation nursery 388 accessions belonging to 10 species, 8 genera and 3 families. A list of 12 forage legume and 9 grass cultivars released by CATAS during 1991-2011 is presented and suggestions are made for developing and utilizing southern Chinese grassland germplasm resources.</p

Ohr and OhrR Are Critical for Organic Peroxide Resistance and Symbiosis in Azorhizobium caulinodans ORS571

Azorhizobium caulinodans is a symbiotic nitrogen-fixing bacterium that forms both root and stem nodules on Sesbania rostrata. During nodule formation, bacteria have to withstand organic peroxides that are produced by plant. Previous studies have elaborated on resistance to these oxygen radicals in several bacteria; however, to the best of our knowledge, none have investigated this process in A. caulinodans. In this study, we identified and characterised the organic hydroperoxide resistance gene ohr (AZC_2977) and its regulator ohrR (AZC_3555) in A. caulinodans ORS571. Hypersensitivity to organic hydroperoxide was observed in an ohr mutant. While using a lacZ-based reporter system, we revealed that OhrR repressed the expression of ohr. Moreover, electrophoretic mobility shift assays demonstrated that OhrR regulated ohr by direct binding to its promoter region. We showed that this binding was prevented by OhrR oxidation under aerobic conditions, which promoted OhrR dimerization and the activation of ohr. Furthermore, we showed that one of the two conserved cysteine residues in OhrR, Cys11, was critical for the sensitivity to organic hydroperoxides. Plant assays revealed that the inactivation of Ohr decreased the number of stem nodules and nitrogenase activity. Our data demonstrated that Ohr and OhrR are required for protecting A. caulinodans from organic hydroperoxide stress and play an important role in the interaction of the bacterium with plants. The results that were obtained in our study suggested that a thiol-based switch in A. caulinodans might sense host organic peroxide signals and enhance symbiosis

Table_6_Physio-biochemical and transcriptomic analysis of Bacillus amyloliquefaciens PG-4-induced salt stress tolerance in Macrotyloma uniflorum.DOCX

IntroductionMacrotyloma uniflorum is an important legume fodder crop and green fertilizer. Salinity impedes plant growth and productivity of legume crops by disrupting the ionic and osmotic balance and hormonal regulation. Plant growth-promoting rhizobacteria (PGPR) are rhizosphere bacteria that contribute to the improvement of plant growth through diverse physiological mechanisms.MethodsIn this study, the growth promoting characteristics of the isolated strain Bacillus amyloliquefaciens PG-4 were analyzed, and to further investigated the possible mechanism of PG-4 in mitigating the damage caused by salt stress in M. uniflorum plants through pot experiments.ResultsIn presence of different salt levels, PG-4 showed a high potentiality to produce several plant growth promoting metabolites such as NH3, siderophore, 1-aminocyclopropane-1-carboxylic acid deaminase (ACC-deaminase), and hydrolytic enzymes. Inoculation of the PG-4 significantly enhanced plant tolerance to salt stress, as demonstrated by promotion of plant growth (shoot and root biomass) under salt stress condition. Furthermore, PG-4 improved salt tolerance of Macrotyloma uniflorum seedlings by affecting the antioxidant enzymes including peroxidase (POD) and superoxide dismutase (SOD), by increasing the levels of proline, soluble sugars and chlorophyll. Treatment with PG-4 increased the K+ content while decreased the Na+ concentration level under salt stress. Transcriptomic analysis revealed 5525 genes were differentially expressed (PG-4-inoculated versus non-inoculated samples) at 0 mM NaCl, of which 3277 were upregulated and 2248 downregulated, while 1298 genes were differentially expressed at 100 mM NaCl, of which 819 were upregulated and 479 were downregulated. GO and KEGG enrichment analyses showed that these DEGs were significantly enriched in several terms and pathways mainly involved in the regulation of the cellular redox state, cell wall modification, metabolic adjustments, hemoglobin, biosynthesis of secondary metabolites and plant hormone signal transduction.DiscussionThese data showed that Bacillus amyloliquefaciens PG-4 significantly enhance salt stress tolerance in Macrotyloma uniflorum plants during salt stress conditions. Therefore, the results may be useful for explaining the mechanism by which PGPR inoculation regulates the salt tolerance of crops.</p

Image_1_Physio-biochemical and transcriptomic analysis of Bacillus amyloliquefaciens PG-4-induced salt stress tolerance in Macrotyloma uniflorum.JPEG

IntroductionMacrotyloma uniflorum is an important legume fodder crop and green fertilizer. Salinity impedes plant growth and productivity of legume crops by disrupting the ionic and osmotic balance and hormonal regulation. Plant growth-promoting rhizobacteria (PGPR) are rhizosphere bacteria that contribute to the improvement of plant growth through diverse physiological mechanisms.MethodsIn this study, the growth promoting characteristics of the isolated strain Bacillus amyloliquefaciens PG-4 were analyzed, and to further investigated the possible mechanism of PG-4 in mitigating the damage caused by salt stress in M. uniflorum plants through pot experiments.ResultsIn presence of different salt levels, PG-4 showed a high potentiality to produce several plant growth promoting metabolites such as NH3, siderophore, 1-aminocyclopropane-1-carboxylic acid deaminase (ACC-deaminase), and hydrolytic enzymes. Inoculation of the PG-4 significantly enhanced plant tolerance to salt stress, as demonstrated by promotion of plant growth (shoot and root biomass) under salt stress condition. Furthermore, PG-4 improved salt tolerance of Macrotyloma uniflorum seedlings by affecting the antioxidant enzymes including peroxidase (POD) and superoxide dismutase (SOD), by increasing the levels of proline, soluble sugars and chlorophyll. Treatment with PG-4 increased the K+ content while decreased the Na+ concentration level under salt stress. Transcriptomic analysis revealed 5525 genes were differentially expressed (PG-4-inoculated versus non-inoculated samples) at 0 mM NaCl, of which 3277 were upregulated and 2248 downregulated, while 1298 genes were differentially expressed at 100 mM NaCl, of which 819 were upregulated and 479 were downregulated. GO and KEGG enrichment analyses showed that these DEGs were significantly enriched in several terms and pathways mainly involved in the regulation of the cellular redox state, cell wall modification, metabolic adjustments, hemoglobin, biosynthesis of secondary metabolites and plant hormone signal transduction.DiscussionThese data showed that Bacillus amyloliquefaciens PG-4 significantly enhance salt stress tolerance in Macrotyloma uniflorum plants during salt stress conditions. Therefore, the results may be useful for explaining the mechanism by which PGPR inoculation regulates the salt tolerance of crops.</p

Table_10_Physio-biochemical and transcriptomic analysis of Bacillus amyloliquefaciens PG-4-induced salt stress tolerance in Macrotyloma uniflorum.DOCX

IntroductionMacrotyloma uniflorum is an important legume fodder crop and green fertilizer. Salinity impedes plant growth and productivity of legume crops by disrupting the ionic and osmotic balance and hormonal regulation. Plant growth-promoting rhizobacteria (PGPR) are rhizosphere bacteria that contribute to the improvement of plant growth through diverse physiological mechanisms.MethodsIn this study, the growth promoting characteristics of the isolated strain Bacillus amyloliquefaciens PG-4 were analyzed, and to further investigated the possible mechanism of PG-4 in mitigating the damage caused by salt stress in M. uniflorum plants through pot experiments.ResultsIn presence of different salt levels, PG-4 showed a high potentiality to produce several plant growth promoting metabolites such as NH3, siderophore, 1-aminocyclopropane-1-carboxylic acid deaminase (ACC-deaminase), and hydrolytic enzymes. Inoculation of the PG-4 significantly enhanced plant tolerance to salt stress, as demonstrated by promotion of plant growth (shoot and root biomass) under salt stress condition. Furthermore, PG-4 improved salt tolerance of Macrotyloma uniflorum seedlings by affecting the antioxidant enzymes including peroxidase (POD) and superoxide dismutase (SOD), by increasing the levels of proline, soluble sugars and chlorophyll. Treatment with PG-4 increased the K+ content while decreased the Na+ concentration level under salt stress. Transcriptomic analysis revealed 5525 genes were differentially expressed (PG-4-inoculated versus non-inoculated samples) at 0 mM NaCl, of which 3277 were upregulated and 2248 downregulated, while 1298 genes were differentially expressed at 100 mM NaCl, of which 819 were upregulated and 479 were downregulated. GO and KEGG enrichment analyses showed that these DEGs were significantly enriched in several terms and pathways mainly involved in the regulation of the cellular redox state, cell wall modification, metabolic adjustments, hemoglobin, biosynthesis of secondary metabolites and plant hormone signal transduction.DiscussionThese data showed that Bacillus amyloliquefaciens PG-4 significantly enhance salt stress tolerance in Macrotyloma uniflorum plants during salt stress conditions. Therefore, the results may be useful for explaining the mechanism by which PGPR inoculation regulates the salt tolerance of crops.</p

Image_5_Physio-biochemical and transcriptomic analysis of Bacillus amyloliquefaciens PG-4-induced salt stress tolerance in Macrotyloma uniflorum.JPEG

IntroductionMacrotyloma uniflorum is an important legume fodder crop and green fertilizer. Salinity impedes plant growth and productivity of legume crops by disrupting the ionic and osmotic balance and hormonal regulation. Plant growth-promoting rhizobacteria (PGPR) are rhizosphere bacteria that contribute to the improvement of plant growth through diverse physiological mechanisms.MethodsIn this study, the growth promoting characteristics of the isolated strain Bacillus amyloliquefaciens PG-4 were analyzed, and to further investigated the possible mechanism of PG-4 in mitigating the damage caused by salt stress in M. uniflorum plants through pot experiments.ResultsIn presence of different salt levels, PG-4 showed a high potentiality to produce several plant growth promoting metabolites such as NH3, siderophore, 1-aminocyclopropane-1-carboxylic acid deaminase (ACC-deaminase), and hydrolytic enzymes. Inoculation of the PG-4 significantly enhanced plant tolerance to salt stress, as demonstrated by promotion of plant growth (shoot and root biomass) under salt stress condition. Furthermore, PG-4 improved salt tolerance of Macrotyloma uniflorum seedlings by affecting the antioxidant enzymes including peroxidase (POD) and superoxide dismutase (SOD), by increasing the levels of proline, soluble sugars and chlorophyll. Treatment with PG-4 increased the K+ content while decreased the Na+ concentration level under salt stress. Transcriptomic analysis revealed 5525 genes were differentially expressed (PG-4-inoculated versus non-inoculated samples) at 0 mM NaCl, of which 3277 were upregulated and 2248 downregulated, while 1298 genes were differentially expressed at 100 mM NaCl, of which 819 were upregulated and 479 were downregulated. GO and KEGG enrichment analyses showed that these DEGs were significantly enriched in several terms and pathways mainly involved in the regulation of the cellular redox state, cell wall modification, metabolic adjustments, hemoglobin, biosynthesis of secondary metabolites and plant hormone signal transduction.DiscussionThese data showed that Bacillus amyloliquefaciens PG-4 significantly enhance salt stress tolerance in Macrotyloma uniflorum plants during salt stress conditions. Therefore, the results may be useful for explaining the mechanism by which PGPR inoculation regulates the salt tolerance of crops.</p

Table_2_Physio-biochemical and transcriptomic analysis of Bacillus amyloliquefaciens PG-4-induced salt stress tolerance in Macrotyloma uniflorum.DOCX

IntroductionMacrotyloma uniflorum is an important legume fodder crop and green fertilizer. Salinity impedes plant growth and productivity of legume crops by disrupting the ionic and osmotic balance and hormonal regulation. Plant growth-promoting rhizobacteria (PGPR) are rhizosphere bacteria that contribute to the improvement of plant growth through diverse physiological mechanisms.MethodsIn this study, the growth promoting characteristics of the isolated strain Bacillus amyloliquefaciens PG-4 were analyzed, and to further investigated the possible mechanism of PG-4 in mitigating the damage caused by salt stress in M. uniflorum plants through pot experiments.ResultsIn presence of different salt levels, PG-4 showed a high potentiality to produce several plant growth promoting metabolites such as NH3, siderophore, 1-aminocyclopropane-1-carboxylic acid deaminase (ACC-deaminase), and hydrolytic enzymes. Inoculation of the PG-4 significantly enhanced plant tolerance to salt stress, as demonstrated by promotion of plant growth (shoot and root biomass) under salt stress condition. Furthermore, PG-4 improved salt tolerance of Macrotyloma uniflorum seedlings by affecting the antioxidant enzymes including peroxidase (POD) and superoxide dismutase (SOD), by increasing the levels of proline, soluble sugars and chlorophyll. Treatment with PG-4 increased the K+ content while decreased the Na+ concentration level under salt stress. Transcriptomic analysis revealed 5525 genes were differentially expressed (PG-4-inoculated versus non-inoculated samples) at 0 mM NaCl, of which 3277 were upregulated and 2248 downregulated, while 1298 genes were differentially expressed at 100 mM NaCl, of which 819 were upregulated and 479 were downregulated. GO and KEGG enrichment analyses showed that these DEGs were significantly enriched in several terms and pathways mainly involved in the regulation of the cellular redox state, cell wall modification, metabolic adjustments, hemoglobin, biosynthesis of secondary metabolites and plant hormone signal transduction.DiscussionThese data showed that Bacillus amyloliquefaciens PG-4 significantly enhance salt stress tolerance in Macrotyloma uniflorum plants during salt stress conditions. Therefore, the results may be useful for explaining the mechanism by which PGPR inoculation regulates the salt tolerance of crops.</p