Planting grass and legume mixtures on improved grasslands has the potential advantage of realizing both higher yields and lower environmental pollution by optimizing the balance between applied N fertilizer and the na...Planting grass and legume mixtures on improved grasslands has the potential advantage of realizing both higher yields and lower environmental pollution by optimizing the balance between applied N fertilizer and the natural process of legume biological nitrogen fixation. However, the optimal level of N fertilization for grass-legume mixtures, to obtain the highest yield, quality, and contribution of N2 fixation, varies with species. A greenhouse pot experiment was conducted to study the temporal dynamics of N2 fixation of alfalfa （Medicago sativa L.） grown alone and in mixture with smooth bromegrass （Bromus inermis Leyss.） in response to the addition of fertilizer N. Three levels of N （0, 75, and 150 kg ha-1） were examined using 15N-labeled urea to evaluate N2 fixation via the 15N isotope dilution method. Treatments were designated NO （0.001 g per pot）, N75 （1.07 g per pot） and N150 （2.14 g per pot）. Alfalfa grown alone did not benefit from the addition of fertilizer N; dry matter was not significantly increased. In contrast, dry weight and N content of smooth bromegrass grown alone was increased significantly by N application. When grown as a mixture, smooth bromegrass biomass was increased significantly by N application, resulted in a decrease in alfalfa biomass. In addition, individual alfalfa plant dry weight （shoots＋roots） was significantly lower in the mixture than when grown alone at all N levels. Smooth bromegrass shoot and root dry weight were significantly higher when grown with alfalfa than when grown alone, regardless of N application level. When grown alone, alfalfa＇s N2 fixation was reduced with N fertilization （R2=0.9376,P=0.0057）. When grown in a mixture with smooth bromegrass, with 75 kg ha-1 of N fertilizer, the percentage of atmospheric N2 fixation contribution to total N in alfalfa （%Ndfa） had a maximum of 84.07 and 83.05% in the 2nd and 3rd harvests, respectively. Total 3-harvest %Ndfa was higher when alfalfa was grown in a mixture than when grown alone （shoots： ｜t｜=3.39, P=0.0096; root： ｜t｜=3.57, P=0.0073）. We believe this was due to smooth bromegrass being better able to absorb available soil N （due to its fibrous root system）, resulting inlower soil N availability and allowing alfalfa to develop an effective N2 fixing symbiosis prior to the 1st harvest. Once soil N levels were depleted, alfalfa was able to fix N2, resulting in the majority of its tissue N being derived from biological nitrogen fixation （BNF） in the 2nd and 3rd harvests. When grown in a mixture, with added N, alfalfa established an effective symbiosis earlier than when grown alone; in monoculture BNF did not contribute a significant portion of plant N in the N75 and N150 treatments, whereas in the mixture, BNF contributed 17.90 and 16.28% for these treatments respectively. Alfalfa has a higher BNF efficiency when grown in a mixture, initiating BNF earlier, and having higher N2 fixation due to less inhibition by soil-available N. For the greatest N-use-efficiency and sustainable production, grass-legume mixtures are recommended for imDrovino orasslands, usino a moderate amount of N fertilizer （75 kq N ha-l） to provide optimum benefits.展开更多
A full-length cDNA of proteinase inhibitor gene with completed open reading frame of 116 amino acids was cloned from Ralstonia solanacearum （Rs） resistant potato leaves using the rapid amplification of cDNA ends （R...A full-length cDNA of proteinase inhibitor gene with completed open reading frame of 116 amino acids was cloned from Ralstonia solanacearum （Rs） resistant potato leaves using the rapid amplification of cDNA ends （RACE） method and designated as StPI. BLAST search against NCBI showed that the StPI gene shared 89% identity with potato proteinase inhibitor I precursor in nucleotide and 74% in amino acid. Analysis of semi-quantitative RT-PCR indicated that this gene was induced by Rs as well as up-regulated by jasmonic acid （JA）. The StPI gene expression reached the highest level during 6-12 h post Rs-inoculation or JA-treatment, and then leveled off. Moreover, this gene was strongly induced by JA and its mRNA accumulation increased more quickly than that of Rs-inoculation. The StPI gene may play a role in potato resistance against Rs. The induction of StPI by Rs invasion may have a similar signal transduction pathway with JA treatment.展开更多
This study is to investigate the role of lipid transfer protein （LTP1） gene of potato （Solanum tuberosum） in bacterial wilt （Ralstonia solanacearum） resistance. A novel cDNA clone encoding nsLTP was isolated fro...This study is to investigate the role of lipid transfer protein （LTP1） gene of potato （Solanum tuberosum） in bacterial wilt （Ralstonia solanacearum） resistance. A novel cDNA clone encoding nsLTP was isolated from cultivated potato （Solanum tuberosum） infected with R. solanacearum by 5＇-rapid amplification of cDNA ends （RACE）. The temporal and spatial expression of StLTPbl was studied during the early stages of potato-R, solanacearum interaction by reverse transcriptase PCR （RT-PCR） and Northern blotting. The sequence analysis of the cloned cDNA, named StLTPbl, showed 691 bp which encoded a type 1 nsLTP of 91 amino acids. Construction of a phylogenic tree showed that StLTPbl is well conserved in the coding region with high identity at the amino acid level with other Solanaceae nsLTPs. The temporal and spatial expression of StLTPbl was studied during the early stages of potato-R, solanacearum interaction. StLTPbl transcription is induced faster and transcripts accumulate to higher concentrations in resistant compared with susceptible genotypes by the pathogen. Dominant differences in the pathogen-induced gene expression pattern between the upper and lower leaves and stems were observed within the same genotypes. In situ hybridization results showed that the StLTPbl mRNA was localized in phloem cells of vascular tissues in potato leaf and stem tissues after pathogen infection. Salicylic acid, methyl jasmonate and abscisic acid could induce StLTPbl gene expression without significant difference between the upper and lower tissues. These abiotic elicitors could produce a long-lastingeffect on the StLTPbl during early stages of potato-R, solanacearum interaction. Differential expression of StLTPbl gene between resistance and susceptible potato genotypes in response to R. solanacearum suggests that this gene plays a key role in plant defense mechanisms.展开更多
基金supported by the China Forage and Grass Research System (CARS-35)the National Key Technology R&D Program of China (2011BAD17B01)
文摘Planting grass and legume mixtures on improved grasslands has the potential advantage of realizing both higher yields and lower environmental pollution by optimizing the balance between applied N fertilizer and the natural process of legume biological nitrogen fixation. However, the optimal level of N fertilization for grass-legume mixtures, to obtain the highest yield, quality, and contribution of N2 fixation, varies with species. A greenhouse pot experiment was conducted to study the temporal dynamics of N2 fixation of alfalfa （Medicago sativa L.） grown alone and in mixture with smooth bromegrass （Bromus inermis Leyss.） in response to the addition of fertilizer N. Three levels of N （0, 75, and 150 kg ha-1） were examined using 15N-labeled urea to evaluate N2 fixation via the 15N isotope dilution method. Treatments were designated NO （0.001 g per pot）, N75 （1.07 g per pot） and N150 （2.14 g per pot）. Alfalfa grown alone did not benefit from the addition of fertilizer N; dry matter was not significantly increased. In contrast, dry weight and N content of smooth bromegrass grown alone was increased significantly by N application. When grown as a mixture, smooth bromegrass biomass was increased significantly by N application, resulted in a decrease in alfalfa biomass. In addition, individual alfalfa plant dry weight （shoots＋roots） was significantly lower in the mixture than when grown alone at all N levels. Smooth bromegrass shoot and root dry weight were significantly higher when grown with alfalfa than when grown alone, regardless of N application level. When grown alone, alfalfa＇s N2 fixation was reduced with N fertilization （R2=0.9376,P=0.0057）. When grown in a mixture with smooth bromegrass, with 75 kg ha-1 of N fertilizer, the percentage of atmospheric N2 fixation contribution to total N in alfalfa （%Ndfa） had a maximum of 84.07 and 83.05% in the 2nd and 3rd harvests, respectively. Total 3-harvest %Ndfa was higher when alfalfa was grown in a mixture than when grown alone （shoots： ｜t｜=3.39, P=0.0096; root： ｜t｜=3.57, P=0.0073）. We believe this was due to smooth bromegrass being better able to absorb available soil N （due to its fibrous root system）, resulting inlower soil N availability and allowing alfalfa to develop an effective N2 fixing symbiosis prior to the 1st harvest. Once soil N levels were depleted, alfalfa was able to fix N2, resulting in the majority of its tissue N being derived from biological nitrogen fixation （BNF） in the 2nd and 3rd harvests. When grown in a mixture, with added N, alfalfa established an effective symbiosis earlier than when grown alone; in monoculture BNF did not contribute a significant portion of plant N in the N75 and N150 treatments, whereas in the mixture, BNF contributed 17.90 and 16.28% for these treatments respectively. Alfalfa has a higher BNF efficiency when grown in a mixture, initiating BNF earlier, and having higher N2 fixation due to less inhibition by soil-available N. For the greatest N-use-efficiency and sustainable production, grass-legume mixtures are recommended for imDrovino orasslands, usino a moderate amount of N fertilizer （75 kq N ha-l） to provide optimum benefits.
文摘A full-length cDNA of proteinase inhibitor gene with completed open reading frame of 116 amino acids was cloned from Ralstonia solanacearum （Rs） resistant potato leaves using the rapid amplification of cDNA ends （RACE） method and designated as StPI. BLAST search against NCBI showed that the StPI gene shared 89% identity with potato proteinase inhibitor I precursor in nucleotide and 74% in amino acid. Analysis of semi-quantitative RT-PCR indicated that this gene was induced by Rs as well as up-regulated by jasmonic acid （JA）. The StPI gene expression reached the highest level during 6-12 h post Rs-inoculation or JA-treatment, and then leveled off. Moreover, this gene was strongly induced by JA and its mRNA accumulation increased more quickly than that of Rs-inoculation. The StPI gene may play a role in potato resistance against Rs. The induction of StPI by Rs invasion may have a similar signal transduction pathway with JA treatment.
基金grateful to Ren Caihong(College of Life Science,Shanxi Normal University of China)for technical assistance.This work was supported by National 863 Program(2003AA207130)Natural Science Foundation of Shanxi Province of China(20051042).
文摘This study is to investigate the role of lipid transfer protein （LTP1） gene of potato （Solanum tuberosum） in bacterial wilt （Ralstonia solanacearum） resistance. A novel cDNA clone encoding nsLTP was isolated from cultivated potato （Solanum tuberosum） infected with R. solanacearum by 5＇-rapid amplification of cDNA ends （RACE）. The temporal and spatial expression of StLTPbl was studied during the early stages of potato-R, solanacearum interaction by reverse transcriptase PCR （RT-PCR） and Northern blotting. The sequence analysis of the cloned cDNA, named StLTPbl, showed 691 bp which encoded a type 1 nsLTP of 91 amino acids. Construction of a phylogenic tree showed that StLTPbl is well conserved in the coding region with high identity at the amino acid level with other Solanaceae nsLTPs. The temporal and spatial expression of StLTPbl was studied during the early stages of potato-R, solanacearum interaction. StLTPbl transcription is induced faster and transcripts accumulate to higher concentrations in resistant compared with susceptible genotypes by the pathogen. Dominant differences in the pathogen-induced gene expression pattern between the upper and lower leaves and stems were observed within the same genotypes. In situ hybridization results showed that the StLTPbl mRNA was localized in phloem cells of vascular tissues in potato leaf and stem tissues after pathogen infection. Salicylic acid, methyl jasmonate and abscisic acid could induce StLTPbl gene expression without significant difference between the upper and lower tissues. These abiotic elicitors could produce a long-lastingeffect on the StLTPbl during early stages of potato-R, solanacearum interaction. Differential expression of StLTPbl gene between resistance and susceptible potato genotypes in response to R. solanacearum suggests that this gene plays a key role in plant defense mechanisms.
