Cadmium(Cd) contamination has posed an increasing challenge to environmental quality and food security. In recent years,phytoremediation has been particularly scrutinized because it is cost-effective and environmental...Cadmium(Cd) contamination has posed an increasing challenge to environmental quality and food security. In recent years,phytoremediation has been particularly scrutinized because it is cost-effective and environmentally friendly, especially the use of metal-hyperaccumulating plants to extract or mine heavy metals from polluted soils. Under Cd stress, responses of hyperaccumulator and non-hyperaccumulator plants differ in morphological responses and physiological processes such as photosynthesis and respiration,uptake, transport, and assimilation of minerals and nitrogen, and water uptake and transport, which contribute to their ability to accumulate and detoxify Cd. This review aims to provide a brief overview of the recent progresses in the differential responses of hyperaccumulator and non-accumulator plants to Cd toxicity in terms of growth and physiological processes. Such information might be useful in developing phytoremediation technology for contaminated soils.展开更多
Introducing specific microorganisms into the soil ecological system is an important strategy for improving nutrient use efficiency.Two pot experiments were conducted in the greenhouse from December 3, 2012 to January ...Introducing specific microorganisms into the soil ecological system is an important strategy for improving nutrient use efficiency.Two pot experiments were conducted in the greenhouse from December 3, 2012 to January 25, 2013(Experiment 1) and March 11 to April 23, 2013(Experiment 2) to evaluate the effect of nitrogen(N) source and inoculation with plant growth-promoting rhizobacteria(PGPR) on plant growth and N and phosphorus(P) uptake in tomato(Lycopersicon esculentum Mill.) grown on calcareous soils from South Florida, USA.Treatments included urea, controlled release urea(a controlled release fertilizer, CRF) each at low and high N rates and with or without inoculation of PGPR.A mixture of PGPR strains Bacillus amyloliquefaciens IN937 a and Bacillus pumilus T4 was applied to the soil during growing periods of tomato.Treatments with PGPR inoculation increased plant height compared to treatments without PGPR in both experiments.Inoculation with PGPR increased shoot dry weight and shoot N uptake for the same N rate and N source.In both experiments, only at high N rate, CRF and urea treatments with PGPR had significantly(P < 0.05)greater shoot biomass than those without PGPR.Only at high N rate, CRF treatment with PGPR significantly increased shoot N uptake by 39.0% and 10.3% compared to that without PGPR in Experiments 1 and 2, respectively.Meanwhile, presence of PGPR in the soil increased shoot P uptake for all treatments in Experiment 1 and for most treatments in Experiment 2.In Experiment 1, only at low N rate, CRF treatment with PGPR significantly increased shoot P uptake compared with that without PGPR.In Experiment2, a significant increase in shoot P uptake by inoculation of PGPR was only observed in CRF treatment at high N rate.Results from this study indicate that inoculation with PGPR may increase plant growth and N and P uptake by tomato grown on calcareous soils.However, the effect of PGPR varied and was influenced by many factors such as N source, N rate, and soil fertility.Further investigations are warranted to confirm the effect of PGPR under different soil conditions.展开更多
Enzyme activities have the potential to indicate biological functioning of soils. In this study, soil urease, dehydrogenase, acid phosphatase and invertase activities and fluorescein diacetate(FDA) hydrolysis were mea...Enzyme activities have the potential to indicate biological functioning of soils. In this study, soil urease, dehydrogenase, acid phosphatase and invertase activities and fluorescein diacetate(FDA) hydrolysis were measured in two red soils spiked with Pb2+ranging from 0 to 2 400 mg kg-1to relate the enzyme activity values to both plant growth and the levels of available and total Pb2+concentrations in soils, and to examine the potential use of soil enzymes to assess the degrees of Pb contamination. Soil samples were taken for enzyme activities assaying during 3 month's incubation and then after planting of celery(Apium graveolens L.) and Chinese cabbage(Brassica chinensis L.). Enzyme activities in the red soil derived from arenaceous rock(RAR) were generally lower than those in the red soil developed on Quaternary red earths(REQ). At high Pb2+loadings, in both incubation and greenhouse studies, urease activity and FDA hydrolysis were significantly inhibited. But there were no significant relationships between soil dehydrogenase, acid phosphatase or invertase activity and soil Pb2+loadings in both RAR and REQ soils. The growth of celery and Chinese cabbage increased soil urease activity and FDA hydrolysis, but had minimal effect on dehydrogenase and invertase activities. There were positive correlations between celery biomass and soil urease activity and FDA hydrolysis. These results demonstrate that urease activity and FDA hydrolysis are more sensitive to Pb2+than acid phosphatase, dehydrogenase and invertase activities in the RAR and REQ soils.展开更多
Huanglongbing(HLB)is the most destructive bacterial disease of citrus worldwide.While most citrus varieties are susceptible to HLB,Poncirus trifoliata,a close relative of Citrus,and some of its hybrids with Citrus are...Huanglongbing(HLB)is the most destructive bacterial disease of citrus worldwide.While most citrus varieties are susceptible to HLB,Poncirus trifoliata,a close relative of Citrus,and some of its hybrids with Citrus are tolerant to HLB.No specific HLB tolerance genes have been identified in P.trifoliata but recent studies have shown that constitutive disease resistance(CDR)genes were expressed at much higher levels in HLB-tolerant Poncirus hybrids and the expression of CDR genes was modulated by Candidatus Liberibacter asiaticus(CLas),the pathogen of HLB.The current study was undertaken to mine and characterize the CDR gene family in Citrus and Poncirus and to understand its association with HLB tolerance in Poncirus.We identified 17 CDR genes in two citrus genomes,deduced their structures,and investigated their phylogenetic relationships.We revealed that the expansion of the CDR family in Citrus seems to be due to segmental and tandem duplication events.Through genome resequencing and transcriptome sequencing,we identified eight CDR genes in the Poncirus genome(PtCDR1-PtCDR8).The number of SNPs was the highest in PtCDR2 and the lowest in PtCDR7.Most of the deletion and insertion events were observed in the UTR regions of Citrus and Poncirus CDR genes.PtCDR2 and PtCDR8 were in abundance in the leaf transcriptomes of two HLB-tolerant Poncirus genotypes and were also upregulated in HLB-tolerant,Poncirus hybrids as revealed by real-time PCR analysis.These two CDR genes seem to be good candidate genes for future studies of their role in citrus-CLas interactions.展开更多
Downy mildew(DM),caused by obligate parasitic oomycetes,is a destructive disease for a wide range of crops worldwide.Recent outbreaks of impatiens downy mildew(IDM)in many countries have caused huge economic losses.A ...Downy mildew(DM),caused by obligate parasitic oomycetes,is a destructive disease for a wide range of crops worldwide.Recent outbreaks of impatiens downy mildew(IDM)in many countries have caused huge economic losses.A system to reveal plant–pathogen interactions in the early stage of infection and quickly assess resistance/susceptibility of plants to DM is desired.In this study,we established an early and rapid system to achieve these goals using impatiens as a model.Thirty-two cultivars of Impatiens walleriana and I.hawkeri were evaluated for their responses to IDM at cotyledon,first/second pair of true leaf,and mature plant stages.All I.walleriana cultivars were highly susceptible to IDM.While all I.hawkeri cultivars were resistant to IDM starting at the first true leaf stage,many(14/16)were susceptible to IDM at the cotyledon stage.Two cultivars showed resistance even at the cotyledon stage.Histological characterization showed that the resistance mechanism of the I.hawkeri cultivars resembles that in grapevine and type II resistance in sunflower.By integrating full-length transcriptome sequencing(Iso-Seq)and RNA-Seq,we constructed the first reference transcriptome for Impatiens comprised of 48,758 sequences with an N50 length of 2060 bp.Comparative transcriptome and qRT-PCR analyses revealed strong candidate genes for IDM resistance,including three resistance genes orthologous to the sunflower gene RGC203,a potential candidate associated with DM resistance.Our approach of integrating early disease-resistance phenotyping,histological characterization,and transcriptome analysis lay a solid foundation to improve DM resistance in impatiens and may provide a model for other crops.展开更多
The cultivated strawberry(Fragaria×ananassa)is consumed worldwide for its flavor and nutritional benefits.Genetic analysis of commercially important traits in strawberry are important for the development of breed...The cultivated strawberry(Fragaria×ananassa)is consumed worldwide for its flavor and nutritional benefits.Genetic analysis of commercially important traits in strawberry are important for the development of breeding methods and tools for this species.Although several quantitative trait loci(QTL)have been previously detected for fruit quality and flowering traits using low-density genetic maps,clarity on the sub-genomic locations of these QTLs was missing.Recent discoveries in allo-octoploid strawberry genomics led to the development of the IStraw90 single-nucleotide polymorphism(SNP)array,enabling high-density genetic maps and finer resolution QTL analysis.In this study,breeder-specified traits were evaluated in the Eastern(Michigan)and Western(Oregon)United States for a common set of breeding populations during 2 years.Several QTLs were validated for soluble solids content(SSC),fruit weight(FWT),pH and titratable acidity(TA)using a pedigree-based QTL analysis approach.For fruit quality,a QTL for SSC on linkage group(LG)6A,a QTL for FWT on LG 2BII,a QTL for pH on LG 4CII and two QTLs for TA on LGs 2A and 5B were detected.In addition,a large-effect QTL for flowering was detected at the distal end of LG 4A,coinciding with the FaPFRU locus.Marker haplotype analysis in the FaPFRU region indicated that the homozygous recessive genotype was highly predictive of seasonal flowering.SNP probes in the FaPFRU region may help facilitate marker-assisted selection for this trait.展开更多
基金supported by the National Natural Science Foundation of China (No. 41501521)a scholarship from the University of Florida, USA
文摘Cadmium(Cd) contamination has posed an increasing challenge to environmental quality and food security. In recent years,phytoremediation has been particularly scrutinized because it is cost-effective and environmentally friendly, especially the use of metal-hyperaccumulating plants to extract or mine heavy metals from polluted soils. Under Cd stress, responses of hyperaccumulator and non-hyperaccumulator plants differ in morphological responses and physiological processes such as photosynthesis and respiration,uptake, transport, and assimilation of minerals and nitrogen, and water uptake and transport, which contribute to their ability to accumulate and detoxify Cd. This review aims to provide a brief overview of the recent progresses in the differential responses of hyperaccumulator and non-accumulator plants to Cd toxicity in terms of growth and physiological processes. Such information might be useful in developing phytoremediation technology for contaminated soils.
基金supported in part by the University of Florida Research Opportunity Seed Fund,USA(2013–2015)
文摘Introducing specific microorganisms into the soil ecological system is an important strategy for improving nutrient use efficiency.Two pot experiments were conducted in the greenhouse from December 3, 2012 to January 25, 2013(Experiment 1) and March 11 to April 23, 2013(Experiment 2) to evaluate the effect of nitrogen(N) source and inoculation with plant growth-promoting rhizobacteria(PGPR) on plant growth and N and phosphorus(P) uptake in tomato(Lycopersicon esculentum Mill.) grown on calcareous soils from South Florida, USA.Treatments included urea, controlled release urea(a controlled release fertilizer, CRF) each at low and high N rates and with or without inoculation of PGPR.A mixture of PGPR strains Bacillus amyloliquefaciens IN937 a and Bacillus pumilus T4 was applied to the soil during growing periods of tomato.Treatments with PGPR inoculation increased plant height compared to treatments without PGPR in both experiments.Inoculation with PGPR increased shoot dry weight and shoot N uptake for the same N rate and N source.In both experiments, only at high N rate, CRF and urea treatments with PGPR had significantly(P < 0.05)greater shoot biomass than those without PGPR.Only at high N rate, CRF treatment with PGPR significantly increased shoot N uptake by 39.0% and 10.3% compared to that without PGPR in Experiments 1 and 2, respectively.Meanwhile, presence of PGPR in the soil increased shoot P uptake for all treatments in Experiment 1 and for most treatments in Experiment 2.In Experiment 1, only at low N rate, CRF treatment with PGPR significantly increased shoot P uptake compared with that without PGPR.In Experiment2, a significant increase in shoot P uptake by inoculation of PGPR was only observed in CRF treatment at high N rate.Results from this study indicate that inoculation with PGPR may increase plant growth and N and P uptake by tomato grown on calcareous soils.However, the effect of PGPR varied and was influenced by many factors such as N source, N rate, and soil fertility.Further investigations are warranted to confirm the effect of PGPR under different soil conditions.
基金Supported by the China-EU Science&Technology Cooperation Program(No.2011DFA101222)
文摘Enzyme activities have the potential to indicate biological functioning of soils. In this study, soil urease, dehydrogenase, acid phosphatase and invertase activities and fluorescein diacetate(FDA) hydrolysis were measured in two red soils spiked with Pb2+ranging from 0 to 2 400 mg kg-1to relate the enzyme activity values to both plant growth and the levels of available and total Pb2+concentrations in soils, and to examine the potential use of soil enzymes to assess the degrees of Pb contamination. Soil samples were taken for enzyme activities assaying during 3 month's incubation and then after planting of celery(Apium graveolens L.) and Chinese cabbage(Brassica chinensis L.). Enzyme activities in the red soil derived from arenaceous rock(RAR) were generally lower than those in the red soil developed on Quaternary red earths(REQ). At high Pb2+loadings, in both incubation and greenhouse studies, urease activity and FDA hydrolysis were significantly inhibited. But there were no significant relationships between soil dehydrogenase, acid phosphatase or invertase activity and soil Pb2+loadings in both RAR and REQ soils. The growth of celery and Chinese cabbage increased soil urease activity and FDA hydrolysis, but had minimal effect on dehydrogenase and invertase activities. There were positive correlations between celery biomass and soil urease activity and FDA hydrolysis. These results demonstrate that urease activity and FDA hydrolysis are more sensitive to Pb2+than acid phosphatase, dehydrogenase and invertase activities in the RAR and REQ soils.
基金ZD acknowledges financial support of this study from the Citrus Research and Development Foundation,Inc.(CDRF)(Project#108766 and#105077)from the USDA-NIFA Citrus Disease Research and Extension(CDRE)Program(Grant No.2015-70016-23027).
文摘Huanglongbing(HLB)is the most destructive bacterial disease of citrus worldwide.While most citrus varieties are susceptible to HLB,Poncirus trifoliata,a close relative of Citrus,and some of its hybrids with Citrus are tolerant to HLB.No specific HLB tolerance genes have been identified in P.trifoliata but recent studies have shown that constitutive disease resistance(CDR)genes were expressed at much higher levels in HLB-tolerant Poncirus hybrids and the expression of CDR genes was modulated by Candidatus Liberibacter asiaticus(CLas),the pathogen of HLB.The current study was undertaken to mine and characterize the CDR gene family in Citrus and Poncirus and to understand its association with HLB tolerance in Poncirus.We identified 17 CDR genes in two citrus genomes,deduced their structures,and investigated their phylogenetic relationships.We revealed that the expansion of the CDR family in Citrus seems to be due to segmental and tandem duplication events.Through genome resequencing and transcriptome sequencing,we identified eight CDR genes in the Poncirus genome(PtCDR1-PtCDR8).The number of SNPs was the highest in PtCDR2 and the lowest in PtCDR7.Most of the deletion and insertion events were observed in the UTR regions of Citrus and Poncirus CDR genes.PtCDR2 and PtCDR8 were in abundance in the leaf transcriptomes of two HLB-tolerant Poncirus genotypes and were also upregulated in HLB-tolerant,Poncirus hybrids as revealed by real-time PCR analysis.These two CDR genes seem to be good candidate genes for future studies of their role in citrus-CLas interactions.
基金supported by grants from the Florida Department of Agriculture and Consumer Service(FDACS)Florida Specialty Crop Block Grant Program(FDACS contract#020705 to A.P.and Z.D.)the Fred C.Gloeckner Foundation,Inc.(Z.D.),and the USDA/NIFA hatch projects(Project#FLA-GCR-005065 and FLA-GCC-005507)(Z.D.)。
文摘Downy mildew(DM),caused by obligate parasitic oomycetes,is a destructive disease for a wide range of crops worldwide.Recent outbreaks of impatiens downy mildew(IDM)in many countries have caused huge economic losses.A system to reveal plant–pathogen interactions in the early stage of infection and quickly assess resistance/susceptibility of plants to DM is desired.In this study,we established an early and rapid system to achieve these goals using impatiens as a model.Thirty-two cultivars of Impatiens walleriana and I.hawkeri were evaluated for their responses to IDM at cotyledon,first/second pair of true leaf,and mature plant stages.All I.walleriana cultivars were highly susceptible to IDM.While all I.hawkeri cultivars were resistant to IDM starting at the first true leaf stage,many(14/16)were susceptible to IDM at the cotyledon stage.Two cultivars showed resistance even at the cotyledon stage.Histological characterization showed that the resistance mechanism of the I.hawkeri cultivars resembles that in grapevine and type II resistance in sunflower.By integrating full-length transcriptome sequencing(Iso-Seq)and RNA-Seq,we constructed the first reference transcriptome for Impatiens comprised of 48,758 sequences with an N50 length of 2060 bp.Comparative transcriptome and qRT-PCR analyses revealed strong candidate genes for IDM resistance,including three resistance genes orthologous to the sunflower gene RGC203,a potential candidate associated with DM resistance.Our approach of integrating early disease-resistance phenotyping,histological characterization,and transcriptome analysis lay a solid foundation to improve DM resistance in impatiens and may provide a model for other crops.
基金This research was funded through the USDA’s National Institute of Food and Agriculture—Specialty Crop Research Initiative project,‘RosBREED:Enabling Marker-Assisted Breeding in Rosaceae’(2009-51181-05808)‘RosBREED:Combining Disease Resistance and Horticultural Quality in New Rosaceous Cultivars’(2014-51181-22378).
文摘The cultivated strawberry(Fragaria×ananassa)is consumed worldwide for its flavor and nutritional benefits.Genetic analysis of commercially important traits in strawberry are important for the development of breeding methods and tools for this species.Although several quantitative trait loci(QTL)have been previously detected for fruit quality and flowering traits using low-density genetic maps,clarity on the sub-genomic locations of these QTLs was missing.Recent discoveries in allo-octoploid strawberry genomics led to the development of the IStraw90 single-nucleotide polymorphism(SNP)array,enabling high-density genetic maps and finer resolution QTL analysis.In this study,breeder-specified traits were evaluated in the Eastern(Michigan)and Western(Oregon)United States for a common set of breeding populations during 2 years.Several QTLs were validated for soluble solids content(SSC),fruit weight(FWT),pH and titratable acidity(TA)using a pedigree-based QTL analysis approach.For fruit quality,a QTL for SSC on linkage group(LG)6A,a QTL for FWT on LG 2BII,a QTL for pH on LG 4CII and two QTLs for TA on LGs 2A and 5B were detected.In addition,a large-effect QTL for flowering was detected at the distal end of LG 4A,coinciding with the FaPFRU locus.Marker haplotype analysis in the FaPFRU region indicated that the homozygous recessive genotype was highly predictive of seasonal flowering.SNP probes in the FaPFRU region may help facilitate marker-assisted selection for this trait.
