Huanglongbing(HLB)is the most devastating disease for citrus worldwide.Candidatus Liberibacter asiaticus(C Las),vectored by Asian citrus psyllid(ACP,Diaphorina citri Kuwayama),is the most common pathogen causing the d...Huanglongbing(HLB)is the most devastating disease for citrus worldwide.Candidatus Liberibacter asiaticus(C Las),vectored by Asian citrus psyllid(ACP,Diaphorina citri Kuwayama),is the most common pathogen causing the disease.Commercial citrus varieties are highly susceptible to HLB,whereas trifoliate orange(Poncirus trifoliata)is considered highly tolerant to HLB.An F1 segregating population and their parent trifoliate orange and sweet orange,which had been exposed to intense HLB pressure for three years,was evaluated for disease symptoms,ACP colonization,C Las titer and tree vigor repeatedly for two to three years.Trifoliate orange and sweet orange showed significant differences for most of the phenotypic traits,and the F1 population exhibited a large variation.A high-density SNP-based genetic map with 1402 markers was constructed for trifoliate orange,which exhibited high synteny and high coverage of its reference genome.A total of 26 quantitative trait locus(QTLs)were identified in four linkage groups LG-t6,LG-t7,LG-t8 and LG-t9,of which four QTL clusters exhibit a clear co-localization of QTLs associated with different traits.Through genome-wide analysis of gene expression in response to C Las infection in‘Flying Dragon’and‘Larger-Flower DPI-50-7’trifoliate orange,85 differentially expressed genes were found located within the QTL clusters.Among them,seven genes were classified as defense or immunity protein which exhibited the highest transcriptional change after C Las infection.Our results indicate a quantitative genetic nature of HLB tolerance and identified candidate genes that should be valuable for searching for genetic solutions to HLB through breeding or genetic engineering.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
Developing CRISPR/Cas9-mediated non-transgenic mutants in asexually propagated perennial crop plants is challenging but highly desirable.Here,we report a highly useful method using an Agrobacterium-mediated transient ...Developing CRISPR/Cas9-mediated non-transgenic mutants in asexually propagated perennial crop plants is challenging but highly desirable.Here,we report a highly useful method using an Agrobacterium-mediated transient CRISPR/Cas9 gene expression system to create non-transgenic mutant plants without the need for sexual segregation.We have also developed a rapid,cost-effective,and high-throughput mutant screening protocol based on Illumina sequencing followed by high-resolution melting(HRM)analysis.Using tetraploid tobacco as a model species and the phytoene desaturase(PDS)gene as a target,we successfully created and expediently identified mutant plants,which were verified as tetra-allelic mutants.We produced pds mutant shoots at a rate of 47.5%from tobacco leaf explants,without the use of antibiotic selection.Among these pds plants,17.2%were confirmed to be non-transgenic,for an overall non-transgenic mutation rate of 8.2%.Our method is reliable and effective in creating non-transgenic mutant plants without the need to segregate out transgenes through sexual reproduction.This method should be applicable to many economically important,heterozygous,perennial crop species that are more difficult to regenerate.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
Breeding crops for improved flavor is challenging due to the high cost of sensory evaluation and the difficulty of connecting sensory experience to chemical composition.The main goal of this study was to identify the ...Breeding crops for improved flavor is challenging due to the high cost of sensory evaluation and the difficulty of connecting sensory experience to chemical composition.The main goal of this study was to identify the chemical drivers of sweetness and consumer liking for fresh strawberries(Fragaria×ananassa).Fruit of 148 strawberry samples from cultivars and breeding selections were grown and harvested over seven years and were subjected to both sensory and chemical analyses.Each panel consisted of at least 100 consumers,resulting in more than 15,000 sensory data points per descriptor.Three sugars,two acids and 113 volatile compounds were quantified.Consumer liking was highly associated with sweetness intensity,texture liking,and flavor intensity,but not sourness intensity.Partial least square analyses revealed 20 volatile compounds that increased sweetness perception independently of sugars;18 volatiles that increased liking independently of sugars;and 15 volatile compounds that had positive effects on both.Machine learning-based predictive models including sugars,acids,and volatiles explained at least 25%more variation in sweetness and liking than models accounting for sugars and acids only.Volatile compounds such asγ-dodecalactone;5-hepten-2-one,6-methyl;and multiple medium-chain fatty acid esters may serve as targets for breeding or quality control attributes for strawberry products.A genetic association study identified two loci controlling ester production,both on linkage group 6 A.Co-segregating makers in these regions can be used for increasing multiple esters simultaneously.This study demonstrates a paradigm for improvement of fruit sweetness and flavor in which consumers drive the identification of the most important chemical targets,which in turn drives the discovery of genetic targets for marker-assisted breeding.展开更多
After the sequencing of citrus genomes,gene function annotation is becoming a new challenge.Gene coexpression analysis can be employed for function annotation using publicly available microarray data sets.In this stud...After the sequencing of citrus genomes,gene function annotation is becoming a new challenge.Gene coexpression analysis can be employed for function annotation using publicly available microarray data sets.In this study,230 sweet orange(Citrus sinensis)microarrays were used to construct seven coexpression networks,including one condition-independent and six condition-dependent(Citrus canker,Huanglongbing,leaves,flavedo,albedo,and flesh)networks.In total,these networks contain 37633 edges among 6256 nodes(genes),which accounts for 52.11%measurable genes of the citrus microarray.Then,these networks were partitioned into functional modules using the Markov Cluster Algorithm.Significantly enriched Gene Ontology biological process terms and KEGG pathway terms were detected for 343 and 60 modules,respectively.Finally,independent verification of these networks was performed using another expression data of 371 genes.This study provides new targets for further functional analyses in citrus.展开更多
Within large-fruited germplasm,fruit size is influenced by flat and globe shapes.Whereas flat fruits are smaller and retain better marketability,globe fruits are larger and more prone to cuticle disorders.Commercial h...Within large-fruited germplasm,fruit size is influenced by flat and globe shapes.Whereas flat fruits are smaller and retain better marketability,globe fruits are larger and more prone to cuticle disorders.Commercial hybrids are often developed from crosses between flat and globe shaped parents because flat shape is thought to be dominant and fruit size intermediate.The objectives of this study were to determine the genetic basis of flat/globe fruit shape in large-fruited fresh-market tomato germplasm and to characterize its effects on several fruit traits.Twenty-three advanced single plant selections from the Fla.8000×Fla.8111B cross were selectively genotyped using a genome-wide SNP array,and inclusive composite interval mapping identified a single locus on the upper arm of chromosome 12 associated with shape,which we termed globe.A 238-plant F 2 population and 69 recombinant inbred lines for this region from the same parents delimited globe to approximately 392-kilobases.A germplasm survey representing materials from multiple breeding programs demonstrated that the locus explains the flat/globe shape broadly.A single base insertion in an exon of Solyc12g006860,a gene annotated as a brassinosteroid hydroxylase,segregated completely with shape in all populations tested.CRISPR/Cas9 knock out plants confirmed this gene as underlying the globe locus.In silico analysis of the mutant allele of GLOBE among 595 wild and domesticated accessions suggested that the allele arose very late in the domestication process.Fruit measurements in three genetic backgrounds evidenced that globe impacts fruit size and several fruit shape attributes,pedicel length/width,and susceptibility of fruit to weather check.The mutant allele of GLOBE appears mostly recessive for all traits except fruit size where it acts additively.展开更多
Powdery mildew(PM)caused by Podosphaera aphanis is a major fungal disease of cultivated strawberry.Mildew Resistance Locus O(MLO)is a gene family described for having conserved seven-transmembrane domains.Induced loss...Powdery mildew(PM)caused by Podosphaera aphanis is a major fungal disease of cultivated strawberry.Mildew Resistance Locus O(MLO)is a gene family described for having conserved seven-transmembrane domains.Induced loss-of-function in specific MLO genes can confer durable and broad resistance against PM pathogens.However,the genomic structure and potential role of MLO genes for PM resistance have not been characterized yet in the octoploid cultivated strawberry.In the present study,MLO gene families were characterized in four diploid progenitor species(Fragaria vesca,F.iinumae,F.viridis,and F.nipponica)and octoploid cultivated(Fragaria×ananassa)strawberry,and potential sources of MLO-mediated susceptibility were identified.Twenty MLO sequences were identified in F.vesca and 68 identified in F.×ananassa.Phylogenetic analysis divided diploid and octoploid strawberry MLO genes into eight different clades,in which three FveMLO(MLO10,MLO17,and MLO20)and their twelve orthologs of FaMLO were grouped together with functionally characterized MLO genes conferring PM susceptibility.Copy number variations revealed differences in MLO composition among homoeologous chromosomes,supporting the distinct origin of each subgenome during the evolution of octoploid strawberry.Dissecting genomic sequence and structural variations in candidate FaMLO genes revealed their potential role associated with genetic controls and functionality in strawberry against PM pathogen.Furthermore,the gene expression profiling and RNAi silencing of putative FaMLO genes in response to the pathogen indicate the function in PM resistance.These results are a critical first step in understanding the function of strawberry MLO genes and will facilitate further genetic studies of PM resistance in cultivated strawberry.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
Petunia is a very important flower in the global floriculture industry and has played a critical role as a model in plant genetic studies.Owing to limited genetic variability in commercial germplasm,development of nov...Petunia is a very important flower in the global floriculture industry and has played a critical role as a model in plant genetic studies.Owing to limited genetic variability in commercial germplasm,development of novel petunia phenotypes and new varieties has become increasingly difficult.To enrich petunia germplasm and facilitate genetic improvement,it is important to explore genetic variation in progenitor species that may contain highly valuable genes/alleles.In this study,an interspecific recombinant inbred population(168 recombinant inbreds)derived from Petunia integrifolia×P.axillaris were phenotyped for days to anthesis(DTA),flower count(Flower_C),flower diameter(Flower_D),flower length(Flower_L),plant height(Plant_H),plant spread(Plant_S),and plant size(Plant_Z)in 2014 and 2015.Transgressive segregation was observed for all traits in both years.The broad-sense heritability on a 2-year basis varied from 0.38(Flower_C)to 0.82(Flower_L).Ten QTL were consistently identified in both years and by two mapping strategies[multiple QTL mapping(MQM)in MapQTL and inclusive composite interval mapping(ICIM)in IciMapping].Major QTL explained up to 30.2,35.5,and 47.1%of the total phenotypic variation for Plant_S,Flower_L,and Flower_D,respectively.These findings should be of significant values for introgression of desirable genes from wild petunias into commercial varieties and future genetic improvement of this important flower.展开更多
The cultivated strawberry(Fragaria×ananassa)is an allo-octoploid species,originating nearly 300 years ago from wild progenitors from the Americas.Since that time the strawberry has become the most widely cultivat...The cultivated strawberry(Fragaria×ananassa)is an allo-octoploid species,originating nearly 300 years ago from wild progenitors from the Americas.Since that time the strawberry has become the most widely cultivated fruit crop in the world,universally appealing due to its sensory qualities and health benefits.The recent publication of the first highquality chromosome-scale octoploid strawberry genome(cv.Camarosa)is enabling rapid advances in genetics,stimulating scientific debate and provoking new research questions.In this forward-looking review we propose avenues of research toward new biological insights and applications to agriculture.Among these are the origins of the genome,characterization of genetic variants,and big data approaches to breeding.Key areas of research in molecular biology will include the control of flowering,fruit development,fruit quality,and plant–pathogen interactions.In order to realize this potential as a global community,investments in genome resources must be continually augmented.展开更多
Faced with rapid population growth and fresh water scarcity, reuse of reclaimed water is growing worldwide and becoming an integral part of water resource management. Our objective was to determine the fate of nutrien...Faced with rapid population growth and fresh water scarcity, reuse of reclaimed water is growing worldwide and becoming an integral part of water resource management. Our objective was to determine the fate of nutrients, trace metals, bacteria, and legacy organic compounds (organochlorine pesticides) in the recycled water from five commercial nursery ponds in Florida. The pH of recycled water at all sites was 8.1 - 9.3, except one site (6.5), while the electrical conductivity (EC) was 0.31 - 0.36 dS/m. Concentrations of trace metals in recycled water were low: Fe (0.125 - 0.367 mg/L), Al (0.126 - 0.169 mg/L), B (0.104 - 0.153 mg/L), Zn (0.123 - 0.211 mg/L), and Mn (<0.111 mg/L). Total phosphorus (P) and total nitrogen (N) in the recycled water were 0.35 - 1.00 mg/L and 1.56 - 2.30 mg/L, respectively. Among organochlorine pesticides, endrin aldehyde was the only pesticide detected in all nursery recycled water ponds, with concentrations from 0.04 to 0.10 μg/L at four sites and 1.62 μg/L at one site. Other detected pesticides in recycled water were methoxychlor, endosulfan sulfate, dichlorodiphenyldichloroethylene (DDE) and α-chlorodane, with concentrations < 0.20 μg/L. Total coliforms and Escherichia coli (E. coli) in recycled water were 20 - 50 colony forming units (CFU)/100 mL. We conclude that the concentrations of various inorganic and organic compounds in recycled water are very low and do not appear to be problematic for irrigation purposes in Florida’s nursery recycled water ponds.展开更多
Modern cultivated caladiums(Caladium×hortulanum)are grown for their long-lasting and colorful leaves.Understanding the mode of inheritance for caladium leaf characteristics is critical for plant breeders to selec...Modern cultivated caladiums(Caladium×hortulanum)are grown for their long-lasting and colorful leaves.Understanding the mode of inheritance for caladium leaf characteristics is critical for plant breeders to select appropriate parents,predict progeny performance,estimate breeding population sizes needed,and increase breeding efficiencies.This study was conducted to determine the mode of inheritance of two leaf background colors(lemon and green)in caladium and to understand their relationships with four other important leaf characteristics including leaf shape,main vein color,spotting,and rugosity.Seven caladium cultivars and three breeding lines were used as parents in 19 crosses,and their progeny were phenotyped for segregation of leaf traits.Results showed that the two leaf background colors are controlled by a single nuclear locus,with two alleles,LEM and lem,which control the dominant lemon and the recessive green leaf background color,respectively.The lemon-colored cultivar‘Miss Muffet’and breeding lines UF-52 and UF-53 have a heterozygous genotype LEMlem.Chi-square tests showed that the leaf background color locus LEM is independent from the leaf shape locus F,but is tightly linked to three loci(S,V and RLF)controlling leaf spotting,main vein color,and rugosity in caladium.A linkage map that consists of four loci controlling major caladium leaf characteristics and extends~15 cM was developed based on the observed recombination frequencies.This is the first report on the mode of inheritance of leaf background colors in caladium and in the Araceae family.The information gained in this study will be very useful for caladium breeding and study of the inheritance of leaf colors in other ornamental aroids,an important group of ornamental plants in the world.展开更多
The primary goal of genomic selection is to increase genetic gains for complex traits by predicting performance of individuals for which phenotypic data are not available.The objective of this study was to experimenta...The primary goal of genomic selection is to increase genetic gains for complex traits by predicting performance of individuals for which phenotypic data are not available.The objective of this study was to experimentally evaluate the potential of genomic selection in strawberry breeding and to define a strategy for its implementation.Four clonally replicated field trials,two in each of 2 years comprised of a total of 1628 individuals,were established in 2013–2014 and 2014–2015.Five complex yield and fruit quality traits with moderate to low heritability were assessed in each trial.High-density genotyping was performed with the Affymetrix Axiom IStraw90 single-nucleotide polymorphism array,and 17479 polymorphic markers were chosen for analysis.Several methods were compared,including Genomic BLUP,Bayes B,Bayes C,Bayesian LASSO Regression,Bayesian Ridge Regression and Reproducing Kernel Hilbert Spaces.Cross-validation within training populations resulted in higher values than for true validations across trials.For true validations,Bayes B gave the highest predictive abilities on average and also the highest selection efficiencies,particularly for yield traits that were the lowest heritability traits.Selection efficiencies using Bayes B for parent selection ranged from 74%for average fruit weight to 34%for early marketable yield.A breeding strategy is proposed in which advanced selection trials are utilized as training populations and in which genomic selection can reduce the breeding cycle from 3 to 2 years for a subset of untested parents based on their predicted genomic breeding values.展开更多
Based on the former constructed ‘Tyr1’ locus genetic map in family 9145, from LB6-2 [Clementine mandarin (C. reticulata) × Hamlin orange (C. sinensis)] × Swingle citrumelo (C. paradise × P. trifoliata...Based on the former constructed ‘Tyr1’ locus genetic map in family 9145, from LB6-2 [Clementine mandarin (C. reticulata) × Hamlin orange (C. sinensis)] × Swingle citrumelo (C. paradise × P. trifoliata), 9 markers were chosen for application in evaluating their effectiveness in marker-assisted selection (MAS) for citrus rootstock breeding program from many F1 progeny of Poncirus trifoliata. As the mapping revealed that these markers were estimated within a range of 12.1 cM in the linkage group, and among them, SCO07 co-segregated with ‘Tyr1’, and 7A4R as the closest to ‘Tyr1’ with a distance of 1.5 cM, these markers were basically fitful to go MAS screening. The results of screening P. trifoliata F1 progeny indicated that all the markers were inherited in codominant fashion and most of them were heterozygous on PT (Pomery of P. trifoliata)., marker 4L17R/CfoI and 7A4(1407)/BfaI were proved to be consistently reliable for accurate scoring of genotypes and the revealed polymorphism was basically coincided with the citrus nematode resistant phenotype within tested populations. The polymorphic genotype with marker 4L17R/CfoI was found completely matched up with the phenotype of individuals that conferred high resistance to citrus nematode when the USDA hybrid rootstocks were screened. Utilization of these markers, especially the highly specific 4L17R/CfoI and 7A4(1407)/BfaI, should result in great benefit to world citrus industry for early selection in rootstock-breeding program.展开更多
Tomato packers often struggle to find ways to reuse the large volumes of wastewater generated during the tomato cleaning and sanitizing processes due to high transportation costs for off-site disposal and strict surfa...Tomato packers often struggle to find ways to reuse the large volumes of wastewater generated during the tomato cleaning and sanitizing processes due to high transportation costs for off-site disposal and strict surface water discharge regulations in Florida. Information about the composition of tomato packinghouse wastewater and the likely sources of major wastewater constituents might provide insights to develop environmentally sustainable practices for wastewater reuse. The objective of this study was to characterize the chemical composition of wastewater generated in tomato packinghouses. The wastewater samples were collected for 6 to 8 hours from dump tanks of two representative packinghouses at 30 minute intervals after start-up of packing operations during May-June 2009. Results showed that wastewater had high electrical conductivity (1.3 - 2.8 dS·m–1) and chloride (255 - 1125 mg·L–1) due to the use of chlorine as a sanitizer in the packinghouses. Concentrations of total phosphorus (P, 2.8 - 5.7 mg·L–1) and copper (Cu, 1.9 - 2.2 mg·L–1) in wastewater were elevated due to tomato cleaning and sanitizing. To reduce P and Cu concentrations, treatment or blending of wastewater may be needed before discharging wastewater to surface waters. Concentrations of P, potassium, calcium, magnesium, zinc, iron, and manganese were much higher in packinghouse 1 as compared to packinghouse 2 wastewater, probably due to the greater contact time of tomatoes with the dump tank water. Whereas concentrations of Cu were similar in both packinghouses wastewater. Greater concentrations of chemical constituents in the wastewater suggest that residues of pesticides, insecticides, and/or foliar-applied micronutrients on tomatoes may be the likely external sources of most constituents (especially P, Cu, and Zn) in wastewater.展开更多
The 360 feed and manure samples were collected from 150 animal farms in Jiangsu Province, China and analyzed for heavy metals. Concentrations of Zn and Cu in animal feeds were 15.9–2041.8 and undetected–392.1 mg/kg ...The 360 feed and manure samples were collected from 150 animal farms in Jiangsu Province, China and analyzed for heavy metals. Concentrations of Zn and Cu in animal feeds were 15.9–2041.8 and undetected–392.1 mg/kg respectively, while Hg, As, Pb, Cd, and Cr in all feeds were below 10 mg/kg. Concentrations of Cu, Zn, and Cr in animal manures were 8.4–1726, 39.5–11379, and 1.0–1602 mg/kg respectively, while As, Cd, Hg, and Pb were < 10 mg/kg. The concentration of Cu, Zn, As and Cr in animal feed and manure were positively correlated(p < 0.001), but the Cd, Hg, and Pb were not statistically correlated between the feed and the manure. Concentrations of Cu and Zn were highest in pig feed and manure, followed by poultry and dairy feeds and manures. During 1990– 2008, Cu, Zn, As, Cr, Cd contents increased by 771%, 410%, 420%, 220%, and 63% in pig manure, 212%, 95%, 200%, 791%, and –63% in dairy manure, and 181%, 197%, 1500%, 261, and 196% in poultry manure. Most of the increases occurred from 2002 to 2008, which reflects the extensive use of feed additives after 2002. In contrast, Pb and Hg in manures continuously decreased from 1990 to 2008. The results suggest that the heavy metal contents in animal manure have been greatly increased over 18 years and the contribution of manures to soil should be considered.展开更多
Tagetes erecta is an annual multifunctional plant which can be cultivated under a broad range of climatic conditions. Polyploidization and interspecific hybridization are applied to facilitate breeding cultivars of T....Tagetes erecta is an annual multifunctional plant which can be cultivated under a broad range of climatic conditions. Polyploidization and interspecific hybridization are applied to facilitate breeding cultivars of T. erecta with improved ornamental qualities. Colchicine treatment to the germinating seeds was proved to be a useful tool for chromosome doubling of the male sterile two-type line ‘M525AB', with the resulting frequency of polyploid seedlings ranging from 88.89%(following 0.05% w/v colchicine applied for a 3–6 h exposure period) to a maximum of100.00%(following 0.1% for 3–6 h, or 0.2% for 3 h). Morphological observation, stomatal size and density analysis, flow cytometric analysis and chromosome counting were conducted to identify the tetraploid plants. Distinctive morphological changes were observed in a notable proportion of polyploid plants. The colchicine-treated polyploid T. erecta plants showed dwarfed and more robust growth, thicker, larger and greener leaves, larger inflorescences and florets. The mutant plants identified through morphological observation all aligned as polyploid plants, thus morphological observation could be an effective method for the detection of polyploidy. The polyploid plants had significant larger stomata size over the abaxial leaf surface, whereas the density of stomata distribution was remarkably reduced. The survival rate of tetraploid cuttings(i.e. 38%)was greatly reduced compared to that of diploid plants. The fertility of tetraploid plants was also decreased, as shown by cross-pollination yields.Interspecific hybridizations between colchicine-induced tetraploid plants of a male sterile T. erecta line and the naturally tetraploid fully fertile Tagetes patula species resulted in hybrid progeny. Most of these hybrids displayed the dwarfed growth stature and compact, larger-flower morphology which is the typical ideotype of herbaceous flowers. Thus, polyploidization may be employed effectively as a means to facilitate interspecific hybridization, thereby contributing significantly to the improvement of quantitative traits of Tagetes spp.展开更多
基金supported by grants from the Citrus Research and Development Foundation,USA(Grant No.CRDF#15-010)the New Varieties Development and Management Corporation(NVDMC),on behalf of the Florida citrus industry,USA,the Fundamental Research Funds for the Central Universities,China(Grant No.2022CDJXY-004)from the USDA-NIFA-SCRI,USA(Grant No.2015-70016-2302).
文摘Huanglongbing(HLB)is the most devastating disease for citrus worldwide.Candidatus Liberibacter asiaticus(C Las),vectored by Asian citrus psyllid(ACP,Diaphorina citri Kuwayama),is the most common pathogen causing the disease.Commercial citrus varieties are highly susceptible to HLB,whereas trifoliate orange(Poncirus trifoliata)is considered highly tolerant to HLB.An F1 segregating population and their parent trifoliate orange and sweet orange,which had been exposed to intense HLB pressure for three years,was evaluated for disease symptoms,ACP colonization,C Las titer and tree vigor repeatedly for two to three years.Trifoliate orange and sweet orange showed significant differences for most of the phenotypic traits,and the F1 population exhibited a large variation.A high-density SNP-based genetic map with 1402 markers was constructed for trifoliate orange,which exhibited high synteny and high coverage of its reference genome.A total of 26 quantitative trait locus(QTLs)were identified in four linkage groups LG-t6,LG-t7,LG-t8 and LG-t9,of which four QTL clusters exhibit a clear co-localization of QTLs associated with different traits.Through genome-wide analysis of gene expression in response to C Las infection in‘Flying Dragon’and‘Larger-Flower DPI-50-7’trifoliate orange,85 differentially expressed genes were found located within the QTL clusters.Among them,seven genes were classified as defense or immunity protein which exhibited the highest transcriptional change after C Las infection.Our results indicate a quantitative genetic nature of HLB tolerance and identified candidate genes that should be valuable for searching for genetic solutions to HLB through breeding or genetic engineering.
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.
基金We thank the financial support from the USDA National Institute of Food and Agriculture SCRI(grant no.2015-70016-23027)the Florida Citrus Development Foundation(2016-001)+1 种基金the Genetically Modified Organisms Breeding Major Projects of China(2014ZX0801008B-001)The Connecticut-Storrs Agriculture Experimental Station,the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Innovative Research Project of JAAS(ZX-17-2006)also contributed financially to some experiments presented in this manuscript.
文摘Developing CRISPR/Cas9-mediated non-transgenic mutants in asexually propagated perennial crop plants is challenging but highly desirable.Here,we report a highly useful method using an Agrobacterium-mediated transient CRISPR/Cas9 gene expression system to create non-transgenic mutant plants without the need for sexual segregation.We have also developed a rapid,cost-effective,and high-throughput mutant screening protocol based on Illumina sequencing followed by high-resolution melting(HRM)analysis.Using tetraploid tobacco as a model species and the phytoene desaturase(PDS)gene as a target,we successfully created and expediently identified mutant plants,which were verified as tetra-allelic mutants.We produced pds mutant shoots at a rate of 47.5%from tobacco leaf explants,without the use of antibiotic selection.Among these pds plants,17.2%were confirmed to be non-transgenic,for an overall non-transgenic mutation rate of 8.2%.Our method is reliable and effective in creating non-transgenic mutant plants without the need to segregate out transgenes through sexual reproduction.This method should be applicable to many economically important,heterozygous,perennial crop species that are more difficult to regenerate.
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.
文摘Breeding crops for improved flavor is challenging due to the high cost of sensory evaluation and the difficulty of connecting sensory experience to chemical composition.The main goal of this study was to identify the chemical drivers of sweetness and consumer liking for fresh strawberries(Fragaria×ananassa).Fruit of 148 strawberry samples from cultivars and breeding selections were grown and harvested over seven years and were subjected to both sensory and chemical analyses.Each panel consisted of at least 100 consumers,resulting in more than 15,000 sensory data points per descriptor.Three sugars,two acids and 113 volatile compounds were quantified.Consumer liking was highly associated with sweetness intensity,texture liking,and flavor intensity,but not sourness intensity.Partial least square analyses revealed 20 volatile compounds that increased sweetness perception independently of sugars;18 volatiles that increased liking independently of sugars;and 15 volatile compounds that had positive effects on both.Machine learning-based predictive models including sugars,acids,and volatiles explained at least 25%more variation in sweetness and liking than models accounting for sugars and acids only.Volatile compounds such asγ-dodecalactone;5-hepten-2-one,6-methyl;and multiple medium-chain fatty acid esters may serve as targets for breeding or quality control attributes for strawberry products.A genetic association study identified two loci controlling ester production,both on linkage group 6 A.Co-segregating makers in these regions can be used for increasing multiple esters simultaneously.This study demonstrates a paradigm for improvement of fruit sweetness and flavor in which consumers drive the identification of the most important chemical targets,which in turn drives the discovery of genetic targets for marker-assisted breeding.
基金This work was supported by a grant from the Citrus Research and Development Foundation(CRDF-724).
文摘After the sequencing of citrus genomes,gene function annotation is becoming a new challenge.Gene coexpression analysis can be employed for function annotation using publicly available microarray data sets.In this study,230 sweet orange(Citrus sinensis)microarrays were used to construct seven coexpression networks,including one condition-independent and six condition-dependent(Citrus canker,Huanglongbing,leaves,flavedo,albedo,and flesh)networks.In total,these networks contain 37633 edges among 6256 nodes(genes),which accounts for 52.11%measurable genes of the citrus microarray.Then,these networks were partitioned into functional modules using the Markov Cluster Algorithm.Significantly enriched Gene Ontology biological process terms and KEGG pathway terms were detected for 343 and 60 modules,respectively.Finally,independent verification of these networks was performed using another expression data of 371 genes.This study provides new targets for further functional analyses in citrus.
基金supported by funding from USDA NIFA AFRI 2016-05951by a scholarship from the Fulbright Garcia-Robles program.
文摘Within large-fruited germplasm,fruit size is influenced by flat and globe shapes.Whereas flat fruits are smaller and retain better marketability,globe fruits are larger and more prone to cuticle disorders.Commercial hybrids are often developed from crosses between flat and globe shaped parents because flat shape is thought to be dominant and fruit size intermediate.The objectives of this study were to determine the genetic basis of flat/globe fruit shape in large-fruited fresh-market tomato germplasm and to characterize its effects on several fruit traits.Twenty-three advanced single plant selections from the Fla.8000×Fla.8111B cross were selectively genotyped using a genome-wide SNP array,and inclusive composite interval mapping identified a single locus on the upper arm of chromosome 12 associated with shape,which we termed globe.A 238-plant F 2 population and 69 recombinant inbred lines for this region from the same parents delimited globe to approximately 392-kilobases.A germplasm survey representing materials from multiple breeding programs demonstrated that the locus explains the flat/globe shape broadly.A single base insertion in an exon of Solyc12g006860,a gene annotated as a brassinosteroid hydroxylase,segregated completely with shape in all populations tested.CRISPR/Cas9 knock out plants confirmed this gene as underlying the globe locus.In silico analysis of the mutant allele of GLOBE among 595 wild and domesticated accessions suggested that the allele arose very late in the domestication process.Fruit measurements in three genetic backgrounds evidenced that globe impacts fruit size and several fruit shape attributes,pedicel length/width,and susceptibility of fruit to weather check.The mutant allele of GLOBE appears mostly recessive for all traits except fruit size where it acts additively.
基金This work was supported by the Florida Strawberry Research and Education Foundation(FSREF)the“Next-generation Disease Resistance Breeding and Management Solutions for Strawberry”under award no.2017-51181-26833.
文摘Powdery mildew(PM)caused by Podosphaera aphanis is a major fungal disease of cultivated strawberry.Mildew Resistance Locus O(MLO)is a gene family described for having conserved seven-transmembrane domains.Induced loss-of-function in specific MLO genes can confer durable and broad resistance against PM pathogens.However,the genomic structure and potential role of MLO genes for PM resistance have not been characterized yet in the octoploid cultivated strawberry.In the present study,MLO gene families were characterized in four diploid progenitor species(Fragaria vesca,F.iinumae,F.viridis,and F.nipponica)and octoploid cultivated(Fragaria×ananassa)strawberry,and potential sources of MLO-mediated susceptibility were identified.Twenty MLO sequences were identified in F.vesca and 68 identified in F.×ananassa.Phylogenetic analysis divided diploid and octoploid strawberry MLO genes into eight different clades,in which three FveMLO(MLO10,MLO17,and MLO20)and their twelve orthologs of FaMLO were grouped together with functionally characterized MLO genes conferring PM susceptibility.Copy number variations revealed differences in MLO composition among homoeologous chromosomes,supporting the distinct origin of each subgenome during the evolution of octoploid strawberry.Dissecting genomic sequence and structural variations in candidate FaMLO genes revealed their potential role associated with genetic controls and functionality in strawberry against PM pathogen.Furthermore,the gene expression profiling and RNAi silencing of putative FaMLO genes in response to the pathogen indicate the function in PM resistance.These results are a critical first step in understanding the function of strawberry MLO genes and will facilitate further genetic studies of PM resistance in cultivated strawberry.
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sponsored by USDA-SCRI grant 2011-51181-30666 and USDA-NIFA hatch projects FLA-GCR-005065 and FLA-GCC-005507.
文摘Petunia is a very important flower in the global floriculture industry and has played a critical role as a model in plant genetic studies.Owing to limited genetic variability in commercial germplasm,development of novel petunia phenotypes and new varieties has become increasingly difficult.To enrich petunia germplasm and facilitate genetic improvement,it is important to explore genetic variation in progenitor species that may contain highly valuable genes/alleles.In this study,an interspecific recombinant inbred population(168 recombinant inbreds)derived from Petunia integrifolia×P.axillaris were phenotyped for days to anthesis(DTA),flower count(Flower_C),flower diameter(Flower_D),flower length(Flower_L),plant height(Plant_H),plant spread(Plant_S),and plant size(Plant_Z)in 2014 and 2015.Transgressive segregation was observed for all traits in both years.The broad-sense heritability on a 2-year basis varied from 0.38(Flower_C)to 0.82(Flower_L).Ten QTL were consistently identified in both years and by two mapping strategies[multiple QTL mapping(MQM)in MapQTL and inclusive composite interval mapping(ICIM)in IciMapping].Major QTL explained up to 30.2,35.5,and 47.1%of the total phenotypic variation for Plant_S,Flower_L,and Flower_D,respectively.These findings should be of significant values for introgression of desirable genes from wild petunias into commercial varieties and future genetic improvement of this important flower.
基金funding from USDA National Institute of Food and Agriculture Specialty Crop Research Initiative projects[2014-51181-22376,2014-51181-22378]USDA National Institute of Food and Agriculture National Research Support Project 10+1 种基金NSF Plant Genome Research Program award#444573,NSF CIF21 Data infrastructure Building Blocks award#1443040USDA Hatch project 1014919,California Strawberry Commission,Florida Strawberry Growers Association,Washington Tree Fruit Research Commission,and Washington State University.
文摘The cultivated strawberry(Fragaria×ananassa)is an allo-octoploid species,originating nearly 300 years ago from wild progenitors from the Americas.Since that time the strawberry has become the most widely cultivated fruit crop in the world,universally appealing due to its sensory qualities and health benefits.The recent publication of the first highquality chromosome-scale octoploid strawberry genome(cv.Camarosa)is enabling rapid advances in genetics,stimulating scientific debate and provoking new research questions.In this forward-looking review we propose avenues of research toward new biological insights and applications to agriculture.Among these are the origins of the genome,characterization of genetic variants,and big data approaches to breeding.Key areas of research in molecular biology will include the control of flowering,fruit development,fruit quality,and plant–pathogen interactions.In order to realize this potential as a global community,investments in genome resources must be continually augmented.
文摘Faced with rapid population growth and fresh water scarcity, reuse of reclaimed water is growing worldwide and becoming an integral part of water resource management. Our objective was to determine the fate of nutrients, trace metals, bacteria, and legacy organic compounds (organochlorine pesticides) in the recycled water from five commercial nursery ponds in Florida. The pH of recycled water at all sites was 8.1 - 9.3, except one site (6.5), while the electrical conductivity (EC) was 0.31 - 0.36 dS/m. Concentrations of trace metals in recycled water were low: Fe (0.125 - 0.367 mg/L), Al (0.126 - 0.169 mg/L), B (0.104 - 0.153 mg/L), Zn (0.123 - 0.211 mg/L), and Mn (<0.111 mg/L). Total phosphorus (P) and total nitrogen (N) in the recycled water were 0.35 - 1.00 mg/L and 1.56 - 2.30 mg/L, respectively. Among organochlorine pesticides, endrin aldehyde was the only pesticide detected in all nursery recycled water ponds, with concentrations from 0.04 to 0.10 μg/L at four sites and 1.62 μg/L at one site. Other detected pesticides in recycled water were methoxychlor, endosulfan sulfate, dichlorodiphenyldichloroethylene (DDE) and α-chlorodane, with concentrations < 0.20 μg/L. Total coliforms and Escherichia coli (E. coli) in recycled water were 20 - 50 colony forming units (CFU)/100 mL. We conclude that the concentrations of various inorganic and organic compounds in recycled water are very low and do not appear to be problematic for irrigation purposes in Florida’s nursery recycled water ponds.
文摘Modern cultivated caladiums(Caladium×hortulanum)are grown for their long-lasting and colorful leaves.Understanding the mode of inheritance for caladium leaf characteristics is critical for plant breeders to select appropriate parents,predict progeny performance,estimate breeding population sizes needed,and increase breeding efficiencies.This study was conducted to determine the mode of inheritance of two leaf background colors(lemon and green)in caladium and to understand their relationships with four other important leaf characteristics including leaf shape,main vein color,spotting,and rugosity.Seven caladium cultivars and three breeding lines were used as parents in 19 crosses,and their progeny were phenotyped for segregation of leaf traits.Results showed that the two leaf background colors are controlled by a single nuclear locus,with two alleles,LEM and lem,which control the dominant lemon and the recessive green leaf background color,respectively.The lemon-colored cultivar‘Miss Muffet’and breeding lines UF-52 and UF-53 have a heterozygous genotype LEMlem.Chi-square tests showed that the leaf background color locus LEM is independent from the leaf shape locus F,but is tightly linked to three loci(S,V and RLF)controlling leaf spotting,main vein color,and rugosity in caladium.A linkage map that consists of four loci controlling major caladium leaf characteristics and extends~15 cM was developed based on the observed recombination frequencies.This is the first report on the mode of inheritance of leaf background colors in caladium and in the Araceae family.The information gained in this study will be very useful for caladium breeding and study of the inheritance of leaf colors in other ornamental aroids,an important group of ornamental plants in the world.
基金Financial support for this project was provided through the Florida Agricultural Experiment Station,the Florida Strawberry Growers Association,and the USDA/NIFA Specialty Crop Research Initiative project‘RosBREED:Combining disease resistance with horticultural quality in new rosaceous cultivars’under award number 2014-51181-22378.
文摘The primary goal of genomic selection is to increase genetic gains for complex traits by predicting performance of individuals for which phenotypic data are not available.The objective of this study was to experimentally evaluate the potential of genomic selection in strawberry breeding and to define a strategy for its implementation.Four clonally replicated field trials,two in each of 2 years comprised of a total of 1628 individuals,were established in 2013–2014 and 2014–2015.Five complex yield and fruit quality traits with moderate to low heritability were assessed in each trial.High-density genotyping was performed with the Affymetrix Axiom IStraw90 single-nucleotide polymorphism array,and 17479 polymorphic markers were chosen for analysis.Several methods were compared,including Genomic BLUP,Bayes B,Bayes C,Bayesian LASSO Regression,Bayesian Ridge Regression and Reproducing Kernel Hilbert Spaces.Cross-validation within training populations resulted in higher values than for true validations across trials.For true validations,Bayes B gave the highest predictive abilities on average and also the highest selection efficiencies,particularly for yield traits that were the lowest heritability traits.Selection efficiencies using Bayes B for parent selection ranged from 74%for average fruit weight to 34%for early marketable yield.A breeding strategy is proposed in which advanced selection trials are utilized as training populations and in which genomic selection can reduce the breeding cycle from 3 to 2 years for a subset of untested parents based on their predicted genomic breeding values.
基金supported in part by grants from the USDA NRICGP (9201765, 9600748)USDA/National Citrus Research Council (98012205)the Florida Citrus Production Research Advisory Council, USA(942-27)
文摘Based on the former constructed ‘Tyr1’ locus genetic map in family 9145, from LB6-2 [Clementine mandarin (C. reticulata) × Hamlin orange (C. sinensis)] × Swingle citrumelo (C. paradise × P. trifoliata), 9 markers were chosen for application in evaluating their effectiveness in marker-assisted selection (MAS) for citrus rootstock breeding program from many F1 progeny of Poncirus trifoliata. As the mapping revealed that these markers were estimated within a range of 12.1 cM in the linkage group, and among them, SCO07 co-segregated with ‘Tyr1’, and 7A4R as the closest to ‘Tyr1’ with a distance of 1.5 cM, these markers were basically fitful to go MAS screening. The results of screening P. trifoliata F1 progeny indicated that all the markers were inherited in codominant fashion and most of them were heterozygous on PT (Pomery of P. trifoliata)., marker 4L17R/CfoI and 7A4(1407)/BfaI were proved to be consistently reliable for accurate scoring of genotypes and the revealed polymorphism was basically coincided with the citrus nematode resistant phenotype within tested populations. The polymorphic genotype with marker 4L17R/CfoI was found completely matched up with the phenotype of individuals that conferred high resistance to citrus nematode when the USDA hybrid rootstocks were screened. Utilization of these markers, especially the highly specific 4L17R/CfoI and 7A4(1407)/BfaI, should result in great benefit to world citrus industry for early selection in rootstock-breeding program.
文摘Tomato packers often struggle to find ways to reuse the large volumes of wastewater generated during the tomato cleaning and sanitizing processes due to high transportation costs for off-site disposal and strict surface water discharge regulations in Florida. Information about the composition of tomato packinghouse wastewater and the likely sources of major wastewater constituents might provide insights to develop environmentally sustainable practices for wastewater reuse. The objective of this study was to characterize the chemical composition of wastewater generated in tomato packinghouses. The wastewater samples were collected for 6 to 8 hours from dump tanks of two representative packinghouses at 30 minute intervals after start-up of packing operations during May-June 2009. Results showed that wastewater had high electrical conductivity (1.3 - 2.8 dS·m–1) and chloride (255 - 1125 mg·L–1) due to the use of chlorine as a sanitizer in the packinghouses. Concentrations of total phosphorus (P, 2.8 - 5.7 mg·L–1) and copper (Cu, 1.9 - 2.2 mg·L–1) in wastewater were elevated due to tomato cleaning and sanitizing. To reduce P and Cu concentrations, treatment or blending of wastewater may be needed before discharging wastewater to surface waters. Concentrations of P, potassium, calcium, magnesium, zinc, iron, and manganese were much higher in packinghouse 1 as compared to packinghouse 2 wastewater, probably due to the greater contact time of tomatoes with the dump tank water. Whereas concentrations of Cu were similar in both packinghouses wastewater. Greater concentrations of chemical constituents in the wastewater suggest that residues of pesticides, insecticides, and/or foliar-applied micronutrients on tomatoes may be the likely external sources of most constituents (especially P, Cu, and Zn) in wastewater.
基金supported by the National Natural Science Foundation of China(No.41371319)the Special Funds for Enviro-Scientific Research(No.2013467036)the Agro-Scientific Research in the Public Interest(No.200903011)
文摘The 360 feed and manure samples were collected from 150 animal farms in Jiangsu Province, China and analyzed for heavy metals. Concentrations of Zn and Cu in animal feeds were 15.9–2041.8 and undetected–392.1 mg/kg respectively, while Hg, As, Pb, Cd, and Cr in all feeds were below 10 mg/kg. Concentrations of Cu, Zn, and Cr in animal manures were 8.4–1726, 39.5–11379, and 1.0–1602 mg/kg respectively, while As, Cd, Hg, and Pb were < 10 mg/kg. The concentration of Cu, Zn, As and Cr in animal feed and manure were positively correlated(p < 0.001), but the Cd, Hg, and Pb were not statistically correlated between the feed and the manure. Concentrations of Cu and Zn were highest in pig feed and manure, followed by poultry and dairy feeds and manures. During 1990– 2008, Cu, Zn, As, Cr, Cd contents increased by 771%, 410%, 420%, 220%, and 63% in pig manure, 212%, 95%, 200%, 791%, and –63% in dairy manure, and 181%, 197%, 1500%, 261, and 196% in poultry manure. Most of the increases occurred from 2002 to 2008, which reflects the extensive use of feed additives after 2002. In contrast, Pb and Hg in manures continuously decreased from 1990 to 2008. The results suggest that the heavy metal contents in animal manure have been greatly increased over 18 years and the contribution of manures to soil should be considered.
基金supported by grants from the National Natural Science Foundation of China (31201647, 31672181)
文摘Tagetes erecta is an annual multifunctional plant which can be cultivated under a broad range of climatic conditions. Polyploidization and interspecific hybridization are applied to facilitate breeding cultivars of T. erecta with improved ornamental qualities. Colchicine treatment to the germinating seeds was proved to be a useful tool for chromosome doubling of the male sterile two-type line ‘M525AB', with the resulting frequency of polyploid seedlings ranging from 88.89%(following 0.05% w/v colchicine applied for a 3–6 h exposure period) to a maximum of100.00%(following 0.1% for 3–6 h, or 0.2% for 3 h). Morphological observation, stomatal size and density analysis, flow cytometric analysis and chromosome counting were conducted to identify the tetraploid plants. Distinctive morphological changes were observed in a notable proportion of polyploid plants. The colchicine-treated polyploid T. erecta plants showed dwarfed and more robust growth, thicker, larger and greener leaves, larger inflorescences and florets. The mutant plants identified through morphological observation all aligned as polyploid plants, thus morphological observation could be an effective method for the detection of polyploidy. The polyploid plants had significant larger stomata size over the abaxial leaf surface, whereas the density of stomata distribution was remarkably reduced. The survival rate of tetraploid cuttings(i.e. 38%)was greatly reduced compared to that of diploid plants. The fertility of tetraploid plants was also decreased, as shown by cross-pollination yields.Interspecific hybridizations between colchicine-induced tetraploid plants of a male sterile T. erecta line and the naturally tetraploid fully fertile Tagetes patula species resulted in hybrid progeny. Most of these hybrids displayed the dwarfed growth stature and compact, larger-flower morphology which is the typical ideotype of herbaceous flowers. Thus, polyploidization may be employed effectively as a means to facilitate interspecific hybridization, thereby contributing significantly to the improvement of quantitative traits of Tagetes spp.
