1
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Saxe HJ, Walawage SL, Balan B, Leslie CA, Brown PJ, Browne GT, Kluepfel DA, Westphal A, Dandekar AM. Transcriptomic Evidence of a Link between Cell Wall Biogenesis, Pathogenesis, and Vigor in Walnut Root and Trunk Diseases. Int J Mol Sci 2024; 25:931. [PMID: 38256004 PMCID: PMC10815794 DOI: 10.3390/ijms25020931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/29/2023] [Accepted: 01/08/2024] [Indexed: 01/24/2024] Open
Abstract
Crown gall disease (Agrobacterium tumefaciens), crown/root rot disease (Phytophthora spp.), root lesion disease (Pratylenchus vulnus) and tree vigor are key traits affecting the productivity and quality of walnuts in California. Unchallenged hybrid rootstocks were analyzed by RNA-seq to examine pre-formed factors affecting these traits. Enrichment analysis of the differentially expressed genes revealed that the increased expression of cell wall biogenesis-related genes plays a key role in susceptibility to A. tumefaciens, susceptibility to Phytophthora spp. and increased vigor. Analysis of the predicted subcellular loci of the encoded proteins revealed that many gene products associated with vigor and susceptibility were targeted to the plasma membrane and extracellular space, connecting these traits to sustaining barrier function. We observed that RNA processing and splicing, along with predicted nuclear targeting, were associated with resistance to A. tumefaciens, resistance to Phytophthora spp. and low vigor. Four genes within the J. microcarpa QTL region for resistance to A. tumefaciens and Phytophthora spp. were represented among our transcripts, with two of the genes being differentially expressed in association with resistance to A. tumefaciens and decreased vigor. No differential expression related to Phytophthora spp. or P. vulnus resistance was observed in this region. Additionally, the J. microcarpa haplotype expressed more transcripts associated with resistance to A. tumefaciens, Phytophthora spp. and low vigor, but not P. vulnus, than the J. regia haplotype. We also report unique and shared hormone and defense responses associated with each trait. This research suggests a link between cell wall biogenesis, vigor and critical root diseases of walnut.
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Affiliation(s)
- Houston J. Saxe
- Department of Plant Sciences, University of California, Davis, CA 95616, USA; (H.J.S.); (S.L.W.); (C.A.L.); (P.J.B.)
| | - Sriema L. Walawage
- Department of Plant Sciences, University of California, Davis, CA 95616, USA; (H.J.S.); (S.L.W.); (C.A.L.); (P.J.B.)
| | - Bipin Balan
- Department of Plant Sciences, University of California, Davis, CA 95616, USA; (H.J.S.); (S.L.W.); (C.A.L.); (P.J.B.)
| | - Charles A. Leslie
- Department of Plant Sciences, University of California, Davis, CA 95616, USA; (H.J.S.); (S.L.W.); (C.A.L.); (P.J.B.)
| | - Patrick J. Brown
- Department of Plant Sciences, University of California, Davis, CA 95616, USA; (H.J.S.); (S.L.W.); (C.A.L.); (P.J.B.)
| | - Gregory T. Browne
- United States Department of Agriculture’s Agricultural Research Service Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California, Davis, CA 95616, USA; (G.T.B.); (D.A.K.)
| | - Daniel A. Kluepfel
- United States Department of Agriculture’s Agricultural Research Service Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California, Davis, CA 95616, USA; (G.T.B.); (D.A.K.)
| | - Andreas Westphal
- Department of Nematology, University of California, Riverside, CA 92521, USA;
| | - Abhaya M. Dandekar
- Department of Plant Sciences, University of California, Davis, CA 95616, USA; (H.J.S.); (S.L.W.); (C.A.L.); (P.J.B.)
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Momayyezi M, Rippner DA, Duong FV, Raja PV, Brown PJ, Kluepfel DA, Earles JM, Forrestel EJ, Gilbert ME, McElrone AJ. Structural and functional leaf diversity lead to variability in photosynthetic capacity across a range of Juglans regia genotypes. Plant Cell Environ 2022; 45:2351-2365. [PMID: 35642731 PMCID: PMC9543909 DOI: 10.1111/pce.14370] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 05/17/2022] [Accepted: 05/28/2022] [Indexed: 06/15/2023]
Abstract
Similar to other cropping systems, few walnut cultivars are used as scion in commercial production. Germplasm collections can be used to diversify cultivar options and hold potential for improving crop productivity, disease resistance and stress tolerance. In this study, we explored the anatomical and biochemical bases of photosynthetic capacity and response to water stress in 11 Juglans regia accessions in the U.S. department of agriculture, agricultural research service (USDA-ARS) National Clonal Germplasm. Net assimilation rate (An ) differed significantly among accessions and was greater in lower latitudes coincident with higher stomatal and mesophyll conductances, leaf thickness, mesophyll porosity, gas-phase diffusion, leaf nitrogen and lower leaf mass and stomatal density. High CO2 -saturated assimilation rates led to increases in An under diffusional and biochemical limitations. Greater An was found in lower-latitude accessions native to climates with more frost-free days, greater precipitation seasonality and lower temperature seasonality. As expected, water stress consistently impaired photosynthesis with the highest % reductions in lower-latitude accessions (A3, A5 and A9), which had the highest An under well-watered conditions. However, An for A3 and A5 remained among the highest under dehydration. J. regia accessions, which have leaf structural traits and biochemistry that enhance photosynthesis, could be used as commercial scions or breeding parents to enhance productivity.
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Affiliation(s)
- Mina Momayyezi
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
| | | | - Fiona V. Duong
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
| | - Pranav V. Raja
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
| | - Patrick J. Brown
- Department of Plant SciencesUniversity of CaliforniaDavisCaliforniaUSA
| | | | - J. Mason Earles
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
| | | | | | - Andrew J. McElrone
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
- USDA‐ARS, Crops Pathology and Genetics Research UnitDavisCaliforniaUSA
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3
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Momayyezi M, Borsuk AM, Brodersen CR, Gilbert ME, Théroux‐Rancourt G, Kluepfel DA, McElrone AJ. Desiccation of the leaf mesophyll and its implications for CO 2 diffusion and light processing. Plant Cell Environ 2022; 45:1362-1381. [PMID: 35141930 PMCID: PMC9314819 DOI: 10.1111/pce.14287] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 01/18/2022] [Accepted: 01/24/2022] [Indexed: 05/09/2023]
Abstract
Leaves balance CO2 and radiative absorption while maintaining water transport to maximise photosynthesis. Related species with contrasting leaf anatomy can provide insights into inherent and stress-induced links between structure and function for commonly measured leaf traits for important crops. We used two walnut species with contrasting mesophyll anatomy to evaluate these integrated exchange processes under non-stressed and drought conditions using a combination of light microscopy, X-ray microCT, gas exchange, hydraulic conductance, and chlorophyll distribution profiles through leaves. Juglans regia had thicker palisade mesophyll, higher fluorescence in the palisade, and greater low-mesophyll porosity that were associated with greater gas-phase diffusion (gIAS ), stomatal and mesophyll (gm ) conductances and carboxylation capacity. More and highly-packed mesophyll cells and bundle sheath extensions (BSEs) in Juglans microcarpa led to higher fluorescence in the spongy and in proximity to the BSEs. Both species exhibited drought-induced reductions in mesophyll cell volume, yet the associated increases in porosity and gIAS were obscured by declines in biochemical activity that decreased gm . Inherent differences in leaf anatomy between the species were linked to differences in gas exchange, light absorption and photosynthetic capacity, and drought-induced changes in leaf structure impacted performance via imposing species-specific limitations to light absorption, gas exchange and hydraulics.
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Affiliation(s)
- Mina Momayyezi
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
| | - Aleca M. Borsuk
- School of the EnvironmentYale UniversityNew HavenConnecticutUSA
| | | | | | | | | | - Andrew J. McElrone
- Department of Viticulture and EnologyUniversity of CaliforniaDavisCaliforniaUSA
- USDA‐ARSCrops Pathology and Genetics Research UnitDavisCaliforniaUSA
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Ramasamy RK, Luo MC, Leslie CA, Velasco D, Ott N, McClean A, Dandekar AM, Aradhya M, Brown PJ, Browne GT, Kluepfel DA, Westphal A, Dvorak J. Co-located quantitative trait loci mediate resistance to Agrobacterium tumefaciens, Phytophthora cinnamomi, and P. pini in Juglans microcarpa × J. regia hybrids. Hortic Res 2021; 8:111. [PMID: 33931626 PMCID: PMC8087670 DOI: 10.1038/s41438-021-00546-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 02/16/2021] [Accepted: 03/26/2021] [Indexed: 05/05/2023]
Abstract
Soil-borne plant pathogens represent a serious threat that undermines commercial walnut (Juglans regia) production worldwide. Crown gall, caused by Agrobacterium tumefaciens, and Phytophthora root and crown rots, caused by various Phytophthora spp., are among the most devastating walnut soil-borne diseases. A recognized strategy to combat soil-borne diseases is adoption of resistant rootstocks. Here, resistance to A. tumefaciens, P. cinnamomi, and P. pini is mapped in the genome of Juglans microcarpa, a North American wild relative of cultivated walnut. Half-sib J. microcarpa mother trees DJUG 31.01 and DJUG 31.09 were crossed with J. regia cv. Serr, producing 353 and 400 hybrids, respectively. Clonally propagated hybrids were genotyped by sequencing to construct genetic maps for the two populations and challenged with the three pathogens. Resistance to each of the three pathogens was mapped as a major QTL on the long arm of J. microcarpa chromosome 4D and was associated with the same haplotype, designated as haplotype b, raising the possibility that the two mother trees were heterozygous for a single Mendelian gene conferring resistance to all three pathogens. The deployment of this haplotype in rootstock breeding will facilitate breeding of a walnut rootstock resistant to both crown gall and Phytophthora root and crown rots.
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Affiliation(s)
| | - Ming-Cheng Luo
- Department of Plant Sciences, University of California, Davis, USA
| | - Charles A Leslie
- Department of Plant Sciences, University of California, Davis, USA
| | - Dianne Velasco
- Department of Plant Sciences, University of California, Davis, USA
| | - Natalia Ott
- USDA-ARS Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California, Davis, USA
| | - Ali McClean
- USDA-ARS Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California, Davis, USA
| | | | - Mallikarjuna Aradhya
- National Clonal Germplasm Repository, USDA-ARS, University of California, Davis, USA
| | - Patrick J Brown
- Department of Plant Sciences, University of California, Davis, USA
| | - Gregory T Browne
- USDA-ARS Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California, Davis, USA
| | - Daniel A Kluepfel
- USDA-ARS Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California, Davis, USA
| | - Andreas Westphal
- Department of Nematology, University of California, Riverside, USA
| | - Jan Dvorak
- Department of Plant Sciences, University of California, Davis, USA.
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5
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Knipfer T, Bambach N, Hernandez MI, Bartlett MK, Sinclair G, Duong F, Kluepfel DA, McElrone AJ. Predicting Stomatal Closure and Turgor Loss in Woody Plants Using Predawn and Midday Water Potential. Plant Physiol 2020; 184:881-894. [PMID: 32764130 PMCID: PMC7536669 DOI: 10.1104/pp.20.00500] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 07/21/2020] [Indexed: 05/03/2023]
Abstract
Knowledge about physiological stress thresholds provides crucial information about plant performance and survival under drought. In this study, we report on the triphasic nature of the relationship between plant water potential (Ψ) at predawn and midday and describe a method that predicts Ψ at stomatal closure and turgor loss exclusively from this water potential curve (WP curve). The method is based on a piecewise linear regression model that was developed to predict the boundaries (termed Θ1 and Θ2) separating the three phases of the curve and corresponding slope values. The method was tested for three economically important woody species. For all species, midday Ψ was much more negative than predawn Ψ during phase I (mild drought), reductions in midday Ψ were minor while predawn Ψ continued to decline during phase II (moderate drought), and midday and predawn Ψ reached similar values during phase III (severe drought). Corresponding measurement of leaf gas exchange indicated that boundary Θ1 between phases I and II coincided with Ψ at stomatal closure. Data from pressure-volume curves demonstrated that boundary Θ2 between phases II and III predicted Ψ at leaf turgor loss. The WP curve method described here is an advanced application of the Scholander-type pressure chamber to categorize plant dehydration under drought into three distinct phases and to predict Ψ thresholds of stomatal closure and turgor loss.
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Affiliation(s)
- Thorsten Knipfer
- Department of Viticulture and Enology, University of California, Davis, California 95616
- Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Nicolas Bambach
- Department of Viticulture and Enology, University of California, Davis, California 95616
| | - M Isabel Hernandez
- Department of Viticulture and Enology, University of California, Davis, California 95616
| | - Megan K Bartlett
- Department of Viticulture and Enology, University of California, Davis, California 95616
| | - Gabriela Sinclair
- Department of Viticulture and Enology, University of California, Davis, California 95616
| | - Fiona Duong
- Department of Viticulture and Enology, University of California, Davis, California 95616
| | - Daniel A Kluepfel
- United States Department of Agriculture-Agricultural Research Service, Crops Pathology and Genetics Research Unit, Davis, California 95616
| | - Andrew J McElrone
- Department of Viticulture and Enology, University of California, Davis, California 95616
- United States Department of Agriculture-Agricultural Research Service, Crops Pathology and Genetics Research Unit, Davis, California 95616
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6
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Poret-Peterson AT, Sayed N, Glyzewski N, Forbes H, González-Orta ET, Kluepfel DA. Temporal Responses of Microbial Communities to Anaerobic Soil Disinfestation. Microb Ecol 2020; 80:191-201. [PMID: 31873773 PMCID: PMC7338823 DOI: 10.1007/s00248-019-01477-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 12/16/2019] [Indexed: 06/10/2023]
Abstract
Anaerobic soil disinfestation (ASD) is an organic amendment-based management tool for controlling soil-borne plant diseases and is increasingly used in a variety of crops. ASD results in a marked decrease in soil redox potential and other physicochemical changes, and a turnover in the composition of the soil microbiome. Mechanisms of ASD-mediated pathogen control are not fully understood, but appear to depend on the carbon source used to initiate the process and involve a combination of biological (i.e., release of volatile organic compounds) and abiotic (i.e., lowered pH, release of metal ions) factors. In this study, we examined how the soil microbiome changes over time in response to ASD initiated with rice bran, tomato pomace, or red grape pomace as amendments using growth chamber mesocosms that replicate ASD-induced field soil redox conditions. Within 2 days, the soil microbiome rapidly shifted from a diverse assemblage of taxa to being dominated by members of the Firmicutes for all ASD treatments, whereas control mesocosms maintained diverse and more evenly distributed communities. Rice bran and tomato pomace amendments resulted in microbial communities with similar compositions and trajectories that were different from red grape pomace communities. Quantitative PCR showed nitrogenase gene abundances were higher in ASD communities and tended to increase over time, suggesting the potential for altering soil nitrogen availability. These results highlight the need for temporal and functional studies to understand how pathogen suppressive microbial communities assemble and function in ASD-treated soils.
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Affiliation(s)
| | - Nada Sayed
- USDA-ARS Crops Pathology and Genetics Research Unit, University of California, Davis, USA
- University of California Davis Medical Center, Sacramento, CA, USA
| | - Nathaniel Glyzewski
- USDA-ARS Crops Pathology and Genetics Research Unit, University of California, Davis, USA
- Green Leaf Lab, Sacramento, CA, USA
| | - Holly Forbes
- USDA-ARS Crops Pathology and Genetics Research Unit, University of California, Davis, USA
| | - Enid T González-Orta
- Department of Biological Sciences, California State University, Sacramento, CA, USA
| | - Daniel A Kluepfel
- USDA-ARS Crops Pathology and Genetics Research Unit, University of California, Davis, USA
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7
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Knipfer T, Barrios-Masias FH, Cuneo IF, Bouda M, Albuquerque CP, Brodersen CR, Kluepfel DA, McElrone AJ. Variations in xylem embolism susceptibility under drought between intact saplings of three walnut species. Tree Physiol 2018; 38:1180-1192. [PMID: 29850910 DOI: 10.1093/treephys/tpy049] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 05/16/2018] [Indexed: 06/08/2023]
Abstract
A germplasm collection containing varied Juglans genotypes holds potential to improve drought resistance of plant materials for commercial production. We used X-ray computed microtomography to evaluate stem xylem embolism susceptibility/repair in relation to vessel anatomical features (size, arrangement, connectivity and pit characteristics) in 2-year-old saplings of three Juglans species. In vivo analysis revealed interspecific variations in embolism susceptibility among Juglans microcarpa, J. hindsii (both native to arid habitats) and J. ailantifolia (native to mesic habitats). Stem xylem of J. microcarpa was more resistant to drought-induced embolism as compared with J. hindsii and J. ailantifolia (differences in embolism susceptibility among older and current year xylem were not detected in any species). Variations in most vessel anatomical traits were negligible among the three species; however, we detected substantial interspecific differences in intervessel pit characteristics. As compared with J. hindsii and J. ailantifolia, low embolism susceptibility in J. microcarpa was associated with smaller pit size in larger diameter vessels, a smaller area of the shared vessel wall occupied by pits, lower pit frequency and no changes in pit characteristics as vessel diameters increased. Changes in amount of embolized vessels following 40 days of re-watering were minor in intact saplings of all three species highlighting that an embolism repair mechanism did not contribute to drought recovery. In conclusion, our data indicate that interspecific variations in drought-induced embolism susceptibility are associated with species-specific pit characteristics, and these traits may provide a future target for breeding efforts aimed at selecting walnut germplasm with improved drought resistance.
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Affiliation(s)
- Thorsten Knipfer
- Department of Viticulture & Enology, University of California, Davis, CA, USA
| | | | - Italo F Cuneo
- Department of Viticulture & Enology, University of California, Davis, CA, USA
| | - Martin Bouda
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA
| | | | - Craig R Brodersen
- School of Forestry and Environmental Studies, Yale University, New Haven, CT, USA
| | - Daniel A Kluepfel
- USDA-ARS, Crops Pathology and Genetics Research Unit, Davis, CA, USA
| | - Andrew J McElrone
- Department of Viticulture & Enology, University of California, Davis, CA, USA
- USDA-ARS, Crops Pathology and Genetics Research Unit, Davis, CA, USA
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Poret-Peterson AT, Bhatnagar S, McClean AE, Kluepfel DA. Draft Genome Sequence of Agrobacterium tumefaciens Biovar 1 Strain 186, Isolated from Walnut. Genome Announc 2017; 5:e01232-17. [PMID: 29146852 PMCID: PMC5690329 DOI: 10.1128/genomea.01232-17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 10/23/2017] [Indexed: 11/20/2022]
Abstract
Agrobacterium tumefaciens biovar 1 strain 186 was isolated from a walnut tree expressing crown gall symptoms. The draft genome sequence of this strain harbored genes for crown gall formation and will be useful for understanding its virulence on Paradox, the predominant hybrid rootstock used for the cultivation of English walnut in California.
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Affiliation(s)
- Amisha T Poret-Peterson
- USDA-ARS Crops Pathology and Genetics Research Unit, University of California, Davis, California, USA
| | - Srijak Bhatnagar
- Microbiology Graduate Group, University of California, Davis, California, USA
| | - Ali E McClean
- USDA-ARS Crops Pathology and Genetics Research Unit, University of California, Davis, California, USA
| | - Daniel A Kluepfel
- USDA-ARS Crops Pathology and Genetics Research Unit, University of California, Davis, California, USA
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9
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Knipfer T, Brodersen CR, Zedan A, Kluepfel DA, McElrone AJ. Patterns of drought-induced embolism formation and spread in living walnut saplings visualized using X-ray microtomography. Tree Physiol 2015; 35:744-55. [PMID: 26063708 DOI: 10.1093/treephys/tpv040] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 04/27/2015] [Indexed: 05/23/2023]
Abstract
Embolism formation and spread are dependent on conduit structure and xylem network connectivity. Detailed spatial analysis has been limited due to a lack of non-destructive methods to visualize these processes in living plants. We used synchrotron X-ray computed tomography (microCT) to visualize these processes in vivo for Juglans microcarpa Berl. saplings subjected to drought, and also evaluated embolism repair capability after re-watering. Cavitation was not detected in vivo until stem water potentials (Ψ(stem)) reached -2.2 MPa, and loss of stem hydraulic conductivity as derived from microCT images predicted that 50% of conductivity was lost at Ψ(stem) of ∼ -3.5 MPa; xylem vulnerability as determined with the centrifuge method was comparable only in the range of Ψ(stem) from -2.5 to -3.5 MPa. MicroCT images showed that cavitation appeared initially in isolated vessels not connected to other air-filled conduits. Once embolized vessels were present, multiple vessels in close proximity cavitated, and 3-D analysis along the stem axis revealed some connections between cavitated vessels. A tomography-derived automated xylem network analysis found that only 36% of vessels had one or more connections to other vessels. Cavitation susceptibility was related to vessel diameter, with large diameter vessels (>40 μm, mean diameter 25-30 μm) cavitating mainly under moderate stress (Ψ(stem) > -3 MPa) and small diameter vessels (<30 μm) under severe stress. After re-watering there was no evidence for short or longer term vessel refilling over 2 weeks despite a rapid recovery of plant water status. The low embolism susceptibility in 1-year-old J. microcarpa may aid sapling survival during establishment.
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Affiliation(s)
- Thorsten Knipfer
- Department of Viticulture and Enology, University of California, Davis, CA 95616, USA
| | - Craig R Brodersen
- School of Forestry and Environmental Studies, Yale University, 195 Prospect Street, New Haven, CT 06511, USA
| | - Amr Zedan
- Department of Viticulture and Enology, University of California, Davis, CA 95616, USA
| | - Daniel A Kluepfel
- US Department of Agriculture, Agricultural Research Service, Davis, CA 95616, USA
| | - Andrew J McElrone
- Department of Viticulture and Enology, University of California, Davis, CA 95616, USA US Department of Agriculture, Agricultural Research Service, Davis, CA 95616, USA
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10
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Yakabe LE, Parker SR, Kluepfel DA. Incidence of Agrobacterium tumefaciens Biovar 1 in and on 'Paradox' (Juglans hindsii × Juglans regia) Walnut Seed Collected from Commercial Nurseries. Plant Dis 2014; 98:766-770. [PMID: 30708636 DOI: 10.1094/pdis-07-13-0742-re] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The walnut rootstock 'Paradox' (Juglans hindsii × J. regia) is susceptible to Agrobacterium tumefaciens, which often results in a high incidence of crown gall in nursery or walnut production orchards. Though A. tumefaciens is susceptible to the commonly used preplant soil fumigants, crown gall incidence can rise above acceptable levels. We examined the ability of Paradox seed to acquire A. tumefaciens as a function of harvest method used prior to planting. Over a 2-year period at two participating commercial nurseries, Paradox seed were collected directly from the mother tree without contacting the soil or gathered after sitting on the orchard floor for up to 28 days. A. tumefaciens was never detected in or on the 2,650 seeds collected directly from the mother tree. Both virulent and avirulent A. tumefaciens strains were detected in and on the husk of nuts incubated on the orchard floor at a frequency directly proportional to the time spent on the orchard floor. Regardless of A. tumefaciens contamination in or on the husk, A. tumefaciens was never detected in the seed interior. Avoiding soilborne populations of A. tumefaciens at the time of seed collection will play an important role in managing crown gall.
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Affiliation(s)
- L E Yakabe
- United States Department of Agriculture-Agricultural Research Service Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California-Davis 95616
| | - S R Parker
- United States Department of Agriculture-Agricultural Research Service Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California-Davis 95616
| | - D A Kluepfel
- United States Department of Agriculture-Agricultural Research Service Crops Pathology and Genetics Research Unit, Department of Plant Pathology, University of California-Davis 95616
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11
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Yakabe LE, Parker SR, Kluepfel DA. Role of Systemic Agrobacterium tumefaciens Populations in Crown Gall Incidence on the Walnut Hybrid Rootstock 'Paradox'. Plant Dis 2012; 96:1415-1421. [PMID: 30727339 DOI: 10.1094/pdis-05-11-0364-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Greater than 75% of English walnut production in the United States occurs on the walnut rootstock Juglans hindsii × J. regia 'Paradox', which is highly susceptible to infection by Agrobacterium tumefaciens. When seed were germinated and grown in the presence of A. tumefaciens, in the absence of wounding, 94% of the seedlings exhibited tumors while 89% contained systemic A. tumefaciens populations. When seedlings were wound inoculated, A. tumefaciens established endophytic populations in stem tissue and often migrated from the site of infection. Distribution of A. tumefaciens in the stem was random and may exhibit seasonal variation. A. tumefaciens populations in root tissue were more readily detected than in stem tissue and may serve as a reservoir for subsequent infection of the aerial portions of the tree. Importantly, 7% of inoculated, asymptomatic seedlings contained endophytic populations of A. tumefaciens. In all, 17% of seedlings inoculated as seeds developed galls at secondary stem-wound sites. These results provide an ecological and epidemiological foundation upon which to modify existing tree-handling practices in both nursery and orchard production environments to manage crown gall incidence.
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Affiliation(s)
- L E Yakabe
- United States Department of Agriculture-Agricultural Research Service, Crops Pathology and Genetics Research Unit, Davis, CA 95616
| | - S R Parker
- United States Department of Agriculture-Agricultural Research Service, Crops Pathology and Genetics Research Unit, Davis, CA 95616
| | - D A Kluepfel
- United States Department of Agriculture-Agricultural Research Service, Crops Pathology and Genetics Research Unit, Davis, CA 95616
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Nyczepir AP, Kluepfel DA, Waldrop V, Wechter WP. Soil Solarization and Biological Control for Managing Mesocriconema xenoplax and Short Life in a Newly Established Peach Orchard. Plant Dis 2012; 96:1309-1314. [PMID: 30727154 DOI: 10.1094/pdis-05-11-0373-re] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The effects of soil solarization, with and without a Pseudomonas spp. cocktail or wheat rotation as alternatives to chemical control of Mesocriconema xenoplax, were investigated from 2004 to 2011. Preplant solarization and soil fumigation (67% methyl bromide + 33% chloropicrin mixture; henceforth, referred to as MBr) was initiated in 2004 in an orchard infested with M. xenoplax and a history of peach tree short life (PTSL). Plots consisted of nine treatments: (i) nonsolarized soil-alone, (ii) nonsolarized soil with bacteria cocktail (nonsolar-bacteria), (iii) nonsolarized soil with wheat (nonsolar-wheat), (iv) nonsolarized soil with bacteria cocktail and wheat (nonsolar-bacteria-wheat), (v) solarized soil-alone, (vi) solarized soil with bacteria cocktail solar-bacteria), (vii) solarized soil with wheat (solar-wheat), (viii) solarized soil with bacteria cocktail and wheat (solar-bacteria-wheat), and (ix) preplant MBr fumigation. Peach trees were planted into all plots in 2005. Nematode populations were suppressed 20 months longer after orchard establishment in solar-alone and solar-wheat plots than solar-bacteria and solar-bacteria-wheat plots. Pseudomonas spp. cocktails did not have a pronounced effect in suppressing M. xenoplax in this study. Fumigation effect on M. xenoplax population density dissipated 24 months after application. Solar-wheat-treated soil was as effective as preplant MBr fumigation in increasing tree survival from PTSL for at least 6 years after orchard establishment.
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Affiliation(s)
- A P Nyczepir
- Research Plant Pathologist (Nematologist), United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Southeastern Fruit and Tree Nut Research Laboratory, Byron, GA 31008
| | - D A Kluepfel
- Research Plant Pathologist, USDA-ARS, Crops Pathology and Genetics Research Unit, University of California, Davis 95616
| | - V Waldrop
- Chemist I, Clemson University, Department of Entomology, Soils, & Plant Sciences, Clemson, SC 29634
| | - W P Wechter
- Research Plant Pathologist, USDA-ARS, U. S. Vegetable Laboratory, Charleston, SC 29414
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Loper JE, Hassan KA, Mavrodi DV, Davis EW, Lim CK, Shaffer BT, Elbourne LDH, Stockwell VO, Hartney SL, Breakwell K, Henkels MD, Tetu SG, Rangel LI, Kidarsa TA, Wilson NL, van de Mortel JE, Song C, Blumhagen R, Radune D, Hostetler JB, Brinkac LM, Durkin AS, Kluepfel DA, Wechter WP, Anderson AJ, Kim YC, Pierson LS, Pierson EA, Lindow SE, Kobayashi DY, Raaijmakers JM, Weller DM, Thomashow LS, Allen AE, Paulsen IT. Comparative genomics of plant-associated Pseudomonas spp.: insights into diversity and inheritance of traits involved in multitrophic interactions. PLoS Genet 2012; 8:e1002784. [PMID: 22792073 PMCID: PMC3390384 DOI: 10.1371/journal.pgen.1002784] [Citation(s) in RCA: 393] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 05/10/2012] [Indexed: 12/11/2022] Open
Abstract
We provide here a comparative genome analysis of ten strains within the Pseudomonas fluorescens group including seven new genomic sequences. These strains exhibit a diverse spectrum of traits involved in biological control and other multitrophic interactions with plants, microbes, and insects. Multilocus sequence analysis placed the strains in three sub-clades, which was reinforced by high levels of synteny, size of core genomes, and relatedness of orthologous genes between strains within a sub-clade. The heterogeneity of the P. fluorescens group was reflected in the large size of its pan-genome, which makes up approximately 54% of the pan-genome of the genus as a whole, and a core genome representing only 45–52% of the genome of any individual strain. We discovered genes for traits that were not known previously in the strains, including genes for the biosynthesis of the siderophores achromobactin and pseudomonine and the antibiotic 2-hexyl-5-propyl-alkylresorcinol; novel bacteriocins; type II, III, and VI secretion systems; and insect toxins. Certain gene clusters, such as those for two type III secretion systems, are present only in specific sub-clades, suggesting vertical inheritance. Almost all of the genes associated with multitrophic interactions map to genomic regions present in only a subset of the strains or unique to a specific strain. To explore the evolutionary origin of these genes, we mapped their distributions relative to the locations of mobile genetic elements and repetitive extragenic palindromic (REP) elements in each genome. The mobile genetic elements and many strain-specific genes fall into regions devoid of REP elements (i.e., REP deserts) and regions displaying atypical tri-nucleotide composition, possibly indicating relatively recent acquisition of these loci. Collectively, the results of this study highlight the enormous heterogeneity of the P. fluorescens group and the importance of the variable genome in tailoring individual strains to their specific lifestyles and functional repertoire. We sequenced the genomes of seven strains of the Pseudomonas fluorescens group that colonize plant surfaces and function as biological control agents, protecting plants from disease. In this study, we demonstrated the genomic diversity of the group by comparing these strains to each other and to three other strains that were sequenced previously. Only about half of the genes in each strain are present in all of the other strains, and each strain has hundreds of unique genes that are not present in the other genomes. We mapped the genes that contribute to biological control in each genome and found that most of the biological control genes are in the variable regions of the genome, which are not shared by all of the other strains. This finding is consistent with our knowledge of the distinctive biology of each strain. Finally, we looked for new genes that are likely to confer antimicrobial traits needed to suppress plant pathogens, but have not been identified previously. In each genome, we discovered many of these new genes, which provide avenues for future discovery of new traits with the potential to manage plant diseases in agriculture or natural ecosystems.
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Affiliation(s)
- Joyce E Loper
- Agricultural Research Service, US Department of Agriculture, Corvallis, Oregon, United States of America.
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14
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Yakabe LE, Parker SR, Kluepfel DA. Cationic Surfactants: Potential Surface Disinfectants to Manage Agrobacterium tumefaciens Biovar 1 Contamination of Grafting Tools. Plant Dis 2012; 96:409-415. [PMID: 30727138 DOI: 10.1094/pdis-11-10-0839] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Nursery production of walnut seedlings is a 2-year process, during which crown gall, caused by Agrobacterium tumefaciens, often develops at grafting wounds. In this study, the spread of crown gall via contaminated tools and the efficacy of several disinfectants against A. tumefaciens were demonstrated. The cationic surfactants benzalkonium chloride (BC), cetyltrimethylammonium bromide (CTAB), and Physan 20 eliminated 100% of the A. tumefaciens population in water suspensions treated at 7, 5, and 2 ppm, respectively. Sodium hypochlorite eliminated 100% of the A. tumefaciens population at 0.5 ppm. Sodium hypochlorite efficacy, however, was reduced by 64% in the presence of total solids (0.7 g/ml) which are commonly found in field situations. At similar concentrations of total solids, the efficacy of cationic surfactants decreased, on average, by only 13%. The minimum effective treatment needed to eliminate A. tumefaciens on infested scalpels was a 5-s exposure to BC or CTAB at 5,000 ppm (0.5%). Infested scalpels treated with BC or CTAB at less than 5,000 ppm caused gall formation in 14 ± 7% of cuts made on Datura stramonium stems. This was significantly less than the tumor incidence (100%) in cuts made with inoculated blades not treated BC or CTAB.
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Affiliation(s)
- L E Yakabe
- United States Department of Agriculture-Agricultural Research Service Crops Pathology and Genetics Research Unit, Davis, CA
| | - S R Parker
- United States Department of Agriculture-Agricultural Research Service Crops Pathology and Genetics Research Unit, Davis, CA
| | - D A Kluepfel
- United States Department of Agriculture-Agricultural Research Service Crops Pathology and Genetics Research Unit, Davis, CA
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15
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McClean AE, Duerkop BA, Greenberg EP, Kluepfel DA. AHL signals induce rubrifacine production in a bruI mutant of Brenneria rubrifaciens. Phytopathology 2012; 102:195-203. [PMID: 22236075 DOI: 10.1094/phyto-04-11-0111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Several members of the bacterial genus Brenneria are pathogenic on different tree species. Cell-free extracts from the bacterial phytopathogens Brenneria rubrifaciens, B. salicis, and B. nigrifluens induced production of the red pigment rubrifacine in the B. rubrifaciens bruI insertional mutant Br-212. Analysis of the bruI locus identified an adjacent open reading frame, designated bruR, with homology to luxR. High-performance liquid chromatography and mass spectrometry analysis of ethyl acetate extracts from wild-type B. rubrifaciens and Escherichia coli expressing the bruI gene identified two acyl homoserine lactone (AHL) peaks, N-(3-oxohexanoyl)-homoserine lactone (3OC6HSL) and N-hexanoyl-homoserine lactone (C6HSL). Addition of synthetic 3OC6HSL and C6HSL at 10 μM to the bruI mutant, strain Br-212, induced rubrifacine production and the ability to elicit a hypersensitive reaction (HR) in tobacco leaves. Synthetic C6HSL was less effective at inducing pigment production than 3OC6HSL at 10 μM. The bruI mutant Br-212 did not produce detectable AHLs, indicating that C6HSL and 3OC6HSL are the major AHLs produced by this species. The AHLs N-heptanoyl-DL-homoserine lactone (C7HSL), N-octanoyl-DL-homoserine lactone (C8HSL), and N-(3-oxooctanoyl)-DL-homoserine lactone (3OC8HSL) also induced pigment production in Br-212 and restored its ability to elicit an HR in tobacco, suggesting that cross-talk with other bacterial species may be possible.
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Affiliation(s)
- Ali E McClean
- Crops Pathology and Genetics Research Unit, United States Department of Agriculture-Agricultural Research Service, Department of Plant Pathology, University of California, Davis, CA 95616, USA
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16
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McElrone AJ, Grant JA, Kluepfel DA. The role of tyloses in crown hydraulic failure of mature walnut trees afflicted by apoplexy disorder. Tree Physiol 2010; 30:761-72. [PMID: 20447983 DOI: 10.1093/treephys/tpq026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In the Central Valley of California, mature walnut trees afflicted with apoplexy disorder exhibit rapid and complete crown defoliation within a few weeks of symptom initiation. Symptoms are typically found throughout the entire crown and are initially expressed as wilting and chlorosis followed by scorching of leaves. Since the cause of apoplexy disorder is unknown, we set out to elucidate the water relations physiology underlying this condition. Stem water potential (Psi(s)) of healthy, asymptomatic trees remained high throughout the 2007 growing season, while that of apoplexy-afflicted trees decreased significantly with the onset of symptoms for both healthy-appearing and symptomatic portions of these trees. Psi(s)s were significantly reduced by at least 0.7 MPa in the lower, middle and upper portions of the symptomatic canopies compared with those from asymptomatic trees. Heat pulse velocities measured in the main trunk at three radial depths consistently decreased prior to the onset of symptoms and eventually reached zero with complete crown defoliation. Comparison of sap flow with predicted water use based on walnut evapotranspiration suggests that stomata of symptomatic trees were closing at higher evaporative demand prior to symptom formation. Specific hydraulic conductivity (K(s)) of symptomatic stems was significantly lower than that of asymptomatic stems, and no detectable K(s) could be measured on several of the symptomatic stem samples. However, shallow root K(s) did not significantly differ between symptomatic and asymptomatic trees, suggesting that hydraulic failure was isolated to the crown of these grafted trees. Light and scanning electron microscopy of stem and trunk sapwood revealed extensive tylose development in vessels throughout the crown of symptomatic trees. Analysis of the formation of tyloses on multiple dates revealed rapid development of these vessel occlusions in conjunction with visual symptom formation and dramatic decreases in sap flow. In 2008, tylose development was associated with elevated ethylene production in the active sapwood of symptomatic trees. The cause of elevated ethylene associated with tylose production and symptom formation is yet to be determined.
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Affiliation(s)
- Andrew J McElrone
- USDA-ARS, Crops Pathology and Genetics Research Unit, Davis, CA 95616, USA.
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17
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Abstract
Brenneria rubrifaciens produces a unique red pigment known as rubrifacine that has been hypothesized to play a role in pathogenesis on walnut. Analysis of DNA flanking the Tn5 insertion site in 20 rubrifacine minus (pig(-)) mutants identified three regions required for rubrifacine production. The first region was homologous to nonribosomal peptide synthetases (NRPS), the second was homologous to autoinducer synthase genes (expI homologs), and the third region was homologous to the slyA gene of Candidatus blochmania and Escherichia coli. Pigment production was not necessary for elicitation of the hypersensitive response (HR) in tobacco and had little impact on virulence in tissue-cultured walnut plants. The expI-interrupted mutants exhibited reduced virulence on walnut and were HR negative on tobacco. Pigment production was restored in Br-212 when grown in the presence of wild-type B. rubrifaciens, E. coli carrying the cloned expI-like gene, or introduction of the cloned wild-type copy of the expI-like gene. Two Brenneria spp., B. nigrifluens and B. salicis, also restored pigment production in Br-212. These results demonstrate that rubrifacine production and virulence of B. rubrifaciens on walnut are under the control of a quorum-sensing system and are sensitive to signal molecules from other Brenneria spp.
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Affiliation(s)
- Ali E McClean
- Crops Pathology and Genetics Research Unit, United States Department of Agriculture-Agricultural Research Service, 259 Hutchison Hall, USA
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18
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Robertson AE, Wechter WP, Denny TP, Fortnum BA, Kluepfel DA. Relationship between avirulence gene (avrA) diversity in Ralstonia solanacearum and bacterial wilt incidence. Mol Plant Microbe Interact 2004; 17:1376-84. [PMID: 15597743 DOI: 10.1094/mpmi.2004.17.12.1376] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bacterial wilt, caused by Ralstonia solanacearum, is a serious disease of tobacco in North and South Carolina. In contrast, the disease rarely occurs on tobacco in Georgia and Florida, although bacterial wilt is a common problem on tomato. We investigated whether this difference in disease incidence could be explained by qualitative characteristics of avirulence gene avrA in the R. solanacearum population in the southeastern United States. Sequence analysis established that wild-type avrA has a 792-bp open reading frame. Polymerase chain reaction (PCR) amplification of avrA from 139 R. solanacearum strains generated either 792-bp or approximately 960-bp DNA fragments. Strains that elicited a hypersensitive reaction (HR) on tobacco contained the 792-bp allele, and were pathogenic on tomato and avirulent on tobacco. All HR-negative strains generated a approximately 960-bp DNA fragment, and wilted both tomato and tobacco. The DNA sequence of avrA in six HR-negative strains revealed the presence of one of two putative miniature inverted-repeat transposable elements (MITEs): a 152-bp MITE between nucleotides 542 and 543, or a 170-bp MITE between nucleotides 461 and 462 or 574 and 575. Southern analysis suggested that the 170-bp MITE is unique to strains from the southeastern United States and the Caribbean. Mutated avrA alleles were present in strains from 96 and 75% of North and South Carolina sites, respectively, and only in 13 and 0% of the sites in Georgia and Florida, respectively. Introduction of the wildtype allele on a plasmid into four HR-negative strains reduced their virulence on both tobacco and tomato. Inactivation of avrA in an HR-positive, avirulent strain, resulted in a mutant that was weakly virulent on tobacco. Thus, the incidence of bacterial wilt of tobacco in the southeastern United States is partially explained by which avrA allele dominates the local R. solanacearum population.
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Affiliation(s)
- Alison E Robertson
- Department of Entomology, Soils and Plant Sciences, Clemson University, Clemson, SC 29634-0377, USA
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19
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Wechter WP, Begum D, Presting G, Kim JJ, Wing RA, Kluepfel DA. Physical mapping, BAC-end sequence analysis, and marker tagging of the soilborne nematicidal bacterium, Pseudomonas synxantha BG33R. OMICS 2002; 6:11-21. [PMID: 11881828 DOI: 10.1089/15362310252780807] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
A bacterial artificial chromosome (BAC) library was constructed for the genome of the rhizosphere-inhabiting fluorescent pseudomonad Pseudomonas synxantha BG33R. Three thousand BAC clones with an average insert size of 140 kbp and representing a 70-fold genomic coverage were generated and arrayed onto nylon membranes. EcoRI fingerprint analysis of 986 BAC clones generated 23 contigs and 75 singletons. Hybridization analysis allowed us to order the 23 contigs and condense them into a single contig, yielding an estimated genome size of 5.1 Mb for P. synxantha BG33R. A minimum-tile path of 47 BACs was generated and end-sequenced. The genetic loci involved in ring nematode egg-kill factor production in BG33R Tn5 mutants, 246 (vgrG homolog), 1122 (sensor kinase homolog), 1233 (UDP-galactose epimerase homolog), 1397 (ferrisiderophore receptor homolog), and 1917 (ribosomal subunit protein homolog), have been mapped onto the minimum-tile BAC library. Two of the genetic regions that flank Tn5 insertions in BG33R egg-kill-negative mutants 1233 and 1397 are separated by a single BAC clone. Fragments isolated by ligation-mediated PCR of the Tn5 mutagenized regions of 29 randomly selected, non-egg-kill-related, insertion mutants have been anchored onto the ordered physical map of P. synxantha.
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Affiliation(s)
- W P Wechter
- The Department of Plant Pathology and Physiology, Clemson University, South Carolina 29634-0377, USA
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Kluepfel DA, Nyczepir AP, Lawrence JE, Wechter WP, Leverentz B. Biological control of the phytoparasitic nematode Mesocriconema xenoplax on peach trees. J Nematol 2002; 34:120-123. [PMID: 19265918 PMCID: PMC2620548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023] Open
Abstract
Seven fluorescent Pseudomonas spp. capable of inhibiting reproduction of Mesocriconema xenoplax have been isolated from soil sites that suppress both nematode multiplication and Peach Tree Short Life (PTSL). One of these seven strains, Pseudomonas sp. BG33R, inhibits M. xenoplax multiplication in vivo and egg hatch in vitro. Mesocriconema xenoplax populations on peach seedlings inoculated with BG33R and planted into soil-solarized field plots remained at or below the economic threshold for nematicide treatment in South Carolina for nearly 18 months. Soil solarization alone induced a shift toward a microbial community that was suppressive to nematode multiplication. Additionally, five Tn5 mutants of BG33R, lacking the ability to kill eggs, have been generated. The Tn5 insertion site in each mutant has been cloned and sequenced. DNA sequence analysis has revealed a high degree of homology to several genes of interest because of their potential involvement in the production of the egg-kill factor. These Tn5 egg-kill negative mutants also no longer produce protease or salicylic acid while producing nearly twice the amount of fluorescent siderophore as the wild type parent.
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Abstract
ABSTRACT The southern corn rootworm, Diabrotica undecimpunctata subsp. howardi, a common and mobile insect pest, was shown to transmit the rhizobacte-rium Pseudomonas chlororaphis strain L11 between corn plants. Strain L11 has been genetically modified to contain the lacZY genes from Escherichia coli. It can reach high densities on roots and invade the roots and move into the foliage. D. undecimpunctata subsp. howardi became infested with L11 as larvae while feeding on roots of seed-inoculated corn and retained the bacteria through pupation, molting to the adult stage, and emergence from the soil. Bacterial densities on or in the insects increased 100-fold after they fed again as adults on L11-infested foliage. Adults retained the bacteria for at least 2 weeks after last exposure and could transmit L11 to new plants. The likelihood of transmission decreased with time since last exposure to L11, but increased with time spent on the new plants. This research demonstrates that rhizobacteria can escape the rhizosphere by moving in or onto foliage, where they can then be acquired and transmitted by insects. This transmission route may be common among naturally occurring rhizobacteria and facilitate the dispersal of both beneficial and harmful soilborne microorganisms.
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Abstract
Following inoculation onto seeds, the rhizobacterium Pseudomonas aureofaciens Ps3732RNL11 (L11), which contains the constituitively expressed lacZ and lacY genes from Escherichia coli, was recovered from the interior of aerial tissues of all 16 monocot and dicot plants tested, and the exterior of aerial surfaces of 15. In more detailed studies with corn, wheat, and broccoli, both Ps3732RNL11 and its nonengineered parent strain PS3732RN (RN) rapidly established large populations on all root systems and smaller densities within the aerial tissues, all of which persisted at stable levels throughout 12- to 23-day test periods. There were no differences in the behavior of L11 and RN on any of the three plant species. L11 invaded the aeriel tissues of corn in at least two distinct ways. First, it moved into the interior of leaves following inoculation of guttation drops, suggesting that the bacteria may contaminate the developing shoot prior to its emergence from the soil and then invade through natural openings. However, when this route was blocked by inoculating the roots after shoot emergence in either soil or hydroponic systems, the bacteria still invaded the aerial tissues within 24 h, suggesting direct vascular transport from the roots. Such bacterial movement is an important consideration in future field releases of both native and genetically modified rhizobacteria.Key words: rhizosphere, genetically engineered microorganism, Pseudomonas aureofaciens.
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Abstract
Adsorption of
Agrobacterium tumefaciens
cells to potato tuber disks reached equilibrium after coincubation for about 30 min. More than 10% of the number of bacteria bound at equilibrium were adsorbed within 30 s. Adsorption isotherms obtained at three temperatures showed that the heat of adsorption was nearly zero.
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Affiliation(s)
- D A Kluepfel
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611
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Kluepfel DA, Pueppke SG. Isotherm for Adsorption of
Agrobacterium tumefaciens
to Susceptible Potato (
Solanum tuberosum
L.) Tissues. Appl Environ Microbiol 1985; 49:1351-5. [PMID: 16346800 PMCID: PMC241727 DOI: 10.1128/aem.49.6.1351-1355.1985] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Potato tuber disks were submerged in suspensions containing 10
1
to 10
9
cells of
Agrobacterium tumefaciens
B6 per ml. After 60 min, the disks were rinsed and homogenized, and portions of the homogenates were plated to measure the number of adsorbed bacteria. At low initial bacterial concentrations (10
5
/ml), 5 to 23% of the bacteria adsorbed. At higher bacterial concentrations, the corresponding value was approximately 1.2%. Adsorption was a reversible equilibrium process. Binding saturation was not achieved, and adsorbed bacteria were confined to monolayers on the surfaces of tissue prepared for scanning electron microscopy. Adsorption of strain B6 to potato tuber tissues is described accurately by the Freundlich adsorption isotherm and may be a nonspecific phenomenon.
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Affiliation(s)
- D A Kluepfel
- Department of Plant Pathology, University of Florida, Gainesville, Florida 32611
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Pueppke SG, Kluepfel DA, Anand VK. Interaction of Agrobacterium with potato lectin and concanavalin A and its effect on tumor induction in potato. ACTA ACUST UNITED AC 1982. [DOI: 10.1016/0048-4059(82)90021-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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