SUMMARY
Taxonomy: Bacteria; Proteobacteria, Gammaproteobacteria; Xanthomonadales; Xanthomonadaceae, Xanthomonas.
Microbiological properties: Gram‐negative, obligately aerobic, straight rods, motile ...by a single polar flagellum, yellow pigment.
Related species: X. campestris
,
X. axonopodis
,
X. oryzae
,
X. albilineans .
Host range: Affects Rutaceous plants, primarily Citrus spp., Fortunella spp., and Poncirus spp., world‐wide. Quarantined pathogen in many countries. Economically important hosts are cultivated orange, grapefruit, lime, lemon, pomelo and citrus rootstock.
Disease symptoms: On leaves, first appearance is as oily looking, 2–10 mm, similarly sized, circular spots, usually on the abaxial surface. On leaves, stems, thorns and fruit, circular lesions become raised and blister‐like, growing into white or yellow spongy pustules. These pustules then darken and thicken into a light tan to brown corky canker, which is rough to the touch. On stems, pustules may coalesce to split the epidermis along the stem length, and occasionally girdling of young stems may occur. Older lesions on leaves and fruit tend to have more elevated margins and are at times surrounded by a yellow chlorotic halo (that may disappear) and a sunken centre. Sunken craters are especially noticeable on fruit, but the lesions do not penetrate far into the rind. Defoliation and premature abscission of affected fruit occurs on heavily infected trees.
Useful websites: <http://www.biotech.ufl.edu/PlantContainment/canker.htm>; <http://cancer.lbi.ic.unicamp.br/xanthomonas/>
Plant immune response is associated with a large-scale transcriptional reprogramming, which is regulated by numerous transcription regulators such as the Elongator complex. Elongator is a ...multitasking protein complex involved in diverse cellular processes, including histone modification, DNA methylation, and tRNA modification. In recent years, Elongator is emerging as a key regulator of plant immune responses. However, characterization of Elongator's function in plant immunity has been conducted only in the model plant Arabidopsis thaliana. It is thus unclear whether Elongator's role in plant immunity is conserved in higher plants. The objective of this study is to characterize transgenic woodland strawberry (Fragaria vesca L.) overexpressing the Arabidopsis Elongator (AtELP) genes, AtELP3 and AtELP4, and to determine whether F. vesca carries a functional Elongator complex.
Transgenic F. vesca and Arabidopsis plants were produced via Agrobacterium-mediated genetic transformation and characterized by morphology, PCR, real-time quantitative PCR, and disease resistance test. The Student's t test was used to analyze the data.
Overexpression of AtELP3 and AtELP4 in F. vesca impacts plant growth and development and confers enhanced resistance to anthracnose crown rot, powdery mildew, and angular leaf spot, which are caused by the hemibiotrophic fungal pathogen Colletotrichum gloeosporioides, the obligate biotrophic fungal pathogen Podosphaera aphanis, and the hemibiotrophic bacterial pathogen Xanthomonas fragariae, respectively. Moreover, the F. vesca genome encodes all six Elongator subunits by single-copy genes with the exception of FvELP4, which is encoded by two homologous genes, FvELP4-1 and FvELP4-2. We show that FvELP4-1 complemented the Arabidopsis Atelp4/elo1-1 mutant, indicating that FvELP4 is biologically functional.
This is the first report on overexpression of Elongator genes in plants. Our results indicate that the function of Elongator in plant immunity is most likely conserved in F. vesca and suggest that Elongator genes may hold potential for helping mitigate disease severity and reduce the use of fungicides in strawberry industry.
Citrus canker disease is caused by five groups of Xanthomonas citri strains that are distinguished primarily by host range: three from Asia (A, A*, and A(w)) and two that form a phylogenetically ...distinct clade and originated in South America (B and C). Every X. citri strain carries multiple DNA fragments that hybridize with pthA, which is essential for the pathogenicity of wide-host-range X. citri group A strain 3213. DNA fragments that hybridized with pthA were cloned from a representative strain from all five groups. Each strain carried one and only one pthA homolog that functionally complemented a knockout mutation of pthA in 3213. Every complementing homolog was of identical size to pthA and carried 17.5 nearly identical, direct tandem repeats, including three new genes from narrow-host-range groups C (pthC), A(w) (pthAW), and A* (pthA*). Every noncomplementing paralog was of a different size; one of these was sequenced from group A* (pthA*-2) and was found to have an intact promoter and full-length reading frame but with 15.5 repeats. None of the complementing homologs nor any of the noncomplementing paralogs conferred avirulence to 3213 on grapefruit or suppressed avirulence of a group A* strain on grapefruit. A knockout mutation of pthC in a group C strain resulted in loss of pathogenicity on lime, but the strain was unaffected in ability to elicit an HR on grapefruit. This pthC- mutant was fully complemented by pthA, pthB, or pthC. Analysis of the predicted amino-acid sequences of all functional pthA homologs and nonfunctional paralogs indicated that the specific sequence of the 17th repeat may be essential for pathogenicity of X. citri on citrus.
Simple sequence repeats (SSRs or microsatellites) are frequently used as a robust, rapid, and relatively inexpensive means of genotyping. Recent reports in cultivated strawberry (Fragaria × ananassa) ...have identified a widely applicable set of SSRs that permits discrimination of closely-related genotypes. In the present study this same set of SSRs is analyzed in cultivars commonly grown in the state of Florida, as well as advanced breeding selections from the University of Florida program. Nine primer pairs have been used to produce discrete SSR patterns for all lines tested, including diagnostic sets that distinguish between closely-related cultivars and/or breeding selections. A comparison of markers to known pedigrees is presented, along with analysis of relative relatedness between lines studied. We also detail important technical considerations for transferability and limitations of these technologies between laboratories. The resulting genotype data for cultivars commonly used in Florida are accessible as supplemental data in graphic format and allow comparison with other cultivars. Users can thus select the most diagnostic SSRs to test the lines in question. These resources provide new tools for breeders and nurseries to authenticate genotypes, follow inheritance patterns and enforce patent protection. As important, this report underscores the strengths and weaknesses of applying the original methodologies to a different plant population in independent laboratories.
Strawberry (Fragaria spp.) is a valuable fruit crop as well as an outstanding system for studying functional genomics in plants. The goal of this study was to substantially increase and analyze the ...available expressed sequence information in the genus by examining the transcriptome of the cultivated strawberry (Fragaria × ananassa Duchesne). To maximize transcript diversity and discovery, plants representing an octoploid strawberry cultivar were subjected to a broad range of treatments. Plant materials were pooled by tissue type. cDNA pools were sequenced by the Roche‐454 GS‐FLX system and assembled into over 32,000 contigs. Predictions of cellular localization and function were made by associating assembled contigs to annotated homologs, and the tissue pool tags provided a means to assess the overall expression pattern for any given transcript. Contigs comprised of reads originating from only one organ type and those present equally in all plant organs were both identified. Bacterial and fungal sequences found in the strawberry samples provide a metagenomic survey of the microbial community of a greenhouse strawberry plant. This study utilized an innovative assembly strategy on pooled tissues, thus providing a foundation for developing tissue‐specific tools, an opportunity to identify alleles for marker‐assisted selection, a reference of strawberry gene annotations, and a basis for comparative transcriptomics between cultivated strawberry, its diploid ancestors, and the wider Rosaceae family.
Tiger grass Thysanolaena maxima (Roxb.) Kuntze is a popular ornamental grass grown throughout landscapes in South Florida. In the summer of 2006, a leaf spot was observed on tiger grass in the ...landscape and a commercial nursery in Homestead, FL. The causal agent of the leaf spot was isolated and characterized morphologically and molecularly as Exserohilum rostratum (Drechsler) Leonard & Suggs. At high inoculum densities, symptoms were apparent as early as 12 h after inoculation, and caused widespread necrosis. Germinating conidia of E. rostratum and appressoria were observed in direct association with lesions. This newly discovered disease could potentially have a dramatic effect on the aesthetic quality and salability of this landscape ornamental.
Phosphorus (P) is one of the 17 elements essential for plant growth and development, and is also a key component in some agrochemicals, such as phosphorous acid. Thus, there are two types of P ...closely associated with crop production. The similarity of terms such as phosphoric acid and phosphorous acid may create some confusion as to the actual content and efficacy of these products. This revised 7-page fact sheet explains what phosphorous acid is and examines both its fungicidal activity and nutrient value. Written by Asha M. Brunings, Guodong Liu, Eric H. Simonne, Shouan Zhang, Yuncong Li, and Lawrence E. Datnoff, and published by the UF Department of Horticultural Sciences, March 2012.
HS1010/HS254: Are Phosphorous and Phosphoric Acids Equal Phosphorous Sources for Plant Growth? (ufl.edu)
Phosphorus (P) is one of the 17 elements essential for plant growth and development, and is also a key component in some agrochemicals, such as phosphorous acid. Thus, there are two types of P ...closely associated with crop production. The similarity of terms such as phosphoric acid and phosphorous acid may create some confusion as to the actual content and efficacy of these products. This revised 7-page fact sheet explains what phosphorous acid is and examines both its fungicidal activity and nutrient value. Written by Asha M. Brunings, Guodong Liu, Eric H. Simonne, Shouan Zhang, Yuncong Li, and Lawrence E. Datnoff, and published by the UF Department of Horticultural Sciences, March 2012. HS1010/HS254: Are Phosphorous and Phosphoric Acids Equal Phosphorous Sources for Plant Growth? (ufl.edu)
Pathogen profile: Xanthomonas citri Brunings, Asha M; Gabriel, Dean W
Molecular plant pathology,
05/2003, Volume:
4, Issue:
3
Journal Article
Peer reviewed
Taxonomy:Bacteria; Proteobacteria, Gammaproteobacteria; Xanthomonadales; Xanthomonadaceae, Xanthomonas. Microbiological properties:Gram-negative, obligately aerobic, straight rods, motile by a single ...polar flagellum, yellow pigment. Related species:X. campestris X. axonopodis X. oryzaeX. albilineans. Host range:Affects Rutaceous plants, primarily Citrus Fortunella Poncirus Disease symptoms:On leaves, first appearance is as oily looking, 2-10 mm, similarly sized, circular spots, usually on the abaxial surface. On leaves, stems, thorns and fruit, circular lesions become raised and blister-like, growing into white or yellow spongy pustules. These pustules then darken and thicken into a light tan to brown corky canker, which is rough to the touch. On stems, pustules may coalesce to split the epidermis along the stem length, and occasionally girdling of young stems may occur. Older lesions on leaves and fruit tend to have more elevated margins and are at times surrounded by a yellow chlorotic halo (that may disappear) and a sunken centre. Sunken craters are especially noticeable on fruit, but the lesions do not penetrate far into the rind. Defoliation and premature abscission of affected fruit occurs on heavily infected trees. Useful websites:<http://www.biotech.ufl.edu/PlantContainment/canker.htm>; h ttp://cancer.lbi.ic.unicamp.br/xanthomonas/>
While growers are familiar with phosphorus-containing fertilizer, the abundance of terms, apparently similar (such as phosphoric acid and phosphorous acid), may create some confusion on the actual ...content and efficacy of these products. Some common phosphorus-containing compounds are listed in Table 1. Some claims found in commercial literature and product descriptions refer to phosphorous acid as a “supplemental fertilizer,” while others present it as a fungicide (Table 2). The purpose of this article is to explain what phosphorous acid is and to examine both the fungicidal activity and nutritional value of phosphorous acid. This document is HS1010, one of a series of the Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Publication date: April 2005. HS1010/HS254: Are Phosphorous and Phosphoric Acids Equal Phosphorous Sources for Plant Growth? (ufl.edu)
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