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Genetic Mapping of Downy and Powdery Mildew Resistances and Characterization of CsSGR-Dependent Broad-Spectrum Disease Resistance in Cucumber (Cucumis sativus L.).

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Genetic Mapping of Downy and Powdery Mildew Resistances and Characterization of CsSGR-Dependent Broad-Spectrum Disease Resistance in Cucumber (Cucumis sativus L.)./
作者:	Tan, Junyi.
面頁冊數:	1 online resource (208 pages)
附註:	Source: Dissertations Abstracts International, Volume: 84-01, Section: B.
Contained By:	Dissertations Abstracts International84-01B.
標題:	Horticulture. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29255718click for full text (PQDT)
ISBN:	9798834033431

Genetic Mapping of Downy and Powdery Mildew Resistances and Characterization of CsSGR-Dependent Broad-Spectrum Disease Resistance in Cucumber (Cucumis sativus L.).
Tan, Junyi.

Genetic Mapping of Downy and Powdery Mildew Resistances and Characterization of CsSGR-Dependent Broad-Spectrum Disease Resistance in Cucumber (Cucumis sativus L.). - 1 online resource (208 pages)

Source: Dissertations Abstracts International, Volume: 84-01, Section: B.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2022.

Includes bibliographical references

Downy mildew (DM) caused by the oomycete pathogen Pseudoperonospora cubensis is an important disease of cucumber and other cucurbits. The effective protection conferred by a recessive resistance locus dm1 originated from the Indian germplasm line PI 197087 lasted for more than 50 years until the new stain(s) emerged in 2004. So far, control of DM in the field relies mainly on the application of fungicides. Some studies reveal that P. cubensis is a pathogenic organism that is prone to develop fungicide resistance. It is important to develop cucumber lines providing more effective and durable resistance to the dynamic pathogen populations in the field. Previous studies identified multiple quantitative traits loci (QTL) for DM resistance in the cucumber inbred line WI7088D (a selection from PI 197088) including the major-effect QTL dm5.3 on cucumber chromosome 5. Therefore, the first of objective in this thesis research was to fine map dm5.3. A BC4F2:3 NIL segregating population for dm5.3 was developed in the 9930 (susceptible) genetic background, which was genotyped using 21 SNPs, Indels, and SSR markers and phenotyped for their responses to DM inoculations under multiple environments. The dm5.3 locus was eventually narrowed into a 144kb region with 12 annotated genes. The analysis of allelic diversity and gene expression patterns supported CsGy5G027140 as the most likely candidate gene for dm5.3, which encodes a sigma factor binding protein (CsSIB1). Powdery mildew (PM) caused by the ascomycete fungal pathogen Podosphaera xanthii is one of the important diseases of cucumber and other cucurbits. A previous study identified four quantitative traits loci (QTL) for PM resistance WI7088D including the major-effect QTL pm5.3 co-localized with major-effect DM resistance QTL dm5.3, but their relationship is unknown. Thus, the second objective of this thesis project was to identify the candidate gene for pm5.3. Fine genetic mapping using the same NIL-derived segregating population for dm5.3 delimited the pm5.3 locus into a 211kb region with 27 annotated genes. CsGy5G026660, that encodes an MLO-like protein, is a possible candidate for pm5.3. Downy mildew (DM), anthracnose (AR), and angular leaf spot (ALS) are three major cucumber diseases. Previous studies found that a loss-of-function mutation inside the cucumber STAYGREEN (CsSGR) gene underlying the dm1/cla/psl locus confers broad-spectrum and durable resistances against three pathogens with different life styles. However, the molecular mechanisms are largely unknown. Thus, the third objective of this thesis research was to understand the mechanisms of CsSGR-mediated multiple disease resistances and associated gene regulatory network. One pair of near isogenic lines (NILs) including NIL-R (carrying Cssgr) and NIL-S (carrying CsSGR) was developed for the dm1/cla/psl locus through marker-assisted selection. NIL-R exhibited less severe disease symptoms (chlorosis) than NIL-S in response to inoculation of any of the DM, AR, or ALS pathogen. The expression of CsSGR and another critical chlorophyll catabolic gene CsPPH was less up-regulated in NIL-R than in NIL-S upon inoculation of DM, AR, ALS pathogens. In NIL-S, pathogen infection caused more cell death and accumulation of hydrogen peroxide than in NIL-R. Transcriptome profiling with RNA-Seq identified differentially expressed genes (DEGs) between the NILs in response to pathogen inoculation including down-regulated genes in NIL-R which were enriched into the Gene Ontology (GO) terms of detoxification of hydrogen peroxide and leaf senescence and up-regulated genes in NIL-R were enriched into the GO terms of chlorophyll biosynthesis and assembly of photosystem- light harvesting complex. Transcriptome analysis of NIL-R and S prior to pathogen infection reveals that down-regulated DEGs in NIL-R were enriched into photosynthesis and chloroplast associated GO terms. Yeast two hybrid and BiFC assays identified physical interaction between CsSGR and CsLhcb1, which seemed to be impaired between the mutant type Cssgr with CsLhcb1. NIL-R also displayed 'stay-green' post infection of PM and TLS in addition to DM, AR, and ALS and provided moderate resistance to DM in open fields, suggesting that STAYGREEN (SGR) is a promising genetic resource for providing durable and broad-spectrum disease resistance in crops. Three major-effect QTL for DM resistance including dm4.1 and dm5.2, which were shared by WI7120 and WI7088D, and dm5.3 from WI7088D were successfully pyramided into Gy14, and 9930 backgrounds. Introgression lines with different combinations of three QTL were obtained. Those pyramiding lines provided effective resistance against DM pathogens both in controlled environments and open fields. Though the mean DM score of the Q3-dm4.1+dm5.2+dm5.3 pyramiding line was not significantly different from various Q2 pyramiding lines either in 9930 or Gy14 background. Additionally, their fruit size traits were also evaluated in field trials. Additional DM screening tests and horticultural traits evaluation will be needed to assess their potential values in commercial cucumber breeding.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798834033431Subjects--Topical Terms:

555447
Horticulture.
Subjects--Index Terms:

Downy mildewIndex Terms--Genre/Form:

542853
Electronic books.

Genetic Mapping of Downy and Powdery Mildew Resistances and Characterization of CsSGR-Dependent Broad-Spectrum Disease Resistance in Cucumber (Cucumis sativus L.).
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520 $a Downy mildew (DM) caused by the oomycete pathogen Pseudoperonospora cubensis is an important disease of cucumber and other cucurbits. The effective protection conferred by a recessive resistance locus dm1 originated from the Indian germplasm line PI 197087 lasted for more than 50 years until the new stain(s) emerged in 2004. So far, control of DM in the field relies mainly on the application of fungicides. Some studies reveal that P. cubensis is a pathogenic organism that is prone to develop fungicide resistance. It is important to develop cucumber lines providing more effective and durable resistance to the dynamic pathogen populations in the field. Previous studies identified multiple quantitative traits loci (QTL) for DM resistance in the cucumber inbred line WI7088D (a selection from PI 197088) including the major-effect QTL dm5.3 on cucumber chromosome 5. Therefore, the first of objective in this thesis research was to fine map dm5.3. A BC4F2:3 NIL segregating population for dm5.3 was developed in the 9930 (susceptible) genetic background, which was genotyped using 21 SNPs, Indels, and SSR markers and phenotyped for their responses to DM inoculations under multiple environments. The dm5.3 locus was eventually narrowed into a 144kb region with 12 annotated genes. The analysis of allelic diversity and gene expression patterns supported CsGy5G027140 as the most likely candidate gene for dm5.3, which encodes a sigma factor binding protein (CsSIB1). Powdery mildew (PM) caused by the ascomycete fungal pathogen Podosphaera xanthii is one of the important diseases of cucumber and other cucurbits. A previous study identified four quantitative traits loci (QTL) for PM resistance WI7088D including the major-effect QTL pm5.3 co-localized with major-effect DM resistance QTL dm5.3, but their relationship is unknown. Thus, the second objective of this thesis project was to identify the candidate gene for pm5.3. Fine genetic mapping using the same NIL-derived segregating population for dm5.3 delimited the pm5.3 locus into a 211kb region with 27 annotated genes. CsGy5G026660, that encodes an MLO-like protein, is a possible candidate for pm5.3. Downy mildew (DM), anthracnose (AR), and angular leaf spot (ALS) are three major cucumber diseases. Previous studies found that a loss-of-function mutation inside the cucumber STAYGREEN (CsSGR) gene underlying the dm1/cla/psl locus confers broad-spectrum and durable resistances against three pathogens with different life styles. However, the molecular mechanisms are largely unknown. Thus, the third objective of this thesis research was to understand the mechanisms of CsSGR-mediated multiple disease resistances and associated gene regulatory network. One pair of near isogenic lines (NILs) including NIL-R (carrying Cssgr) and NIL-S (carrying CsSGR) was developed for the dm1/cla/psl locus through marker-assisted selection. NIL-R exhibited less severe disease symptoms (chlorosis) than NIL-S in response to inoculation of any of the DM, AR, or ALS pathogen. The expression of CsSGR and another critical chlorophyll catabolic gene CsPPH was less up-regulated in NIL-R than in NIL-S upon inoculation of DM, AR, ALS pathogens. In NIL-S, pathogen infection caused more cell death and accumulation of hydrogen peroxide than in NIL-R. Transcriptome profiling with RNA-Seq identified differentially expressed genes (DEGs) between the NILs in response to pathogen inoculation including down-regulated genes in NIL-R which were enriched into the Gene Ontology (GO) terms of detoxification of hydrogen peroxide and leaf senescence and up-regulated genes in NIL-R were enriched into the GO terms of chlorophyll biosynthesis and assembly of photosystem- light harvesting complex. Transcriptome analysis of NIL-R and S prior to pathogen infection reveals that down-regulated DEGs in NIL-R were enriched into photosynthesis and chloroplast associated GO terms. Yeast two hybrid and BiFC assays identified physical interaction between CsSGR and CsLhcb1, which seemed to be impaired between the mutant type Cssgr with CsLhcb1. NIL-R also displayed 'stay-green' post infection of PM and TLS in addition to DM, AR, and ALS and provided moderate resistance to DM in open fields, suggesting that STAYGREEN (SGR) is a promising genetic resource for providing durable and broad-spectrum disease resistance in crops. Three major-effect QTL for DM resistance including dm4.1 and dm5.2, which were shared by WI7120 and WI7088D, and dm5.3 from WI7088D were successfully pyramided into Gy14, and 9930 backgrounds. Introgression lines with different combinations of three QTL were obtained. Those pyramiding lines provided effective resistance against DM pathogens both in controlled environments and open fields. Though the mean DM score of the Q3-dm4.1+dm5.2+dm5.3 pyramiding line was not significantly different from various Q2 pyramiding lines either in 9930 or Gy14 background. Additionally, their fruit size traits were also evaluated in field trials. Additional DM screening tests and horticultural traits evaluation will be needed to assess their potential values in commercial cucumber breeding.
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