Genotype responses of two apple rootstocks to infection by <i>Pythium ultimum</i> causing apple replant disease

Zhu, Yanmin; Shin, Sungbong; Mazzola, Mark

doi:10.1080/07060661.2016.1260640

Cited by 36 publications

(42 citation statements)

References 27 publications

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“…In the literature, phytoalexins are described to be a part of the induced defense response against biotic stressors, fungi in particular [59]. BIS3 expression was reported previously in apple upon fire blight infection [60] and upon infection with Pythium ultimum, one causal agent of ARD [61,62]. Taking these studies together with further studies from our group [11,32,33,63], the phytoalexin biosynthesis is a clear and highly specific part of the Malus response to ARD.…”

Section: Plos Onementioning

confidence: 55%

Identification and validation of early genetic biomarkers for apple replant disease

et al. 2020

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Apple replant disease (ARD) is a serious threat to producers of apple trees and fruits worldwide. The ARD etiology is not unraveled and managing options are either economically not applicable or environmentally harmful. Thus, interest is given in biomarkers that allow to indicate ARD situations at early time points in order to classify soils according to ARD severity but also to analyze the effectiveness to potential countermeasures. This study aimed at (i) identifying ARD biomarkers on the transcriptional level in root tissue by analyzing the expression of previously identified candidate genes in ARD soils of different origin and texture and (ii) testing the specificity of these marker genes to ARD. In vitro propagated M26 plantlets were submitted to a bio-test with three ARD soils, either untreated or disinfected by γ-irradiation. Expression of seven candidate genes identified in a previous transcriptomic study was investigated by RT-qPCR in a time course experiment. Already three days after planting, a prominent upregulation of the phytoalexin biosynthesis genes biphenyl synthase 3 (BIS3) and biphenyl 4-hydroxylase (B4Hb) was observed in the untreated ARD variants of all three soils. The phytoalexin composition in roots was comparable for all three soils and the total phytoalexin content correlated with the expression of BIS3 and B4Hb. The third promising candidate gene that was upregulated under ARD conditions was the ethyleneresponsive transcription factor 1B-like (ERF1B). In a second experiment M26 plantlets were exposed to different abiotic stressors, namely heat, salt and nutrient starvation, and candidate gene expression was determined in the roots. The expression levels of BIS3 and B4Hb were highly and specifically upregulated in ARD soil, but not upon the abiotic stress conditions, whereas ERF1B also showed higher expression under heat stress. In conclusion, BIS3 and B4Hb are recommended as early ARD biomarkers due to their high expression levels and their high specificity.

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Section: Plos Onementioning

confidence: 55%

Identification and validation of early genetic biomarkers for apple replant disease

et al. 2020

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“…Previously, contrasting resistance phenotypes were demonstrated to exist between these two cultivars when they were challenged by the soilborne pathogen of P. ultimum [11]. Interestingly, the current data set indicated that a preformed defense system exists in the root tissues of resistant cultivar G.935, but not susceptible B.9.…”

Section: Discussionmentioning

confidence: 61%

Comparative Transcriptome Analysis Reveals a Preformed Defense System in Apple Root of a Resistant Genotype of G.935 in the Absence of Pathogen

Zhu

Shao²,

Zhou

et al. 2017

International Journal of Plant Genomics

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Two apple rootstock genotypes G.935 and B.9 were recently demonstrated to exhibit distinct resistance responses following infection by Pythium ultimum. As part of an effort to elucidate the genetic regulation of apple root resistance to soilborne pathogens, preinoculation transcriptome variations in roots of these two apple rootstock genotypes are hypothesized to contribute to the observed disease resistance phenotypes. Results from current comparative transcriptome analysis demonstrated elevated transcript abundance for many genes which function in a system-wide defense response in the root tissue of the resistant genotype of G.935 in comparison with susceptible B.9. Based on the functional annotation, these differentially expressed genes encode proteins that function in several tiers of defense responses, such as pattern recognition receptors for pathogen detection and subsequent signal transduction, defense hormone biosynthesis and signaling, transcription factors with known roles in defense activation, enzymes of secondary metabolism, and various classes of resistance proteins. The data set suggested a more poised status, which is ready to defend pathogen infection, in the root tissues of resistant genotype of G.935, compared to the susceptible B.9. The significance of preformed defense in the absence of a pathogen toward overall resistance phenotypes in apple root and the potential fitness cost due to the overactivated defense system were discussed.

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“…This corresponds well with the findings, that parasitic fungi and oomycetes of the genera Cylindrocarpon (Tewoldemedhin et al, 2011b;Mazzola and Manici, 2012;Franke-Whittle et al, 2015;Manici et al, 2015), Phytophthora (Tewoldemedhin et al, 2011a;Mazzola and Manici, 2012), Pythium (Tewoldemedhin et al, 2011a;Mazzola and Manici, 2012;Manici et al, 2013), and Rhizoctonia (Tewoldemedhin et al, 2011a;Mazzola and Manici, 2012;Manici et al, 2013) are enriched in ARD soil in comparison to healthy or disinfected soil. In particular, genes of the biphenyl biosynthetic pathway were rapidly activated in the roots of apple plants grown in ARD soil (Zhu et al, 2014;Zhu et al, 2016;Weiß et al, 2017a;Weiß et al, 2017b). Phytoalexins like biphenyls and dibenzofurans are known to act in an induced defense mechanism against biotic stressors, such as fungi and bacteria (Ahuja et al, 2012;Chizzali et al, 2012b;Chizzali and Beerhues, 2012;Chizzali et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

“…Phytoalexins like biphenyls and dibenzofurans are known to act in an induced defense mechanism against biotic stressors, such as fungi and bacteria (Ahuja et al, 2012;Chizzali et al, 2012b;Chizzali and Beerhues, 2012;Chizzali et al, 2013). Interestingly, the activation of phytoalexin biosynthesis genes was also found when the plants were inoculated with Pythium ultimum, one component of the ARD complex (Shin et al, 2016b;Zhu et al, 2016). Along with the elevated gene expression, individual phytoalexin compounds were found in higher abundances in roots growing in ARD soils (Weiß et al, 2017b).…”

Section: Introductionmentioning

confidence: 99%

Genes Involved in Stress Response and Especially in Phytoalexin Biosynthesis Are Upregulated in Four Malus Genotypes in Response to Apple Replant Disease

et al. 2020

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Apple replant disease (ARD) is a soil-borne disease, which is of particular importance for fruit tree nurseries and fruit growers. The disease manifests by a poor vegetative development, stunted growth, and reduced yield in terms of quantity and quality, if apple plants (usually rootstocks) are replanted several times at the same site. Genotypespecific differences in the reaction of apple plants to ARD are documented, but less is known about the genetic mechanisms behind this symptomatology. Recent transcriptome analyses resulted in a number of candidate genes possibly involved in the plant response. In the present study, the expression of 108 selected candidate genes was investigated in root and leaf tissue of four different apple genotypes grown in untreated ARD soil and ARD soil disinfected by g-irradiation originating from two different sites in Germany. Thirty-nine out of the 108 candidate genes were differentially expressed in roots by taking a p-value of < 0.05 and a fold change of > 1.5 as cutoff. Sixteen genes were more than 4.5-fold upregulated in roots of plants grown in ARD soil. The four genes MNL2 (putative mannosidase); ALF5 (multi antimicrobial extrusion protein); UGT73B4 (uridine diphosphate (UDP)-glycosyltransferase 73B4), and ECHI (chitinbinding) were significantly upregulated in roots. These genes seem to be related to the host plant response to ARD, although they have never been described in this context before. Six of the highly upregulated genes belong to the phytoalexin biosynthesis pathway. Their genotype-specific gene expression pattern was consistent with the phytoalexin content measured in roots. The biphenyl synthase (BIS) genes were found to be useful as early biomarkers for ARD, because their expression pattern correlated well with the phenotypic reaction of the Malus genotypes investigated.

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Genotype responses of two apple rootstocks to infection by Pythium ultimum causing apple replant disease

Cited by 36 publications

References 27 publications

Identification and validation of early genetic biomarkers for apple replant disease

Identification and validation of early genetic biomarkers for apple replant disease

Comparative Transcriptome Analysis Reveals a Preformed Defense System in Apple Root of a Resistant Genotype of G.935 in the Absence of Pathogen

Genes Involved in Stress Response and Especially in Phytoalexin Biosynthesis Are Upregulated in Four Malus Genotypes in Response to Apple Replant Disease

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