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Current understanding of grapevine defense mechanisms against the biotrophic fungus (Erysiphe necator), the causal agent of powdery mildew disease.

Qiu W, Feechan A, Dry I - Hortic Res (2015)

Bottom Line: The majority of grapevine cultivars used for wine, table grape, and dried fruit production are derived from the Eurasian grape species Vitis vinifera because of its superior aroma and flavor characteristics.The integration of effective genetic resistance into cultivated grapevines would lead to significant financial and environmental benefits and represents a major challenge for viticultural industries and researchers worldwide.Finally, it addresses future research priorities which will be important in the rapid identification, evaluation, and deployment of new PM resistance genes which are capable of conferring effective and durable resistance in the vineyard.

View Article: PubMed Central - PubMed

Affiliation: Center for Grapevine Biotechnology, W. H. Darr School of Agriculture, Missouri State University , Mountain Grove, MO 65711, USA.

ABSTRACT
The most economically important disease of cultivated grapevines worldwide is powdery mildew (PM) caused by the ascomycete fungus Erysiphe necator. The majority of grapevine cultivars used for wine, table grape, and dried fruit production are derived from the Eurasian grape species Vitis vinifera because of its superior aroma and flavor characteristics. However, this species has little genetic resistance against E. necator meaning that grape production is highly dependent on the frequent use of fungicides. The integration of effective genetic resistance into cultivated grapevines would lead to significant financial and environmental benefits and represents a major challenge for viticultural industries and researchers worldwide. This review will outline the strategies being used to increase our understanding of the molecular basis of V. vinifera susceptibility to this fungal pathogen. It will summarize our current knowledge of different resistance loci/genes that have evolved in wild grapevine species to restrict PM infection and assess the potential application of these defense genes in the generation of PM-resistant grapevine germplasm. Finally, it addresses future research priorities which will be important in the rapid identification, evaluation, and deployment of new PM resistance genes which are capable of conferring effective and durable resistance in the vineyard.

No MeSH data available.


Related in: MedlinePlus

Use of the Arabidopsis pen1 mutant for rapid screening of candidate grapevine powdery mildew resistance genes. The pen1-1 mutant line that allows increased penetration of non-adapted powdery mildew species was transformed with the grapevine powdery mildew resistance gene MrRUN1 and inoculated with either grapevine powdery mildew (E. necator) or Arabidopsis powdery mildew (E. cichoracearum). Programmed cell death (PCD) was estimated by trypan blue staining of inoculated leaves at 2 dpi. Each data point is the mean of three independent experiments (±standard deviation). In each experiment, a minimum of 100 germinated conidia were scored on each of three leaves for each line. Asterisk indicates a statistically significant difference from pen1-1 (P < 0.05; Student's t-test).
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fig2: Use of the Arabidopsis pen1 mutant for rapid screening of candidate grapevine powdery mildew resistance genes. The pen1-1 mutant line that allows increased penetration of non-adapted powdery mildew species was transformed with the grapevine powdery mildew resistance gene MrRUN1 and inoculated with either grapevine powdery mildew (E. necator) or Arabidopsis powdery mildew (E. cichoracearum). Programmed cell death (PCD) was estimated by trypan blue staining of inoculated leaves at 2 dpi. Each data point is the mean of three independent experiments (±standard deviation). In each experiment, a minimum of 100 germinated conidia were scored on each of three leaves for each line. Asterisk indicates a statistically significant difference from pen1-1 (P < 0.05; Student's t-test).

Mentions: With the identification of an increasing number of R-gene candidates, it will be essential that techniques are available to functionally characterize these genes. Ideally, this would involve stable transformation of a susceptible V. vinifera cultivar with the R-gene candidates to challenge them with a range of E. necator isolates32. However, R-loci typically contain multiple R-gene candidates and stable grapevine transformation, despite technical improvements69, remains a long and technically challenging process. Alternative strategies are needed to facilitate rapid evaluation of these R-gene candidates. One possibility is the use of transient expression systems such as agroinoculation70. This approach has been used to demonstrate the anti-fungal activity of VpPR10.1 against E. necator71 (Table 2). It might also be feasible to test grapevine R-gene function by transforming into Arabidopsis mutants in which PTI has been compromised allowing E. necator to penetrate and form haustoria72. Figure 2 shows the results of an experiment in which the PM resistance gene MrRUN1, was transformed into the Arabidopsis pen1-1 mutant. Inoculation of these pen1-1 mutants with E. necator resulted in a significant induction of PCD in transgenic lines containing MrRUN1 but not in the pen1-1 control lines32. Furthermore, MrRUN1-mediated PCD in Arabidopsis was only induced in response to penetration by E. necator and not observed with E. cichoracearum demonstrating the response is specific to grapevine PM. Thus, this approach could be used to rapidly evaluate multiple R-gene candidates before selected genes are introduced into susceptible V. vinifera cultivars for final validation.


Current understanding of grapevine defense mechanisms against the biotrophic fungus (Erysiphe necator), the causal agent of powdery mildew disease.

Qiu W, Feechan A, Dry I - Hortic Res (2015)

Use of the Arabidopsis pen1 mutant for rapid screening of candidate grapevine powdery mildew resistance genes. The pen1-1 mutant line that allows increased penetration of non-adapted powdery mildew species was transformed with the grapevine powdery mildew resistance gene MrRUN1 and inoculated with either grapevine powdery mildew (E. necator) or Arabidopsis powdery mildew (E. cichoracearum). Programmed cell death (PCD) was estimated by trypan blue staining of inoculated leaves at 2 dpi. Each data point is the mean of three independent experiments (±standard deviation). In each experiment, a minimum of 100 germinated conidia were scored on each of three leaves for each line. Asterisk indicates a statistically significant difference from pen1-1 (P < 0.05; Student's t-test).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595975&req=5

fig2: Use of the Arabidopsis pen1 mutant for rapid screening of candidate grapevine powdery mildew resistance genes. The pen1-1 mutant line that allows increased penetration of non-adapted powdery mildew species was transformed with the grapevine powdery mildew resistance gene MrRUN1 and inoculated with either grapevine powdery mildew (E. necator) or Arabidopsis powdery mildew (E. cichoracearum). Programmed cell death (PCD) was estimated by trypan blue staining of inoculated leaves at 2 dpi. Each data point is the mean of three independent experiments (±standard deviation). In each experiment, a minimum of 100 germinated conidia were scored on each of three leaves for each line. Asterisk indicates a statistically significant difference from pen1-1 (P < 0.05; Student's t-test).
Mentions: With the identification of an increasing number of R-gene candidates, it will be essential that techniques are available to functionally characterize these genes. Ideally, this would involve stable transformation of a susceptible V. vinifera cultivar with the R-gene candidates to challenge them with a range of E. necator isolates32. However, R-loci typically contain multiple R-gene candidates and stable grapevine transformation, despite technical improvements69, remains a long and technically challenging process. Alternative strategies are needed to facilitate rapid evaluation of these R-gene candidates. One possibility is the use of transient expression systems such as agroinoculation70. This approach has been used to demonstrate the anti-fungal activity of VpPR10.1 against E. necator71 (Table 2). It might also be feasible to test grapevine R-gene function by transforming into Arabidopsis mutants in which PTI has been compromised allowing E. necator to penetrate and form haustoria72. Figure 2 shows the results of an experiment in which the PM resistance gene MrRUN1, was transformed into the Arabidopsis pen1-1 mutant. Inoculation of these pen1-1 mutants with E. necator resulted in a significant induction of PCD in transgenic lines containing MrRUN1 but not in the pen1-1 control lines32. Furthermore, MrRUN1-mediated PCD in Arabidopsis was only induced in response to penetration by E. necator and not observed with E. cichoracearum demonstrating the response is specific to grapevine PM. Thus, this approach could be used to rapidly evaluate multiple R-gene candidates before selected genes are introduced into susceptible V. vinifera cultivars for final validation.

Bottom Line: The majority of grapevine cultivars used for wine, table grape, and dried fruit production are derived from the Eurasian grape species Vitis vinifera because of its superior aroma and flavor characteristics.The integration of effective genetic resistance into cultivated grapevines would lead to significant financial and environmental benefits and represents a major challenge for viticultural industries and researchers worldwide.Finally, it addresses future research priorities which will be important in the rapid identification, evaluation, and deployment of new PM resistance genes which are capable of conferring effective and durable resistance in the vineyard.

View Article: PubMed Central - PubMed

Affiliation: Center for Grapevine Biotechnology, W. H. Darr School of Agriculture, Missouri State University , Mountain Grove, MO 65711, USA.

ABSTRACT
The most economically important disease of cultivated grapevines worldwide is powdery mildew (PM) caused by the ascomycete fungus Erysiphe necator. The majority of grapevine cultivars used for wine, table grape, and dried fruit production are derived from the Eurasian grape species Vitis vinifera because of its superior aroma and flavor characteristics. However, this species has little genetic resistance against E. necator meaning that grape production is highly dependent on the frequent use of fungicides. The integration of effective genetic resistance into cultivated grapevines would lead to significant financial and environmental benefits and represents a major challenge for viticultural industries and researchers worldwide. This review will outline the strategies being used to increase our understanding of the molecular basis of V. vinifera susceptibility to this fungal pathogen. It will summarize our current knowledge of different resistance loci/genes that have evolved in wild grapevine species to restrict PM infection and assess the potential application of these defense genes in the generation of PM-resistant grapevine germplasm. Finally, it addresses future research priorities which will be important in the rapid identification, evaluation, and deployment of new PM resistance genes which are capable of conferring effective and durable resistance in the vineyard.

No MeSH data available.


Related in: MedlinePlus