Gene Deletions Cause Grapevine Resistance to Downy Mildew to Fail

Greg Howard
18th July, 2024

Gene Deletions Cause Grapevine Resistance to Downy Mildew to Fail

Image Source: Natural Science News, 2024

Key Findings

  • The study focused on grapevine downy mildew caused by Plasmopara viticola and its impact on grapevine resistance
  • Researchers identified a genomic region, avrRpv3.1, linked to the breakdown of grapevine resistance
  • Structural variations, including deletions in the avrRpv3.1 locus, were found in virulent P. viticola strains, explaining their ability to overcome resistance
Grapevine downy mildew, caused by the oomycete Plasmopara viticola, poses a significant threat to the global cultivation of Eurasian wine grapes, Vitis vinifera. Although resistant grapevine varieties are becoming more accessible, P. viticola populations are rapidly evolving to overcome these resistances. A recent study conducted by INRAE aimed to uncover avirulence genes related to Rpv3.1-mediated grapevine resistance[1]. The research team sequenced the genomes and characterized the development of 136 P. viticola strains on both resistant and sensitive grapevine cultivars. Through a genome-wide association study, they identified genomic variations linked to resistance-breaking phenotypes. They discovered a genomic region associated with the breakdown of Rpv3.1 grapevine resistance, referred to as the avrRpv3.1 locus. A detailed reassembly of the P. viticola INRA-Pv221 genome revealed structural variations in this locus, including a 30 kbp deletion. Virulent P. viticola strains exhibited multiple deletions on both haplotypes at the avrRpv3.1 locus. These deletions involved two paralog genes coding for proteins with 800-900 amino acids and signal peptides. These proteins displayed a structure featuring LWY-fold structural modules, which are common among oomycete effectors. When these proteins were transiently expressed, they induced cell death in grapevines carrying Rpv3.1 resistance, confirming their avirulence nature. This discovery provides insight into the genetic mechanisms enabling P. viticola to adapt to grapevine resistance, laying a foundation for developing strategies to manage this destructive crop pathogen. The findings build upon previous studies that have explored the genetic and molecular underpinnings of downy mildew resistance in grapevines. For instance, earlier research identified the Rpv3 locus on chromosome 18 of grapevines, which is responsible for the onset of a hypersensitive response (HR) at infection sites[2]. This HR response is a crucial defense mechanism that limits pathogen growth and reduces disease symptoms. The current study's identification of the avrRpv3.1 locus and its associated structural variations further elucidates how P. viticola can overcome this resistance. Additionally, the study's findings align with previous research on the molecular mechanisms of resistance in P. viticola. For example, a study on carboxylic acid amide (CAA) fungicide resistance in P. viticola identified a single nucleotide polymorphism (SNP) in the PvCesA3 gene that conferred resistance to the fungicide[3]. This underscores the importance of understanding the genetic basis of pathogen resistance to develop effective management strategies. The identification of the avrRpv3.1 locus and its associated structural variations provides a critical piece of the puzzle in understanding how P. viticola adapts to grapevine resistance. By revealing the genetic mechanisms that enable the pathogen to overcome Rpv3.1-mediated resistance, this study offers valuable insights that could inform the development of new strategies to manage grapevine downy mildew. This research highlights the importance of continued genomic studies to stay ahead of rapidly evolving pathogens and protect vital agricultural crops.

GeneticsBiochemPlant Science

References

Main Study

1) Multiple deletions of candidate effector genes lead to the breakdown of partial grapevine resistance to downy mildew.

Published 18th July, 2024

https://doi.org/10.1111/nph.19861

Related Studies

2) Resistance to Plasmopara viticola in grapevine 'Bianca' is controlled by a major dominant gene causing localised necrosis at the infection site.

https://doi.org/10.1007/s00122-009-1167-2

3) A single point mutation in the novel PvCesA3 gene confers resistance to the carboxylic acid amide fungicide mandipropamid in Plasmopara viticola.

https://doi.org/10.1016/j.fgb.2010.02.009


Related Articles

An unhandled error has occurred. Reload 🗙