A New Grape Downy Mildew Resistance Gene for the Wine Industry

Scientists at Cornell University have unearthed a novel gene conferring resistance to grape downy mildew, providing the wine and grape industry with a potent weapon to combat its destructive power.

“Of the downy mildew resistance genes found in the world to date, this is one of the strongest. The discovery could help breeders develop more resistant grape varieties,” stated Lance Cadle-Davidson, Adjunct Professor in the School of Integrative Plant Science in the College of Agriculture and Life Sciences, and a Research Plant Pathologist with the USDA’s Grape Genetics Research Unit in Geneva.

Grape downy mildew (GDM), attributed to the fungus Plasmopara viticola, stands as one of the most detrimental grape afflictions in the Eastern United States.

Grape clusters become exceptionally vulnerable once the vines complete their flowering stage, and infections that occur late in the season can lead to the defoliation of vines just as the berries are in the process of ripening. This adversely affects maturation, winter resilience, and ultimately, crop yield.

The research was published in the journal Plant Physiology on September 14^th, 2023.

The lead authors of the study were Cheng Zou, a research associate at Cornell’s Bioinformatics Facility, Qi Sun, Co-Director of the Facility, Surya Sapkota, a Former Postdoctoral Researcher and now grape breeder at the USDA and Cadle-Davidson.

The gene was unearthed within a grapevine variety known as Vitis x doaniana, a naturally occurring hybrid originating from two wild grapevines. This accession is presently conserved within the USDA-ARS grape germplasm repository situated at Cornell AgriTech.

Cadle-Davidson observed that this particular accession exhibited resistance to downy mildew in the field and sought assistance from the Bioinformatics Facility for further exploration.

Utilizing a streamlined three-step process, as developed by the VitisGen2 project, a collaborative effort aimed at reducing the time, labor, and expenses associated with advancing the next generation of grape varieties, the facility successfully pinpointed the responsible gene within a mere two-month timeframe.

Employing low-resolution genetic mapping within a sizeable breeding population, the team initially reduced the pool of potential gene candidates to a few hundred. Subsequently, through high-resolution mapping of the recombinants, the list of gene candidates was further refined to a mere couple of dozen.

Ultimately, by employing a phased assembly of the Vitis x doaniana parent chromosomes and conducting a comparative analysis of the resistant and susceptible alleles, the precise genetic underpinnings of downy mildew resistance were successfully pinpointed.

One of the most groundbreaking components of this research is the strategy that was used because it could be a gamechanger for specialty crop breeders everywhere. Breeders could use this process to quickly and efficiently identify genes in other heterozygous crops such as apples.”

Qi Sun, Co-Director of the Facility, Cornell University

In the event of creating new grape varieties, the recently uncovered gene has the potential to assist growers in combating grape downy mildew (GDM) over the long haul. This is especially crucial as climate change triggers an increase in GDM outbreaks throughout the Northeast.

Growers commonly use fungicides to control GDM, but GDM can eventually build up resistance to fungicides. Developing new grape varieties for growers with a variety of strong resistant genes is the ultimate solution.”

Bruce Reisch, Grape Breeder, Professor Emeritus, Horticulture, CALS

In the Northeast, a standard vinifera vineyard often necessitates more than a dozen applications of fungicides to combat downy mildew, powdery mildew, and other diseases.

If a grower were to produce grapes that had resistance to these diseases, the number of sprays in a vineyard could potentially go down to one to two per year. With the tools we have now, there are endless possibilities to develop new grapes that deliver on both quality and disease resistance.”

Bruce Reisch, Grape Breeder, Professor Emeritus, Horticulture, CALS