Grapevines are severely affected by downy mildew, which leads to substantial crop losses. While chemical fungicides are commonly used for control, they are increasingly criticized for their environmental impact and resistance issues. Grapevine breeding programs have traditionally focused on introducing resistance from wild species. However, Georgian grapevine varieties, including Mgaloblishvili, offer a promising alternative source of natural resistance. Previous studies have highlighted Mgaloblishvili’s effective defense against P. viticola, but the genetic basis of this resistance remained unclear. Based on these challenges, further investigation into the genetic mechanisms underlying this resistance is crucial for advancing sustainable grapevine breeding strategies.
A team of researchers led by Valentina Ricciardi from the University of Milan, in collaboration with several international institutions, has mapped the genome of Vitis vinifera cv. Mgaloblishvili, identifying critical loci responsible for its resistance to downy mildew. Published (DOI: 10.1093/hr/uhaf055) in Horticulture Research on February 20, 2025, the study provides valuable genomic insights into how this grape variety defends itself against one of the most destructive pathogens in viticulture.
Using PacBio HiFi sequencing technology, researchers generated a high-quality chromosome-scale diploid genome for Mgaloblishvili, encompassing 986 Mbp of DNA and 58,912 predicted protein-coding genes. This genome was compared to the genome of the susceptible grapevine variety PN40024 to identify structural variants (SVs) and SNPs that distinguish the resistant variety. Key findings include the identification of three resistance loci: Rpv29 on chromosome 14, Rpv30 on chromosome 3, and Rpv31 on chromosome 16. These loci were found to be enriched with genes involved in plant defense pathways. For instance, the Rpv29 locus exhibited reduced gene content compared to PN40024, while Rpv31 displayed similar gene content but with differential regulation. The Rpv30 locus posed challenges due to its complex structure and repetitive sequences. Through DNA sequencing of self-pollinated progeny, the team identified specific resistance haplotypes, revealing that Mgaloblishvili’s resistance is partly due to small SVs and SNPs that alter gene expression and disrupt susceptibility factors.
“This study represents a significant breakthrough in understanding the genetic basis of downy mildew resistance in grapevines,” said Dr. Dario Cantu, a co-author and expert in viticulture and genomics at the University of California Davis. “By dissecting the resistance loci in Mgaloblishvili, we not only gain insight into the genetic factors that drive this resistance but also open new pathways for breeding grapevines with improved disease resistance, crucial for sustainable viticulture practices.”
The discovery of these resistance loci provides an invaluable resource for grapevine breeding programs aiming to develop varieties with durable resistance to downy mildew. The study’s findings could lead to more efficient breeding strategies by targeting specific genetic loci that confer resistance, minimizing the need for chemical pesticides. Additionally, understanding the genetic underpinnings of Mgaloblishvili’s defense mechanisms could have broader implications for other crops facing similar pathogen pressures. Future research could explore the potential for stacking these resistance loci in elite cultivars, providing long-term solutions to managing downy mildew in grape production.
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References
DOI
10.1093/hr/uhaf055
Original Source URL
https://doi.org/10.1093/hr/uhaf055
Funding information
This work was partially supported by the USDA NIFA Award #2022-51181-38240 and ‘Grape for vine: recycling grape wastes to protect grapevine from fungal pathogens (Grape4vine)’ project financed by Fondazione Cariplo (Ref. 2022-0617). The Authors thank the Agriculture, Environment, and Bioenergy Doctorate programme of the University of Milan. The authors acknowledge support from the University of Milan through the APC initiative.
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.