Grapevine Genetics: Unraveling the shift from dioecious wild types to cultivated hermaphrodites

In the world of viticulture, the transformation from dioecious wild grapevines to hermaphroditic cultivated varieties presents a fascinating narrative of human influence and genetic adaptation. This journey of the grapevine, scientifically known as Vitis, is marked by significant botanical and genetic developments, shaping the modern wine industry.

Wild Grapevines: A Dioecious Beginning

In nature, grapevines exhibit a dioecious reproductive system, meaning that individual plants are distinctly male or female. This is observed across approximately 70 species of wild Vitis. However, a stark contrast is found in cultivated varieties, all of which are hermaphroditic, possessing both male and female flowers on the same plant.

The subspecies of Vitis vinifera, the primary species used in wine production, further illustrates this dichotomy. While the Vitis vinifera L. subsp. sylvestris retains its dioecious nature, its counterpart, Vitis vinifera L. subsp. sativa, is exclusively hermaphroditic.

The Shift to Hermaphroditism in Cultivation

The transition of grapevines from dioecious to hermaphroditic forms is a result of selective cultivation by humans over centuries. In a study led by Dario Cantù at the University of California, the genetic underpinnings of this shift were explored. The research identified two key genes: one responsible for male fertility and the other for suppressing female fertility.

In the broader context of angiosperms, dioecious species are relatively rare, accounting for only about 6% of flowering plants. Many cultivated plants, such as date palms, persimmons, and asparagus, retain their wild dioecious nature. However, in the case of grapevines, domestication led to a reversion to hermaphroditism.

Implications of Hermaphroditism in Viticulture

The practical implications of cultivating hermaphroditic grapevines are significant. If grapevines remained dioecious, both male and female plants would be necessary for fruit production, complicating cultivation. Male vines would occupy space without yielding fruit, and imperfect fertilization could lead to incomplete grape clusters.

The ability of hermaphroditic grapevines to self-pollinate simplifies cultivation and transportation. This practicality is a key reason for their selection by growers over the years.

Genetic Insights and Future Research

The identification of crucial genes in grapevine fertility is a milestone in viticulture research. It simplifies breeding processes, allowing for genetic analysis to filter out non-hermaphroditic individuals. This knowledge has far-reaching implications for developing new grape varieties, enhancing disease resistance, and improving fruit quality.

Dario Cantù's ongoing research at the University of California aims to expand understanding of other genomic aspects related to disease resistance in grapevines. Cesare Intrieri, a renowned professor emeritus at the University of Bologna, highlights the importance of such genomic studies in understanding the influence of genes on traits like sugar content and aroma development.

As the viticulture industry moves toward sustainability and meeting consumer demands, these genetic insights pave the way for a more efficient and environmentally friendly approach to grape cultivation and wine production.