Polyclonal selection in ancient grapevine varieties: genetic gains and stability across environments

Abstract

Conserving and exploiting intra-varietal diversity in ancient grapevine varieties is essential to secure their future use whilst preserving the genetic heritage of historical winegrowing regions. Two complementary strategies are recommended: (i) conserving representative samples of intra-varietal variability to safeguard genetic resources; and (ii) deploying that variability through polyclonal selection to enhance and promote the cultivation of each variety. In Portugal, this approach includes the conservation of more than 50,000 accessions from over 300 Portuguese varieties by PORVID, together with their utilisation in polyclonal selection schemes. By maintaining heterogeneous plant material—often from rarely cultivated varieties with underexplored potential—and by implementing polyclonal selection, this approach enhances viticultural sustainability, responds to evolving producer and consumer requirements, and improves adaptation to climate change, whilst supporting stable varietal performance across environments.

This study aims to (1) formulate a theoretical framework for genetic gains in polyclonal selection and (2) demonstrate the flexibility of selection criteria, the precision of predicted genetic gains, and the stability of selected polyclonal material across environments. Multi-environment field trials of ancient grapevine varieties were established using resolvable row– column experimental designs and were phenotyped for agronomically and economically relevant traits, including yield, must quality parameters. Linear mixed models were fitted to predict selection gains under alternative criteria. Stability across environments was evaluated using prediction intervals for genetic gains. The flexibility of defining selection targets and optimising gains was further illustrated using the R package maxRgain: Maximising Polyclonal Selection Gains Using Integer Programming.

Overall, the results show that polyclonal selection enables accurate and precise prediction of genetic gains and promotes stability across environments. These findings support polyclonal selection as an effective breeding and conservation- oriented strategy to valorise intra-varietal variability in autochthonous grapevine germplasm and to strengthen the resilience of viticulture under current and future challenges.

Acknowledgements

The authors thank their colleagues for their dedication and support in selecting polyclonal material. This research was funded by the projects “Save the intra-varietal diversity of autochthonous grapevine varieties” (PRR-C05-i03-000016) and “BioGrapeSustain” (C644866286-011, PRR – Agendas Mobilizadoras, B6.1).