Evaluation of budbreak regulation on grapevine genotypes with extreme behaviour

Abstract

Vitis vinifera enters dormancy in autumn to face adverse winter conditions and, then, resumes growth and budbreak (BB) in spring, when optimal climate conditions occur.

Climate change can cause yield damage due to phenology advances and spring frosts. Genes and pathways involved in dormancy and BB progression were previously enquired in grape, but an extensive understanding of the whole regulatory network is still lacking.

Here, we focused on a segregating population that was evaluated in the field for 6 years for phenological traits. BB timing in the parents was similar, whereas in the progeny it spanned a long interval (71 days in 2025). The transgressive behaviour was strongly correlated across replicates and across years, and individuals consistently breaking earlier or later than the parents were identified.

Based on BB timing data, few individuals showing opposite behaviour (3 early and 2 late BB timing genotypes) where chosen, along with the parents, for further phenotypic characterization. BB forcing assay (BFA) was performed over winter to test dormancy progression. Cold hardiness (CH) was also evaluated with differential thermal analysis (DTA). For these analyses, samples were collected every 3 weeks from November to March over two years. Moreover, the dynamic development of grapevine buds under natural field conditions was monitored over BB by microscopy observation of vascular connection rebuild progression in the different genotypes. Based on BFA all genotypes already exited endodormancy in January with no obvious differences between early and late ones. The different CH and cold de-acclimation behaviours in the genotypes appeared also not clearly correlated to the extreme field BB behaviours.

Altogether, the physiological characterization will provide useful insights in dissecting the extreme BB phenotype, paving the way for future studies on the underlying molecular mechanisms.