Phenotyping bud break and trafficking of dormant buds from grafted vine

Abstract

In grapevine, phenology from bud break to berry maturation, depends on temperature and water availability. Increases in average temperatures accelerates initiation of bud break, exposing newly formed shoots to detrimental environmental stresses. It is therefore essential to identify genotypes that could delay phenology in order to adapt to the environment. The use of different rootstocks has been applied to change scion’s characteristics, to adapt and resist to abiotic and biotic stresses^[1]. It is the main objective of this project to identify rootstock genotypes that could contribute in delaying bud burst in order to adapt to extreme climate events. For this, first we investigated the cold requirements to achieve a homogenous bud break pattern from cuttings of Merlot, Cabernet Sauvignon and Chasselas^[2]. Interestingly, Merlot needs longer cold exposure times to achieve 100% bud break. Moreover, bud break of different Vitis species was assessed in the field. Two late and one early Vitis were identified which will be used as rootstock in grafts with Cabernet Sauvignon. Bud break times of these combinations will be assessed to identify changes in bud dormancy in the scion. Furthermore, buds from Cabernet Sauvignon, Merlot and RGM are being sampled for a year-cycle to follow bud development, dormancy and bud break by RNAseq and metabolomics. This, coupled with QTLs identified from bud break of a population of Cabernet Sauvignon x Vitis riparia, will allow the identification of genes involved in dormancy and bud break. Lastly, to understand the rootstock/scion/bud communication, traficking of calceine in cuttings containing dormant and non-dormant buds was studied to indicate the moment in which this molecule is able to enter the bud. Results show that calceine is not able to enter the bud in either condition therefore, 32P is being used to rule out a possible molecular size effect.

Acknowledgements: We thank Lysiane Brocard from the Bordeaux Imaging Center for the advice on microscopy and Bordeaux Plant Sciences from the Université de Bordeaux for funding this research through the Grand Programme de Recherche (GPR).

1)  Miele A. (2019). Rootstock-scion interaction:6. Phenology, chilling and heat requirements of Cabernet Sauvignon grapevine. Revista Brasileira de Fruticultura 41.