Intravarietal diversity: an opportunity for climate change adaptation
Abstract
Abstract:
Context and purpose of the study
Merlot grapevine is the second wine cultivar most planted in the world and especially in the Bordeaux wine region.
This cultivar has many advantages in producing high quality wine; however, in the last decade, climate change has
increased the sugar concentration in berries at harvest and shortened the maturation cycle. If this has been up to
now a great opportunity to improve wine quality profile, we are touching the tipping point. High sugar
concentration at harvest induces high alcool content in wine which can negatively impact wine quality. There are
many viticultural and oenological practices possible to limit this effect. In this study we focus on plant material
through intra-varietal diversity of Merlot cultivar.
Material and methods
This study is based on three years of phenotyping a private collection of Merlot including 55 accessions and 3
ENTAV-INRA® registered clones. Each genotype is present in four blocks of 6 vines in the experimental plot. Among
this collection, two extreme genotypes for sugar concentration, selected on 3 years of phenotyping, were
phenotyped again on the fourth year at a larger scale. Separated individual berries were collected at 5 stages from
green hard berries to mature berries. Sugar and organic acids were mearsured on each berry to compare both
maturation cycles and to select triplicates of synchronized individual berries before transcriptomic analysis. Pair
ended RNAseq reads were then aligned on high quality Merlot assembly and the counting table of gene expression
was produced.
Results
Extreme genotypes have an average of 17g.L-1 difference in sugar concentration at harvest which approximately
represents 1%vol of alcool in wine after fermentation. Whilst as expected thousands of genes were differentially
expressed according to the advancement of ripening, statistical analysis only revealed 28 differentially expressed
genes between the two genotypes throughtout all developmental stages and gives an insight on genes potentially
involved in the control of sugar concentration. Selection among intra-varietal diversity therefore appears as a tool
to immediate adaptation but also offers possibilities in gene detection of very specific agronomical traits.