Shoot chloride exclusion and salt tolerance in grapevine is associated with differential ion transporter expression in roots

BACKGROUND: Salt tolerance in grapevine is associated with chloride (Cl-) exclusion from shoots; the rate-limiting step being the passage of Cl- between the root symplast and xylem apoplast. Despite an understanding of the physiological mechanism of Cl- exclusion in grapevine, the molecular identity of membrane proteins that control this process have remained elusive. To elucidate candidate genes likely to control Cl- exclusion, we compared the root transcriptomes of three Vitis spp. with contrasting shoot Cl- exclusion capacities using a custom microarray. RESULTS: When challenged with 50 mM Cl-, transcriptional changes of genotypes 140 Ruggeri (shoot Cl- excluding rootstock), K51-40 (shoot Cl- including rootstock) and Cabernet Sauvignon (intermediate shoot Cl- excluder) differed. The magnitude of salt-induced transcriptional changes in roots correlated with the amount of Cl- accumulated in shoots. Abiotic-stress responsive transcripts (e.g. heat shock proteins) were induced in 140 Ruggeri, respiratory transcripts were repressed in Cabernet Sauvignon, and the expression of hypersensitive response and ROS scavenging transcripts was altered in K51-40. Despite these differences, no obvious Cl- transporters were identified. However, under control conditions where differences in shoot Cl- exclusion between rootstocks were still significant, genes encoding putative ion channels SLAH3, ALMT1 and putative kinases SnRK2.6 and CPKs were differentially expressed between rootstocks, as were members of the NRT1 (NAXT1 and NRT1.4), and CLC families. CONCLUSIONS: These results suggest that transcriptional events contributing to the Cl- exclusion mechanism in grapevine are not stress-inducible, but constitutively different between contrasting varieties. We have identified individual genes from large families known to have members with roles in anion transport in other plants, as likely candidates for controlling anion homeostasis and Cl- exclusion in Vitis species. We propose these genes as priority candidates for functional characterisation to determine their role in chloride transport in grapevine and other plants.Sam W Henderson, Ute Baumann, Deidre H Blackmore, Amanda R Walker, Rob R Walker and Matthew Gilliha

Genetic and Genomic Approaches for Adaptation of Grapevine to Climate Change

The necessity to adapt to climate change is even stronger for grapevine than for other crops, because grape berry composition—a key determinant of fruit and wine quality, typicity and market value— highly depends on “terroir” (complete natural environment), on vintage (annual climate variability), and on their interactions. In the same time, there is a strong demand to reduce the use of pesticides. Thus, the equation that breeders and grape growers must solve has three entries that cannot be dissociated: adaptation to climate change, reduction of pesticides, and maintenance of wine typicity. Although vineyard management may cope to some extent to the short–medium-term effects of climate change, genetic improvement is necessary to provide long-term sustainable solutions to these problems. Most vineyards over the world are planted using vines that harbor two grafted plants’ genomes. Although this makes the range of interactions (scion-atmosphere, rootstock-soil, scion-rootstock) more complex, it also opens up wider possibilities for the genetic improvement of either or both the grafted genotypes. Positive aspects related to grapevine breeding are as follows: (a) a wide genetic diversity of rootstocks and scions that has not been thoroughly explored yet; (b) progress in sequencing technologies that allows high-throughput sequencing of entire genomes, faster mapping of targeted traits and easier determination of genetic relationships; (c) progress in new breeding technologies that potentially permit precise modifications on resident genes; (d) automation of phenotyping that allows faster and more complete monitoring of many traits on relatively large plant populations; (e) functional characterization of an increasing number of genes involved in the control of development, berry metabolism, disease resistance, and adaptation to environment. Difficulties involve: (a) the perennial nature and the large size of the plant that makes field testing long and demanding in manpower; (b) the low efficiency of transformation, regeneration and small size of breeding populations; (c) the complexity of the adaptive traits and the need to define more clearly future ideotypes; (d) the lack of shared and integrative platforms allowing a complete appraisal of the genotype-phenotype-environmental links; (e) legal, market and consumer acceptance of new genotypes. The present chapter provides an overview of suitable strategies and challenges linked to the adaptation of viticulture to a changing environment