ECO-PHYSIOLOGICAL CHARACTERIZATION OF NEW GRAPEVINE ROOTSTOCKS UNDER DROUGHT STRESS
Creators: name: GROSSI, DANIELE
Publisher: name: Universit� degli Studi di Milano
Year: 2015

description: Extended Abstract ECO-PHYSIOLOGICAL CHARACTERIZATION OF NEW GRAPEVINE ROOTSTOCKS UNDER DROUGHT STRESS The objectives of grapevine rootstock breeding selections have undergone a continuous evolution over the years. From the first American vine species introduced to face the invasion of phylloxera and the mildews through Europe, recent breeding programmes aims to obtain plants which are also tolerant to biotic and abiotic stresses such as nematodes, drought and salt stress. Furthermore, the main present interest is on rootstocks that show good performance in different places and in favorable years, but that maintain a good efficiency in difficult conditions. The selection of grapevine rootstocks for resistance to drought conditions is particular important across the activities of modern breeding. Water stress tolerance but above all the water use efficiency (WUE) is becoming more and more important cause the variability of the environmental factors such as limited availability and irregular distribution of water resource. The achievement of the objectives of selection is closely linked to the efficiency and quality of characterization of the phenotype under stress conditions. Traditional phenotyping techniques, although consolidate and widespread, showed considerable limitations like time-consuming and destructive methods. Current technologies allow the development of new systems named high-throughput phenotyping techniques. Thermography, detecting heat patterns in the infrared-wavelength spectrum, is one of the techniques applied in viticulture to assess the plant water conditions. In addition to phenomics techniques, the detection of changes at the molecular level related to the ability to modify the phenotype under stress also play key roles. The analysis of the changes in gene expression induced by water stress is part of this evolution and the analyses of the transcriptional regulation of some genes involved in the responses to water deficiency shown particular interests. The present work aims to characterize the eco-physiological responses of new grapevine rootstocks under water stress in comparisons with the most widespread commercial rootstocks and other genotypes of Vitis spp. In particular the study focuses on the strategies in response to water stress and how these modifications can be transmitted to the scion by the rootstock. The first goal achieved has been the validation of the methods used in high-throughput phenotyping. Thermography has proven a valuable tool in order to assess the water condition of the plant and its evolution during the experiments. The effects of water stress on the variation of stomatal conductance and the rate of growth of the plants have been confirmed allowing the acceleration in phenotyping. It was also possible classify the different behaviors in response to water stress conditions providing a database of phenotypic information to be associated with genotypic data. This point has been particularly important as support to genetic association studies (GWAS) aimed to develop molecular markers to assist and optimize future breeding programs of grapevine rootstock. Another aspect observed is how the rootstock is able to influence some of the main responses to water stress and how these effects characterize the behavior of grafted variety. In particular several combinations of rootstock with the same scion have been compared: five of the most widespread commercial rootstocks and four new developed rootstocks has been tested under a dry down experiment under controlled greenhouse conditions. Changes in the eco-physiological status of plants in response to different levels of water stress has been evaluated. The rootstocks have been able to influence the responses to water stress in terms of stomatal conductance (Gs), net photosynthesis (Pn) and stem growth rate (SGR). The modification of gene expression in the roots of the different rootstocks and in the leaves of the scions have also been determined. The differences were observed on transcripts involved in the phenylpropanoid biosynthesis and relative transcription factors involved in the regulation of this pathway, stilbene synthases pathway and on the expression of abscisic acid (ABA) related genes. The analysis of transcriptional regulation of secondary metabolism has been considered as the main responses involved in the role of protection against oxidative stress induced by drought conditions. In conclusion, the rootstock has determined a different response according to the genotype but also was able to develop different responses in the scion. This shows that the biosynthetic pathways of ABA, stilbene and flavonoids synthases involved in scion response to drought conditions can be controlled by the rootstock.