Selection of New Grape Varieties and Clones Flashcards
Grapevine Breeding Background
takes origin when humans selected seedlings (including those spontaneously growing in forests); over a thousand-year activity, growers worked to improve ampelophraphic platform; simple principle- identify and propagate only best vines
Breeding post Phylloxera
since Phylloxera colonized Europe (first seen in French vineyards 1860), grapevine breeding was extended to intraspecific hybrids, obtaining first rootstocks by suing phylloxera-resistant American species: Vitis riparia, Vitis rupestris, Vitis berlandieri
Productive Hybrids
started when breeders tried combining resistance to Phylloxera with new resistance traits observed in other American Vitis (mainly powdery and downy) with Vitis vinifera fruit quality
Main Goals of Grapevine Breeding
resistance to fungi, pest, virus, nematodes, bacteria; resistance to freezing, frost, drought; fruit quality; regular productivity; improve tolerance to BSN, chlorosis, etc.; other agronomic issues
Role of Breeding
increase variability in populations; selection of new genotypes with improved adaptability; rediscover, protect and create biodiversity; provide new material allowing adaptation to market evolution
Grapevine Breeding Methods
traditional- mass selection, clonal selection, intraspecific crossbreeds, interspecific hybrids; innovative- assisted selection (cell and tissues in vitro culture), protoplast fusion, somaclonal variation, gene transfer (Transgenesis and Cisgenesis)
Intra-varietal Variability
clonal selection and, most in general, traditional breeding methods (agamic propagation) are driven by genetic variability (morphological and physiological) that can rise within grapevine varieties
Genetic Variability is due to
polyclonal origin of grapevine varieties; long erm accumulation of genetic mutations
Polyclonal Origin of Grapevine Varieties
intra-varietal variability is realted to presence of many genotypes within grapevine variety; within population of given cultivar a certain number of individuals with different genetic makeup as compared to true type can be identified; this variability results by seedlings obtained by spontaneous crossing between given variety and other unknown varieties
Somatic Mutations
one of main source of diversity within grapevine variety; in a given bud, mutations affect genetic make-up of meristem cells
Source of Somatic Variation
viruses, ionizing radiation, thermal shock or mechanical trauma, physical and chemical mutagens (ex. colchicine)
Morphological and Physiological Differences shown after mutant is Agamically Propagated
differences are such as not to allow clear distinction between mutant plant and parent material; consequently included in genetic variability of each grapevine variety; sometimes bud mutation induces strong and stable variation of genotype giving rise to new variety (ex. Pinot Noir –> Pinot gris –> Pinot blanc)
Factors influencing different levels of Intravarietal Variability
time span- during which grape variety was developed; spatial diffusion
Spacial Diffusion
varieties grown over long time and/or having large diffusion in several viticultural regions are associated to high intravarietal variability; varieties planted by a few years on small area have not yet accumulated enough somatic mutations such as to increase genetic variability of specific variety (*these are considered monoclonal!)
Mass Selection
identification (by empiric method) of grapevines from which collect scions for propagation; positive- identification of grapevines showing positive traits concerning growth and productivity, tagged vines will be only one where buds will be collected; negative- identification of grapevines showing negative traits concerning growth and productivity, will be tagged and excluded during bud sampling process
Clone
population of individuals obtained by vegetative propagation of just one individual isolated within a variety; population of vines all derived by vegetative propagation from cuttings or buds from single mother-vine by deliberate clonal selection
Clonal Selection aims
performed within grapevine population (same varietal) in order to- IDENTIFY healthy grapevines showing improved agronomical and/or enological traits as compared to average of variety, VERIFY stability and genetic basis of such characteristics by mid-to-long term assessment, CHECK HEALTH STATUS of mother-plant-derived material before propagation, PROPAGATE healthy and homogeneous selected material for establishing new commercial vineyards
High Selective Pressure
clones with high adaptability to different environment and wine styles; combination of several positive characters in single individual not easy to achieve; because positive and negative characters are frequently associated, many individuals are excluded; cause of genetic erosion is a dramatic reduction to intravarietal variability of genotypes subjected to clonal selection
Low Selective Pressure
aims to preserve morphological and functional variability of varieties subjected to clonal selection; protection of minor traits are difficult to determin; reduces interaction between genotype and environment (higher stability in different environments over years)
