In modern grapevine breeding, we use marker-assisted selection (MAS).
MAS is a very efficient diagnostic method that helps to determine breeding-relevant traits of young seedlings on a genetic level at an early stage in the breeding process. This also allows selection decisions to be made much earlier. For trait-linked marker development, genetic maps are generated and correlated with the phenotypic variation of the trait of interest (e.g. resistance, quality), enabling to identify which gene loci are responsible for the expression of a trait.
Molecular markers for breeding are currently being developed for the following fields:
New resistances are being identified and genetically mapped for the most important fungal pathogens with the highest damage potential, downy mildew (Plasmopara viticola), powdery mildew (Erysiphe necator), grey mould (Botrytis cinerea) and black rot (Guignardia bidwellii), as well as the pest phylloxera (Daktulosphaira vitifoliae). With the help of MAS, we can combine new resistances with existing resistance-conferring gene loci in new varieties (stacking of resistances), resulting in increased and long-term field resistance. In addition to genetic resistances based on classical resistance genes, we also work on physico-morphological aspects that make the grape variety more resistant. Less dense bunches, firm berry skin, a water-repellent wax layer or leaf hairiness are examples. Sensor and AI-based methods are increasingly being used for trait evaluation.
Sunburn on grapes is now occurring more frequently as a result of the heat events of recent years. Very high temperatures/UV radiation during grape ripening damage the berries, which can lead to yield and quality loss. In the Institute's genetic resources and cross-breeding populations, clear varietal differences in susceptibility could be documented. Laboratory tests allow a representative, objective and precise evaluation of mapping populations and selected breeding material. Based on the results, first genetic regions related to the expression of sunburn resistance have been identified.
Successful new varieties must be adapted to the climatic conditions of their cultivation areas. Late budding reduces the risk for late spring frost damage. Flowering time and véraison (beginning of berry ripening) significantly control the ripening window and thus influence harvest time and achievable wine quality. First gene loci for budding, flowering time and véraison have been detected, thus laying the foundation for a specific marker development.
The requirements for yield parameters and wine quality of new varieties are very high and measure up to established varieties. Yield parameters such as number of shoots, inflorescences or berries, as well as individual bunch architecture characteristics are increasingly collected by sensor-based methods and used in genetic studies. Environmentally independent genetic markers for wine quality can be developed from analytically and sensorially collected data of wines that have been produced over several years in microvinifications. Negative genetic characteristics (e. g. off-flavours) of wild grapevines can be removed at an early stage in the breeding process and positive quality alleles can be enriched. An estimation of important grape characteristics, such as wine quality parameters, yield stability as well as attributes like harvest time via breeding markers (MAS), long before a plant develops its first grapes would be of high value to increase breeding efficiency.