WINETECH Technical Yearbook 2021

thousands of seedlings from hundreds of crosses. Selected vines are then used in subsequent crosses, and backcrosses, resulting in numerous generations before breeders obtain the desired outcome. A far cry from the romantic idea conjured when considering Perold’s intuition-driven cross. A major aim of the last 50 years of international grapevine breeding has involved the incorporation of mildew- (and other pathogen-) resistant traits from wild Vitis relatives into premium vinifera cultivars. Progeny raised from these first- generation crosses seldom produce high quality wines, but with time breeders have backcrossed promising material and have steadily incorporated more and more premium vinifera qualities into resistant material. However, the pathogens are not so easily defeated, and quite quickly mildew strains evolved to overcome the newly added resistance. Scientists realised that to prevent pathogen evolution, it was necessary to incorporate several genetic elements simultaneously into a single plant. This approach was made possible due to several advancements in grapevine genetics over the past thirty years, and in particular the sequencing of the grapevine genome. Plant scientists first identified genetic elements in wild cultivars that gave resistance against pathogens, and then

designed so-called DNA markers which can track the presence of the DNA linked to the desirable trait, such as mildew resistance. Breeders then use this knowledge and make directed crosses, incorporating the genetic elements in subsequent generations. By using DNA markers, breeders confirm the presence of the resistance gene at an early stage, greatly accelerating and streamlining the breeding process. These DNA marker tests can be carried out in hours, and on newly-germinated grapevine seedlings. Thus, by employing this technology, known as marker-assisted breeding, breeders have successfully been able to add DNA from multiple wild species into new “resistant” cultivars, in a process known as gene pyramiding (figure 1). In Europe and the USA the first of these novel cultivars have been released to growers and wine is being produced and sold. One of the biggest perceived obstacles in getting these new wines to market has been the pervasive idea that consumers would not be willing to give new cultivars a chance. However, research from France has found that while consumers initially had difficulty accepting wine made from these novel cultivars, these perceptions changed after having the wine’s origins described. After being informed about the reduced environmental impact and

FIGURE 1. Illustration of the multiple generations required when breeding novel cultivars to contain multiple resistance genes. Molecular tests can be used to determine the incorporation of the resistance genes (marker-assisted selection), but each generation can take up to seven years resulting in over 20 years between making the first cross and creating a wine from the final premium resistant cultivar.

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