A preliminary study of clonal selection in cv. Viura in relation to varietal aroma profile

Abstract

Viura is a synonym for Macabeo and currently it is the most widely planted white grape variety in D.O.Ca. Rioja, with 3,569 ha, representing 84% of the white grape cultivated area. It is a generous-yielding grape, presenting low values of titratable acidity and with large and compact clusters which makes it susceptible to Botrytis cinerea. Thus, this variety not always satisfies the wine grower’s prospects. Nowadays, the available plant material is scarce, moreover, it was selected on the basis of other quality criteria, not currently requested. Cv. Viura is suitable to elaborate white dry wines and also sparkling wines together with other varieties. Floral and fruity aromas are the ones more representative of cv. Viura, although they appear with a medium level intensity. Grape volatile composition is one of the most important parameters determining must and wine quality. Wine aroma is formed by volatile compounds of different chemical natures and origins and they vary as a function of several factors, being the variety a key factor. For it, in order to characterize the aroma profile of cv. Viura and provide to the market new certified plant material, a clonal selection with 106 clones of cv. Viura was carried out. These clones, belonging to different cultivated areas of D.O.Ca Rioja, were planted in a comparative field of clones. Agronomical and technological characteristics were evaluated during three consecutive years, selecting on the basis of these parameters 41 clones that showed low production and high values of titratable acidity. The volatile compounds of these clones were analyzed by HS-SPME-GC-MS. The results showed that C6 compounds, norisoprenoids and terpenoids were the most representative in cv. Viura, showing C-6 compounds a great variability within clones. Concerning each group, 24% of the studied clones highlighted by presenting a higher content of C6 alcohols in relation to their average content, being the most representative compounds (E)-2-hexenal, hexanal and 1-hexanol. These compounds, depending on its concentration, can have a detrimental effect on wine quality due to their grassy and herbaceous odors. Approximately the 50% of clones exhibited a higher content of norisoprenoids and terpenoids in relation to their average content. (E)-β-damascenone, β-ionone and (Z)-β-damascenone were the most abundant norisoprenoids compounds and linalool, nerol oxide and α-terpineol the most abundant terpenoids. Both, norisoprenoids and terpenoids are among the most odoriferous groups of compounds, emitting floral scents which allow characterize the varietal aroma. Sixteen clones out of forty one presented the highest content of these two positive groups of compounds, being considered the ones with the better varietal aroma profile. These results obtained can be of great interest to wine sector due to the increase of supplied certified plant material of this variety which contributes to improve its wines quality.