Question about agreement

Question

Dans la phrase, "N'ajoute aucun ingrédient qui nuirait à l'équilibre du plat, quelle que soit son originalité ou sa rareté.", le mot ’quelle’ fait référence à  quoi ?  Ingrédient ( aucun agrément), originalité ?  Merce de votre explication en avance.

Maarten Kamp · Accepted Answer

Frank,
  "N'ajoute aucun ingrédient qui nuirait à l'équilibre du plat, quelle que soit son originalité ou sa rareté."
The agreement of  ‘ quel (que soit) noun ‘ is with the noun/s it relates to - that is the subject of ‘ soit ‘ .
This is a ‘ compound conjunction ‘ - the subject follows the verb and in this sentence the subject is ‘ son originalité ‘ or ‘ sa rareté ‘ - both feminine singular.
The indefinite adjective ‘ quel ‘ follows the normal rules of adjectival agreement with the noun. 
There is effectively only 1 subject at a time with the use of ‘ ou ‘, giving rise to the use of the feminine singular ‘ quelle ‘ in the expression, as both are grammatically feminine singular.

Frank Cooke · Answer

What if the compound subject consisted of a feminine noun and a masculine noun ?  Would we then use quel ?

Maarten Kamp · Answer

Frank,

The normal rules of agreement apply, so, yes, in French that means a mixed gender choice results in use of the masculine form. This applies regardless of the order of the nouns in the phrase.

So if you had, for example “ son originalité ou son prestige “ (feminine singular + masculine singular)

you would use ‘ quel que soit son originalité ou son prestige. ‘