。
Yukiko likes potatoes.
Literal
Yukiko [topic-は] potato [subject-が] liked be-[plain-だ].
The classic Xは Yが好きだ pattern: the topic is the person (experiencer), and the thing liked is marked with が (grammatical subject of 好き). Good reminder that 好き is a na-adjective, not a verb — 'liked' as a predicate. ジャガイモ ('potato') is often written in katakana.