Step 1: In 1971, while studying potato spindle tuber disease, Diener found that the disease agent passed through filters that would stop even the smallest viruses and lacked any protein coat.
Step 2: He characterised it as a small, circular, single stranded RNA molecule capable of self replication inside a host cell without needing a capsid, and coined the term viroid for this new class of pathogen.
Step 3: Nucleosomes were described by Kornberg's group in chromatin research, and heterospory is a botanical concept in seed plant evolution, both unrelated to Diener's work.
The correct discovery attributed to Diener is viroids.