A viroid is infectious._.

Explanation

Viroids are the smallest known infectious agents, consisting solely of a short, circular strand of single-stranded RNA without any protein coat or envelope. Unlike viruses, viroids do not encode proteins and rely entirely on the host plant's cellular machinery for replication. They primarily infect plants, causing diseases by interfering with normal gene regulation and cellular processes. Viroids are capable of autonomous replication within the host but lack the structural components of viruses, such as capsids or envelopes, making them unique among infectious agents. Their simplicity and high replication rate can lead to significant agricultural losses in infected crops.