The potato spindle tuber viroid (PSTV) is the first identified viroid. It causes potato tuber spindle disease in potato plants, which results in delayed sprouting and physical deformities such as abnormal, lumpy growths.

Potato Spindle Tuber Viroid

Tomato planta macho viroid (TPMVd) is a plant pathogen that infects tomato crops. It causes symptoms such as disfigured and brittle leaves, loss of chlorophyll, and extremely small tomatoes, which severely reduces crop productivity.

Tomato Planta Macho Viroid

Avocado sunblotch viroid (ASBVd) is the smallest known plant-infecting viroid. It causes disease in avocado plants, resulting in reduced fruit yields and poorer-quality fruit.

Avocado Sunblotch Viroid

Peach latent mosaic viroid (PLMVd) causes necrosis of flower buds and branches, and wounds ripened fruit, making it susceptible to secondary bacterial and fungal infections. In addition to peach trees, PLMVd infects plums, nectarines, apricots, and cherries, causing reduced productivity in these orchards.

Peach Latent Mosaic Viroid

Viroids are spread mechanically during agricultural crop maintenance and harvesting, as well as through vegetative reproduction. They may also be transmitted via insects and seeds, potentially causing severe agricultural losses and devastating economic impacts.

Dispersal of Viroids

Viroids are acellular, infectious agents consisting only of small, naked single-stranded RNA (ssRNA) molecules, which cause diseases in plants.

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Nonliving disease agents are acellular pathogens, such as viroids, virusoids, and prions, that are entirely distinct from viruses. These agents consist solely of RNA or proteins, yet they share the viral ability to self-propagate by utilizing host cell machinery to cause disease.

Nonliving Disease Agents

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Viroids

Virusoids are pathogenic, subviral particles composed of single-stranded RNA (ssRNA) that infect commercially important agricultural crops. Unlike viroids, virusoids are non-self-replicating and require the host cell to be co-infected with a specific helper virus to undergo replication.

Virusoids

Satellite RNAs are pathogenic, single-stranded RNA molecules found in animals that require coinfection with a helper virus to replicate. Unlike plant-infecting virusoids, some animal satellite RNAs are capable of encoding their own proteins.

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