Multiple small RNA species and the viroid hypothesis for the sunblotch disease of avocado.

Multiple RNA species (ASV(1-5)) ranging in size from about 61,000 to 185,000 daltons have been detected in association with sunblotch disease of avocado. The predominant species, ASV(5), with a molecular weight of 61,000 accumulates to concentration approaching 5 S RNA. All RNA species are detected in extracts from symptomatic tissue of avocado var. Fuerte but not from asymptomatic tissue of the same leaves from which the disease agent can be transmitted to avocado. The probability that the predominant ASV(5) species is either the putative sunblotch "viroid" or a noninfectious "viroid-related" molecule is discussed.