The molecular characterization of HSVd isolates associated with dapple fruit and fruit rugosity in plum seedlings suggests a possible role of breeding in viroid dissemination

Abstract

In a wide range of hosts, the infection caused by Hop stunt viroid (HSVd) appears to be latent, whereas in some others it is frequently pathogenic. In this work, the presence of HSVd has been found to be associated with symptoms of dapple fruit and fruit rugosity in plum seedlings obtained from cross breeding for quality. Symptomatic and symptomless plum seedling samples have been analyzed for the presence of the principal stone fruit viroids and viruses. HSVd was found in all symptomatic samples, whereas no other viruses or viroids were found in the analyzed samples with the exception of ACLSV, which was detected rarely. The RNAs of all HSVd isolates have been cloned and sequenced. The sequence analysis showed a high percentage of homology among the isolates, making it possible to hypothesize a potential unique origin of the infection. For this purpose, those plants used in breeding as pollen donors have been analyzed. The results showed that the same HSVd isolate was also present in the parental plants, both in the leaves and pollen, suggesting a possible role of breeding in the dissemination of the viroid.

Keywords: Plum, seedlings, fruit rugosity, dapple fruit, HSVd, pollen