Archivio Journal of Plant Pathology

Abstract:

The oil- and table olive industry in California is growing rapidly. Propagation material is being requested in ever-larger quantities from the USDA National Clonal Germplasm Repository at the University of California, Davis. This collection is recognized as one of the richest sources of olive material in the U.S. The repository maintains 107 different olive varieties imported from 19 different countries. However, the collection’s viral infection status has never been systematically analyzed. We have now completed the first comprehensive virus testing of the collection using molecular diagnostic tools. A total of 49 trees from 36 different cultivars were sampled. Though these trees were asymptomatic, the samples from 97.9% of them showed dsRNA profiles indicating viral infection. The 93.8% of these trees tested positive for Olive leaf yellowing-associated virus (OLYaV; an unassigned virus in the Closteroviridae) by RT-PCR analysis, while 34.7% were positive for Cucumber mosaic virus (CMV). PCR amplicons of the OLYaV heat shock 70 homologue (HSP70h) gene were cloned and sequenced to analyze diversity of isolates from trees originating from different geographical regions. Sequence analysis showed a maximum of 32% divergence between amplicons obtained from these selections.