Phenotypical variation in peach trees inoculated with defined mixtures of viruses and peach latent mosaic viroid

Although individual viruses and viroids may produce diagnostically distinct phenotypic variations (signs and symptoms) when infecting trees as single entities, infection by more than one of the same viruses or viroids may produce novel and/or previously unrecognized variation in the plant phenotype. To investigate the role of 3 viruses and Peach latent mosaic viroid (PLMVd) in a graft-transmissible bloom delay observed in peach (Prunus persica (L.) Batsch), trees of 'Springprince' were planted in a high-density, Y-trained orchard system and inoculated using chipbuds containing Apple chlorotic leaf spot virus (ACLSV), PLMVd, Cherry green ring mottle virus (CGRMV) and an uncharacterized Foveavirus referred to as Asian prunus virus (APV) alone or in various combinations. DASI-ELISA, dot-blot hybridization and RT-PCR systems were used to verify transmission of these infectious agents from the chipbuds to the 'Springprince' trees. Three replicates of 4-tree plots for each of 11 defined mixtures of viruses and viroid treatments were established. Phenological developments including leaf abscission, fruit set and flowering time were monitored to compare the effects of defined multiple and single inoculations. In addition, horticultural characters such as trunk cross-sectional area, fruit weight and tree yields were recorded. Mixed virus and/or viroid combinations resulted in accelerated bloom progression, increased fruit set and greater fruiting efficiency.