No abstract

Citrus bark cracking viroid (CBCVd), formerly known as pathogen in the genus Citrus and first detected in Slovenian hops in 2014, threatens hop production as it leads to important economic losses. Reduction in yield and quality and even death of the infected plants within a few years are typical observations due to CBCVd infections of hops. The viroid is easily transmitted and spreads rapidly. As it cannot be controlled by plant protection measures, avoiding its introduction into hop gardens and eradicating first centres of infection are of utmost importance. An indispensable prerequisite is a reliable detection method suitable for large-scale routine testing. In this study, the development of primers and probe for real-time RT-PCR for sensitive CBCVd detection is described. To exclude "false negative" results, a nad5 mRNA-based internal positive control was included. To our knowledge, this is the first time such a duplex real-time RT-PCR detection method for CBCVd at least in hops is described. In addition, first method validation data are presented.

Toxic cyanobacteria such as Microcystis aeruginosa are a worldwide concern in freshwater reservoirs. Problems associated with their mass occurrence are predicted to increase in the future due to global warming. The hepatotoxic secondary metabolite microcystin is of particular concern in this context. This study aimed to determine whether co‐occurring microorganisms influence the expression of microcystin biosynthesis genes. To this end, we performed cocultivation experiments and measured mcyB and mcyD transcripts in M. aeruginosa using RT‐qPCR. We utilized representatives from three different plankton groups: the picocyanobacterium Synechococcus elongatus, the unicellular flagellate grazer Ochromonas danica, and virioplankton from two different lakes. The presence of S. elongatus significantly increased mcyB and mcyD transcription in M. aeruginosa. Cocultivation with the mixotrophic chrysophyte O. danica did not increase the transcription of mcyB and mcyD; in fact, mcyD transcripts decreased significantly. The virioplankton size fraction of environmental water samples induced a significant increase in mcyB and mcyD transcription when obtained from lakes with cyanobacterial blooms. Our results show that co‐occurring microorganisms influence the expression of microcystin biosynthesis genes in M. aeruginosa.