Distribution of Botryosphaeriaceae species and genotypes within a rootstock mother vine indicates multiple inoculum sources

Abstract

Infected rootstock and scion cuttings by Botryosphaeriaceae fungi have been reported as major sources of infection for young grapevines. To investigate the potential infection pathways of Botryosphaeriaceae species within a rootstock mother vine, a universally-primed polymerase chain reaction (UP-PCR) was conducted. This method differentiated the genotypes within two Neofusicoccum species, namely N. luteum and N. parvum. The first study showed that multiple Botryosphaeriaceae species and genotypes can infect a single mother vine. It further showed that the trunk and shoot isolates of the same species from the same vine were of the same or different genotypes, suggesting multiple infections from different inoculum sources. The second study that investigated the spatial distribution of Botryosphaeriaceae fungi within an entire dormant cane also showed that multiple species and genotypes were distributed along the cane, but most isolates were sited within the bark and less frequently in the wood, suggesting they were latent in surface tissues. Some adjacent wood and bark infections were caused by the same genotypes also suggesting that wood infection may have originated from the bark. The third study further showed that the Neofusicoccum isolates recovered by washing the cuttings were of the same or different genotypes from those isolated from adjacent internal tissues, again suggesting multiple sources of external inoculum. These fungi appear to cause latent infections in the bark of dormant cuttings which are used in plant propagation, thus providing an additional infection pathway for a disease that is known to show obvious symptoms only in older vineyards.