Fungal and bacterial epiphytes and endophytes have been recovered from grapevine pruning wounds and potential biocontrol isolates were identified using both morphological and genetic characters. The retrieved isolates have been tested both in vitro and in planta as potential antagonists against Botryosphaeria sp. and Eutypa lata. Among the fungal isolates, Cladosporium sp., Penicillium sp., Trichoderma sp. and Aureobasidium sp., showed inhibitory in vitro activity against Botryosphaeria spp. Macroscopic observations suggested that the inhibition of pathogen growth could be due to secretion of antifungal metabolites. A direct mycoparasitism was also observed shortly after the pathogen was put in contact with the antagonist. A preliminary screening for antagonistic bacterial isolates was done considering radial growth inhibition zone, inhibition of mycelium growth, inhibition of spore germination and production of volatile antifungal compounds. Among all the bacterial isolates tested, one strongly inhibited pathogen mycelial growth. Furthermore, both fungal and bacterial endophytes/epiphytes as well as new experimental products were tested in vitro for their ability to protect grape wood chips from pathogen colonization. Standard fungicides normally used in the control of grape canker diseases were used as reference controls. Based on these tests we have identified new microorganisms and experimental products that function on the wood surface longer than the fungicide mixture used as a reference. These promising in vitro results have been confirmed by the first year field trial. Topsin+Rally, B-LOCK and Elite, among all treatments, offered the best level of control of the pruning wounds against Botryosphaeria sp. Among the bio-control organisms, the fungi Cladosporium sp. and Penicillium sp., exhibited levels of control similar to that of the fungicides used as references. The bacterial isolate was better than fungi and chemistry in preventing infection by either Eutypa or Botryosphaeria spp. Based on the obtained results we have been able to assess the optimal application time of biological agents in order to guarantee an adequate protection of the pruning wounds. In fact, the antagonist organisms need to fully colonize the pruning wound surface in order to function against canker pathogen infections. New experimental products for the control of the disease are also under field investigation and the preliminary results were excellent and their potential to be registered as new commercial products is good. We are also evaluating dormant fungicide treatments using spray applications by tractor for canker disease prevention under ?natural? disease pressure. A fungicide trial (second year) is being conducted in a vineyard in Napa County as a five year study to asses this tractor application objective. As far as the investigation on the secondary metabolites produced by L. theobromae is concerned, we have identified 17 specific metabolites which appear to be related to the maturity and developmental stage of the cells within the colony and thus might be associated with different metabolic processes during the life of the organism. These molecules bear very stable structures, typical for cyclic and aromatic compounds. Further elucidation needs accurate mass spectrometry to determine elemental compositions and to investigate the role of these metabolites in the infection process. Finally, we have shown that Phomopsis spp. contribute to grapevine canker formation. All isolates tested in fact, were pathogenic towards six different grapevine cultivars being capable of causing V-shape cankers in the inoculated canes.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF2010-10-16 06:45:462017-10-16 06:46:40Grapevine Canker Diseases in California