Bacillus amyloliquefaciens and Trichoderma atroviride could be competitive for removing opportunistic pathogens such as Gnomoniopsis smithogilvyi from Castanea sativa grafting scions
Abstract: A search for endophytes in Castanea sativa grafting scions showed that an opportunistic pathogen, Gnomoniopsis smithogilvyi, was present as the major component of the endophytic flora. Already know in Italy and Australia as a pathogen affecting the chestnut fruit, we described it elsewhere as the cause of canker symptoms very similar to the one caused by Cryphonectria parasitica on twigs and scions. For a preventive biocontrol experiments, scions of C. sativa were soaked overnight in a liquid suspension of Bacillus amyloliquefaciens strain P1. This bacterium was then frequently found in the low parts of scions and up to 18 centimetres height. It has been observed that when B. amyloliquefaciens was present, the endophytic and opportunistic pathogenic fungus G. smithogilvyi was not present. Conversely, the parts not colonized by the bacteria were always naturally infected by the endophytic fungus. This would indicate that the endophytic behavior of B. amyloliquefaciens inhibited the growth of G. smithogilvyi and reduced its presence in chestnut scions. A similar experiment was carried out with the biological control agent Trichoderma atroviride strain ITHEC45 and the same phenomenon has been observed. T. atroviride was frequently found in the lower parts of scions and up to a 27 centimetre height. Inoculating B. amyloliquefaciens and T. atroviride as part of preventive biocontrol treatment’s is promising because their endophytic behaviour would allow these BCAs to colonize the plant and prevent the development of pathogens.