Nutritional niche overlap potentiates the use of endophytes in biocontrol of a tree disease

Asymptomatic endophyticfungi are often regarded as potent biocontrol agents in plants, but the competitive interactions between endophytesand other microbes within the same host plant are poorly understood. We tested a hypothesis that as compared to asymptomatic endophytes, an aggressive pathogen inhabiting the same host is able to utilize carbon substrates more efficiently. Using phenotype microarray, we determined the carbon utilization profiles of the highly virulent Dutch elm disease(DED) pathogen Ophiostoma novo-ulmi, and four asymptomaticelm (Ulmus spp.) endophyteisolates that were selected based on their differential associationto the DED-susceptibility pattern of the host elms. The competitive interactions between isolates were evaluated using a niche overlap index. In contrast to our hypothesis, the studied endophytesexhibited extensive niche overlap with the pathogen, suggesting that some endophytestrains might protect elms against DED-pathogen through competition for substrates and provide new tools for biocontrol of DED.