Protection of Highbush Blueberry Plants against Phytophthora cinnamomi Using Serendipita indica

A greenhouse experiment was carried out on the use of Serendipita indica, an endomycorrhizal-like fungus, to increase the resistance of three highbush blueberry cultivars Chandler, Darrow and Spartan to the pathogen Phytophthora cinnamomi. The cultivars differed in the acceptance of root colonisation by S. indica and in susceptibility to P. cinnamomi. The lowest percentage (%) of colonised roots was found in the cultivar Spartan. The frequency of symptomatic plants (stunted growth, dark spots on stems, small, yellowing, and dropping leaves) among plants inoculated only with P. cinnamomi was 59, 83, and 100%, for 'Chandler', 'Darrow', and 'Spartan', respectively. In the treatment where both pathogen and endophyte were inoculated, the frequency in 'Darrow' and 'Spartan' dropped to 28 and 90%, respectively. Of non-protected 'Spartan' plants, 66% died, whereas only 14% of those protected with S. indica died. Colonisation by S. indica reduced the number of dead plants of 'Chandler' from 3 to 1 among those protected. In 'Darrow' only one plant died of the non-protected and none of the protected ones. S. indica increased the growth of non-infected plants of 'Darrow' and 'Spartan' by 11%. An increase in the growth of plants inoculated with S. indica and infected with P. cinnamomi after 21 days went from 74% to 182% over the plants only infected with the pathogen.