Crown and root rot of highbush blueberry caused by Phytophthora cinnamomi and P. citrophthora and cultivar susceptibility

Abstract

Chile is the largest producer and exporter of blueberries in the southern hemisphere. During the 2006-2007 growing season, blueberry production increased in Chile as a result of an expansion of the planted area, reaching around 10,762 ha in 2007. Fungal diseases are of great importance in blueberry production; among them, Phytophthora root rot is a disease known worldwide as a major cause of death for highbush blueberry plants in the USA. Symptoms of Phytophthora root rot have been detected over the last four years in Chile. Nevertheless, the causal agents have not been previously described in Chile. This study aims to determine the pathogenicity of Phytophthora spp. isolated from highbush blueberry and to study cultivar susceptibility. The pathogenicity tests show that the species P. cinnamomi and P. citrophthora were the cause of crown and root rot of highbush blueberry. Signifi cant differences in plant height, shoot growth stem diameter, and fresh weights of roots and aerial parts between inoculated and non-inoculated plants were observed. Blueberry cv. ‘Toro’ was the only cultivar resistant to P. cinnamomi, while both ‘Elliot’ and ‘Toro’ were resistant to P. citrophthora. Regardless of the Phytophthora species, cv. ‘Biloxi’ was the most affected. This is the fi rst report of Phytophthora root rot in Chile and, to our knowledge, the fi rst report of P. citrophthora affecting blueberry plants worldwide. Key