FIRST REPORT OF PHYTOPHTHORA CINNAMOMI CAUSING ROOT ROT OF SOUTHERN HIGHBUSH BLUEBERRY IN CALIFORNIA
Aidan Shands1, Jesse Yamagata1, Timothy Miles1, Amanda Wright2.
1California State University, Monterey Bay, Seaside, CA, 2Plant Pathology, Driscoll's, Watsonville, CA.
Phytopthora cinnamomi Rands is a common soil-borne pathogen known for causing root rot, wilting, and yellowing of foliage, often leading to death of a multitude of plant species around the world. In 2015, several southern highbush blueberry plants (Vaccinium corymbosum L.) growing in Oxnard, California, were stunted, chlorotic, and had necrotic, blackened roots. Samples were collected, isolated, and later identified morphologically as Phytopthora cinnamomi. To confirm pathogenicity, 10 3-month-old asymptomatic southern highbush blueberry plants were propagated in tissue culture and separated into a control and test group. The inoculum was prepared by growing the P. cinnamomi isolate 14-009 in potato dextrose broth for 7 d on a laboratory shaker at room temperature (RT), harvested, and blended. The control and inoculated plants (n = 5) were exposed by dipping the plant roots in water or suspended mycelium. After a 7-day incubation period, inoculated plants showed symptoms of yellowing, stunted growth, and a 48% reduction in the number of leaves while the control plants showed no evidence of infection. The roots were taken from both samples, weighed, and reisolated and DNA tested and confirmed for the presence of P. cinnamomi, effectively concluding that P. cinnamomi was causing root rot of southern highbush blueberry. To the best of our knowledge, this is the first report of P. cinnamomi infecting blueberry plants in California and, in the future, it should be considered when making management decisions (e.g., rotational crops).