A New Ranunculus Disease Caused by Xanthomonas campestris . H. R. Azad, Staff Research Associates, Department of Plant Pathology, University of California, Riverside 92521. M. Vilchez, Staff Research Associates, A. O. Paulus, Plant Pathologist, and D. A. Cooksey, Professor, Department of Plant Pathology, University of California, Riverside 92521. Plant Dis. 80:126-130. Accepted for publication 24 October 1995. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0126.

A new disease of ranunculus (Ranunculus asiaticus) was observed on several cultivars in commercial fields in San Diego and Riverside Counties, California. Symptoms included pin-point to large irregular necrotic lesions on leaves and steins and occasionally black patches along the internal margins of leaflets in association with vein chlorosis. Xanthomonas campestris was consistently isolated from diseased tissues. X. campestris was also isolated from tubers and seeds of naturally infected plants, which suggests a means by which the pathogen is spread in the industry. One-year-old tubers of two cultivars (Picotee and Rose) were contaminated at frequencies of 4 and 7%, respectively. The frequency of seed contamination for 11 cultivars ranged from 1.1 to 16%. Symptoms appeared on inoculated ranunculus plants as early as 3 and as late as 22 days after inoculation, depending on the method of inoculation, temperature, and available moisture. Recovery of the bacterium from (he tubers of plants inoculated and kept under different moisture and temperature conditions was 6.6 to 13.3%. Amplification of a DNA fragment specific for hrp genes by polymerase chain reaction for each strain and further analysis of the amplification product by restriction endonuclease digestion suggested that the ranunculus strains were closely related to each other and to X. c. pv. campestris; however, pathogenicity tests indicated that the ranunculus strains could be a different pathovar