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POSTERS: New and Emerging Diseases I

P-447 - Bacterial Leaf Spot of Southern Highbush Blueberry (Vaccinium corymbosum) Caused by Xanthomonas euvesicatoria

Monday, August 4, 2025
4:30 PM - 5:15 PM HST
Location: Exhibit Hall 3
Abstract Text: Blueberry, a well-known superfruit from the Ericaceae family, is rich in nutrients and welcomed by the public. Although several cultivars have been selected for commercial production in Taiwan and the acreage has increased recently, knowledge about diseases threatening the industry remains limited. In 2023, young leaves of highbush blueberry showing irregular water-soaking dark spots were observed in central Taiwan. The lesions turned brown to red on leaves, eventually becoming necrotic lesions restricted by leaf veins. Three bacterial strains were purified from symptomatic leaves. All strains were rod-shaped Gram-negative bacteria, which could induce a hypersensitive response on tomato and tobacco leaves. Further biochemical and physiological tests of the 3 strains on differential media exhibited similar characteristics with Xanthomonas species. All bacterial strains caused symptoms on blueberry leaves between 15-45℃ after 20-25 days of inoculation, and the same bacteria were re-isolated from diseased leaves, fulfilling Koch’s postulates. The 16S ribosomal DNA sequencing identified the strains as Xanthomonas sp. A multilocus sequence analysis further clustered the 3 strains with known pathovars of X. euvesicatoria, and were phylogenetically distant from the X. arboricola and X. campestris previously reported on blueberry. Considering the potential threat posed by this pathogen, the diseased blueberry plants were eradicated. Further studies on the host range and management approach of the pathogen are warranted to help prevent unexpected outbreaks of the disease in Taiwan.