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First Report of Ceratocystis fimbriata-Caused Wilt of Eriobotrya japonica in China

The loquat (Eriobotrya japonica (Thunb.) Lindl.), an important perennial evergreen fruit crop that originated in China and is also cultivated as an ornamental plant, is well known all over the world for high nutritional, medicinal, economic, and ecological values (4). So far, it has been grown in more than 30 countries (1) and is becoming an important industry in China, Spain, Japan, India, Pakistan, and Turkey (2). During an investigation from May to August of 2013, severely withered loquat plants were observed in Kunming city of Yunnan Province (25°02′ N; 102°42′ E), Southwest China. Initial symptoms were brown lesions of leaves and canker on one to several branches, leaves of the whole tree turned wilted. Cross sections of diseased plants revealed irregularly shaped brown discoloration in the xylem of the trunk. A fungus was consistently isolated from the leaf when diseased leaves were incubated between two slices of fresh carrot root. Spore masses were picked from the apices of perithecia and transferred to malt extract agar medium (MEA) and incubated at 25°C. After perithecium formation, observed perithecia were black, globose (176.0 to 303.2 × 186.0 to 274.3 μm) and showed a long black neck (634.2 to 809.9 μm). Ascospore had the typical format of a “hat” with dimensions of 4.6 to 6.3 × 3.3 to 4.8 μm. Cylindrical endoconidia (7.1 to 36.1 × 2.9 to 6.0 μm) were found. Chlamydospores were ovoid or obpyriform and smooth (8.6 to 12.1 × 6.9 to 12.1 μm). PCR amplification was carried out for one isolate, YT2. The ITS region of rDNA was sequenced using the procedures of Thorpe et al (3). Analysis of ITS sequence data (GenBank Accession Nos. KF963101 and KF963102) showed that the isolates were 99% homologous to the isolate of Ceratocystis fimbriata from diseased Colocasia esculenta in Cuba, China, and Hawaii (AY526304 to 06) by BLAST analysis. Therefore, the fungus was identified as C. fimbriata based on morphological and molecular characteristics. Pathogenicity of the six isolates from this study was tested by inoculation of 1-year-old pot grown seedlings of loquat. The soil of six plants was inoculated by drenching with 40 ml spore suspension (10⁶ spores/ml). Control plants were inoculated with 40 ml of sterile distilled water. The plants were maintained in a controlled greenhouse at 25°C and watered weekly. After inoculation for 1 week, all plants produced wilt symptoms; as the disease progressed, leaves withered and died after 3 weeks of inoculation while control plants remained symptomless. C. fimbriata was successfully re-isolated from the infected trees and no fungal growth was observed in the controls. The pathogenicity assay showed that C. fimbriata was pathogenic to loquat. To our knowledge, this is the first report of C. fimbriata causing wilt of loquat in China. Since C. fimbriata is one of the most aggressive plant pathogens on a wide variety of perennial as well as agronomic crop plants worldwide, and the infection can pose a significant threat to the production of loquat, it is critical to deploy appropriate management strategies to limit the fungus spread.

References: (1) J. J. Feng et al. Acta Hort. 750:117, 2007. (2) J. Janick. Acta Hort. 750:27, 2007. (3) D. J. Thorpe et al. Phytopathology 95:316, 2005. (4) J. Yan et al. Pak. J. Bot. 44:1215, 2012.