Archivio Journal of Plant Pathology

Abstract:

In July 2009 and October 2012, stems of young peach (Prunus persica) trees with cankers from Kings, Fresno and Yuba Counties, respectively, in California were submitted to our diagnostic laboratory. The cankered areas were discoloured brown in comparison with the creamy healthy bark and covered with gum galls. More than 30 trees were killed in Fresno and Kings Counties, and 6 trees in Yuba County. Scraping the cankers revealed large black pycnidia and brown discoloured wood. A fungus consistently isolated from the cankers was identified as Lasiodiplodia citricola based on morphological characteristics (Abdollahzadeh et al., 2010) and analyses of ITS, and TEF-1α gene regions. The sequence showed high identity (ITS, 100%; TEF-1α, 99%) with reference sequence (isolate: IRAN 1522C = CBS 124707, ex-type of L. citricola; accession Nos.: ITS, GU945354; TEF-1α, GU945340; β- tubulin, not available) for L. citricola (Abdollahzadeh et al., 2010). Sequences were deposited to GenBank (isolates: 7F93, 7F94 and 7F95. Accession Nos.: ITS, KC357262–KC357264; TEF-1α, KC357268–KC357270; β-tubulin, KC357265–KC357267). Pathogenicity of L. citricola in P. persica variety nectarina cv. Summer Fire was tested using three isolates. Ten two-year-old branches for each isolate were inoculated. Inoculations were made in late Oct. 2012 as described by Chen et al. (2013). Lesion length was measured 3 weeks after inoculation. The three isolates of L. citricola produced 60–67-long lesions within 3 weeks, while wounds were covered with callus tissue in the control inoculations. L .citricola was reisolated from the inoculated branches and no fungus was re-isolated from the control branches. These results indicate the pathogenicity of L. citricola to P. persica.