Archivio Journal of Plant Pathology

Abstract:

A disease of mango (Mangifera indica) observed in 2009-2010 in Hainan and Guangxi provinces (China) is characterized by small water-soaked spots on the leaves turning with age into an- gular, sunken, deep-brown to black necrotic lesions with a yellow halo, whose necrotic tissue may fall, resulting in a “shot-hole” condition of the blades. These symptoms differ from those of mango bacterial black spot caused by X. campestris pv. mangiferindicae (Xcm) (Gagnevin and Pruvost, 2001). Purified bacterial colonies appeared yellow, slimy and convex on YDCA medium, and induced hypersensitive responses on tobacco (HC9511). The field syndrome was reproduced on inoculated mango plants and the same bacterium was reisolated from symp- tomatic but not from control leaves, which remained symptom- less The sequences of 16S rDNA gene fragment (ca.1.4 kb) (JF803830-JF803839) of ten isolates (GXMG2, GXMG5, GXMG8, GXMG9, GXMG10 and HNMG23-HNMG27) am- plified with the universal primer pair 27f/1492r (Weisburg et al., 1991), showed a complete identity with those of X. arboricola pv. juglandis (AB558555), X. arboricola (AB558553), X. gardneri (FR749911) and X. campestris (GU596424). Furthermore, the gyrB gene sequences (HQ538517-HQ538526) of the same iso- lates (Parkinson et al., 2007), showed 99-100% identity with those of X. arboricola strains from GenBank, but only 88% iden- tity with references strains of Xcm (HQ538527-HQ538538). This is the first report of a X. arboricola pathovar on mango in China inducing a disease for which we propose the name of “bacterial leaf spot” to distinguish it form the “bacterial black spot” caused by Xcm. Further studies are needed for determining pathovar sta- tus of the strain.