First report of bacterial leaf spot of mango caused by a Xanthomonas arboricola pathovar in China.
A disease of mango observed in 2009-2010, in Hainan and Guangxi (China), is characterized by small water-soaked spots on the leaves turning with age into angular, 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 differed from those of mango bacterial black spot caused by X. campestris pv. mangiferaeindicae (Xcm). Purified bacterial colonies appeared yellow, slimy and convex on YDCA medium, and induced hypersensitive responses on tobacco. The field syndrome was reproduced on inoculated mangoes and the same bacterium was reisolated from symptomatic, but not from control leaves, which remained symptomless. The sequences of 16S rDNA gene fragment (ca.1.4 kb) (JF803830-JF803839) of 10 isolates (GXMG2, GXMG5, GXMG8, GXMG9, GXMG10 and HNMG23-HNMG27) amplified with the universal primer pair 27f/1492r, 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 isolates showed 99-100% identity with those of X. arboricola strains from GenBank, but only 88% identity with references strains of Xcm (HQ538527-HQ538538). This is thought to be the first report of a X. arboricola pathovar on mango in China.