Three Distinct Species Cause Bacterial Leaf Spots in ‘Ubá’ Mango in Zona da Mata, Minas Gerais, Brazil

ABSTRACT ‘Ubá’ mango is a fruit crop of great value for farmers in the Zona da Mata region of Minas Gerais state, Brazil. Organic farmers from this region recently reported a severe outbreak of foliar black spots of unknown aetiology in orchards of this mango variety, causing significant concern. The objective of this study was to identify the causal agent of the disease by conducting microbial isolations, biochemical and molecular characterizations, multi‐locus sequence analysis and pathogenicity tests. Bacterial isolates displaying orange‐, yellow‐ and cream‐coloured colonies were recovered from diseased leaves collected in the mango orchards. Upon inoculation of healthy mango plants, a representative isolate of each colony colour was able to reproduce the black spot symptoms typical of the disease. Bacterial isolates with the same colony morphology as those recovered from naturally infected plants were reisolated from the inoculated plants, confirming that they are etiological agents of the disease. In a phylogenetic analysis, the cream‐coloured bacterium clustered in the same clade with the Burkholderia contaminans type strain, whereas the yellow‐ and orange‐bacteria formed independent clades within Sphingomonas and Microbacterium , respectively, indicating the identification of new bacterial genomospecies. These results revealed that the leaf spots of mango trees in Ubá have a complex aetiology, represent the first report of the pathogenicity of these three bacterial species towards mango trees and provide crucial information for the development of diagnostic and control methods.