The genomes of pathogen affecting mango (left) and pomegranate have been decoded.© CIRAD & IITK
In what they claim to be the first such reports on plant pathogens from India, scientists have decoded the complete genome sequence of bacteria affecting two important fruits of the country — mango and pomegranate.
The scientists from Chandigarh-based Institute of Microbial Technology (IMTECH), a laboratory of India's Council of Scientific and Industrial Research (CSIR), have announced the fully annotated genome of theXanthomonas pathogens that infect these fruits1, 2. Interestingly, they have found that the genomes of the mango and pomegranate pathovars (highly specialized bacterial strains) are not just closely related to each other but also to that of the citrus pathogen.
The diseases caused by these Xanthomonas pathovars of mango, citrus and pomegranate were first noticed in India. "The striking similarities in the genomes suggest that India may be the probable region of origin and diversification of these fruits pathogens," says says Prabhu B. Patil, who led the IMTECH research.
The researchers mapped numerous genes of virulent and pathogenic potential. They also identified some unique genes and markers that will help in epidemiology and quarantine of these fruit pathogens.
"While a lot of research is done on the genomics and evolution of the citrus canker disease because of its worldwide significance, not much has been done to study mango and pomegranate pathogens, which are particularly devastating for India," Patil says.
India is the largest producer of mango, pomegranate and citrus fruits in the world. However, their production and export is hit by diseases caused by the pathovars of genus Xanthomonas. In mango, the disease is known as bacterial black spot and the causal agent is Xanthomonas citri pv. mangiferaeindicae (Xcm). In citrus, the disease is known as bacterial canker and the causal agent is Xanthomonas axonopodis pv. citri (Xac).
"Both these pathovars are serious problems throughout the world," Patil says.
In pomegranate, the disease is known as bacterial blight or telya (oily spots) and the causal agent is Xanthomonas axonopodis pv. punicae (Xap). The pathogen threatens pomegranate cultivation in India because of its devastating effect on all parts of the plant. Though endemic to India as of now, it is a potential threat to pomegranate crops across the world, Patil contends.
The genome study, the team says, could unlock deeper aspects on the evolutionary history of bacterial phytopathogens of India.
Sharma, V. et al. Genome sequence of Xanthomonas axonopodis pv. punicae, Strain LMG 859. J. Bacteriol. 194, 2395 (2012)
Midha, S. et al. Genome sequence of Xanthomonas citri pv. mangiferaeindicae, Strain LMG 941. J. Bacteriol. 194, 3031 (2012)