Genetic Diversity and Streptomycin Sensitivity in Xanthomonas axonopodis pv. punicae Causing Oily Spot Disease in Pomegranates

Xanthomonas axonopodis pv. punicae (Xap) causes bacterial blight disease in pomegranates, often leading to 60–80% economic loss. In absence of a suitable Xap-resistant variety, the near-monoculture of the susceptible variety, Bhagwa, has aggravated the problem further. In recent times, Xap has sprea...

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Bibliographic Details
Published inHorticulturae Vol. 8; no. 5; p. 441
Main Authors Sharma, Jyotsana, Manjunatha, Nanjundappa, Pokhare, Somnath S., Patil, Prakash G., Agarrwal, Ruchi, Chakranarayan, Mansi G., Aralimar, Anita, Devagire, Priya, Marathe, Rajiv A.
Format Journal Article
LanguageEnglish
Published Basel MDPI AG 01.05.2022
Subjects
Adaptability
antibiotic resistance genes
Antibiotics
Bacteria
bacterial blight
Binding sites
Blight
Economic impact
Fruits
Gene transfer
Genes
Genetic diversity
Genetic variability
Horizontal transfer
Metabolism
Monoculture
Mutation
Pathogenicity
Pathogens
Point mutation
pomegranate
Pomegranates
RpsL gene
Sensitivity analysis
Streptomycin
Sulfates
Xanthomonas axonopodis
Xanthomonas axonopodis pv. punicae
India
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Summary:Xanthomonas axonopodis pv. punicae (Xap) causes bacterial blight disease in pomegranates, often leading to 60–80% economic loss. In absence of a suitable Xap-resistant variety, the near-monoculture of the susceptible variety, Bhagwa, has aggravated the problem further. In recent times, Xap has spread to different geographical regions, indicating the wide adaptability of the pathogen. Moreover, lower sensitivity of Xap towards streptocycline containing streptomycin sulphate and tetracycline sulphate (9:1) under field conditions is frequently reported. Therefore, the current study was undertaken to assess the genetic variability of Xap isolates using SSR markers, their in vitro sensitivity towards streptomycin was evaluated, and the probable molecular basis of acquired resistance was studied. Two highly diverse isolates showed extreme differences in their pathogenicity, indicating the highly evolving nature of the pathogen. Moreover, all the isolates showed less than 50% growth inhibition on media containing 1500 µg/mL streptomycin, indicating a lower level of antibiotic sensitivity. On the molecular level, 90% of the isolates showed the presence of strA-strB genes involved in streptomycin metabolism. Additionally, G to A transitions were observed in the rpsL gene in some of the isolates. The molecular data suggest that horizontal gene transfer (strAB) and/or spontaneous gene mutation (in rpsL) could be responsible for the observed lower sensitivity of Xap towards streptomycin.
ISSN:2311-7524
2311-7524
DOI:10.3390/horticulturae8050441