Molecular based associations of bacterial pathogens with citrus: Implications for toxicology and disease management

Abstract

The losses associated with the bacterial diseases of citrus leaves and fruits have been reported throughout all of Pakistan's citrus-growing regions and a lot of work was done on the morphological characterization of pre and post-harvest pathogens. However, this issue has not been addressed in Khanpur, which is a major citrus-producing city in Pakistan and can help in the economic growth of the country. The citrus fruits in the area under study exhibit disease symptoms during pre and post-harvesting, but the actual disease agents have not yet been identified. The retrospective object of the current research is to study the pathogenic variation along with the investigation of bacterial disease incidence i.e. citrus canker, bacterial spots, & HLB in citrus fruit. During a survey conducted in November 2019 and 2020, bacterial isolates from symptomatic citrus fruits were obtained from randomly chosen orchards in Khanpur.The disease assessment was estimated by determining prevalence, severity, and disease incidence (DI). The bacterial isolates were identified morphologically and further through 16S rRNA gene amplification. The identified species were Pseudomonas syringae, Pseudomonas viridiflava, Serratia marcescens, Xanthomonas axonopodis pv citri, and Candidatus liberibacter. In the pathogenicity test, the Xanthomonas strains responsible for the canker disease caused the most severe disease symptoms. To our knowledge, this is the first report on pathogens of citrus fruits in Khanpur. Given the significant contribution of citrus fruits to household income and foreign exchange in Pakistan, this study illustrates the molecular-based association of bacterial pathogens of citrus and the toxic behavior of pathogens which helps to provide recommendations on genetic testing and to develop management programs for disease management. The molecular identification of citrus pathogens will empower the citrus growers, researchers, and regulatory agencies to make informed decisions that will protect citrus crops, reduce economic losses, and promote sustainable agriculture. It is also likely to play an increasingly vital role in the future of citrus cultivation..