Impacts of antibiotic application on citrus plants and rhizosphere bacterial communities.

Antibiotics are used to control certain bacterial diseases in crops because of their remarkable capacity to treat fatal diseases (McManus, Stockwell, Sundin, & Jones, 2002). Since the 1950s, antibiotics have been used to successfully control a variety of plant diseases, including lethal yellowing in elm and coconut palm trees, fire blight on apples and pears, leaf spot on peaches, tomatoes, and nectarines, "Huanglongbing" on citrus trees (McManus et al., 2002; Yin et al., 2023). However, questions have been expressed about the uptake and translocation of applied antibiotics to the receiving plants and related health risks to humans and plants along with the introduction of antibiotics into plant agriculture. In terms of human and animal health, bacterial resistance has been a significant problem; nevertheless, antibiotic ecotoxicological relevance is hardly understood due to the potential effects of antibiotics on the environment (Rooklidge, 2004).Antibiotics in treating citrus greening disease in Florida is a prevalent agricultural approach, especially when the disease poses a significant risk to crop yields.Citrus greening, or Huanglongbing (HLB), is one of the most harmful citrus diseases in the world, infecting almost all commercial citrus species. Infected trees produce small, asymmetrical, bitter-tasting fruit with tiny, abortive seeds, and they may also have blotchy-mottled or entirely yellow chlorotic leaves that occasionally resemble mineral deficiencies (Folimonova, Svetlana Y. et al. 2009). As the disease progresses, tree growth and fruit yield are significantly reduced, making the orchard economically unviable. The causal agent of HLB in Florida is thought to be Candidatus Liberibacter asiaticus (Clas), which is supported by positive results of polymerase chain reaction (PCR)-based assays of multiple samples collected from various regions throughout the state using Clas-specific oligonucleotide primers and 16S rRNA gene clone library sequencing. It is shown that antibiotics use in plant production impact plant physiology and may negatively affect plant microbiome. The soil microorganisms are essential in various plant processes, such as growth, development, and stress response. Thus, more research is needed to fully understand the specific effects of antibiotics on citrus and tomato plants' physiology and microbiome.To investigate the possible impact of accumulated antibiotics on the citrus plant microbiome, we look at the bacterial and culturable antibiotic-resistant microorganisms in rhizosphere soil. Understanding antibiotic uptake by crops after application and associated risks on plant microbiomes are critical. In this study, oxytetracycline and streptomycin, the two most used antibiotics in agriculture, were applied separately to citrus seedlings via continuous soil drenching to study their influence on the plant microbiome and health. In this study, 250 mg of rhizosphere soils of each sample was used for DNA extraction using a Quick-DNA Fecal or Soil Microbe Miniprep Kit from Zymo Research. After eluting the DNA in the elution buffer supplied by the DNA isolation kit, we stored the DNA until ready to proceed with submission for the 16S rRNA gene amplification. Our findings, showed that both streptomycin and oxytetracycline reduce the bacterial population in rhizosphere soil. The following study was to assess the impacts of the antibiotic affected bacteria on plant nutrition, plant physiology, and plant microbiome recovery.