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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #326926
Title: Zinc treatment increases the titre of 'Candidatus Liberibacter asiaticus' in huanglongbing-affected citrus plants while affecting the bacterial microbiomes

Author
item ZHANG, MUQING - University Of Florida
item GUO, YING - University Of Florida
item POWELL, CHARLES - University Of Florida
item Doud, Melissa
item YANG, CHUANYU - University Of Florida
item ZHOU, HUI - Guangxi University
item Duan, Ping

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2016
Publication Date: 6/15/2016
Citation: Zhang, M., Guo, Y., Powell, C., Doud, M.S., Yang, C., Zhou, H., Duan, Y. 2016. Zinc treatment increases the titre of 'Candidatus Liberibacter asiaticus' in huanglongbing-affected citrus plants while affecting the bacterial microbiomes. Journal of Applied Microbiology. doi:10.1111/jam.13102.

Interpretive Summary: Huanglongbing (HLB), the most devastating citrus disease worldwide and the pathogen in the USA is Candidatus Liberibacter asiaticus (Las). The bacterial microbiome of citrus after Las-infection and treatments with zinc was characterized using the Phylochip™ G3 array. This microarray assesses microbial community structure based on amplified 16S rRNA gene sequences. The results revealed that 5,475 of over 50,000 known OTUs (Operational Taxonomic Units) in 52 phyla were detected in the citrus leaf midribs. The OTUs are entities whose affinities are studied by numerical taxonomy. Depending on the level and the type of investigation an OTU may be of any taxonomic rank or an individual organism. Four phyla were dominant, Proteobacteria (25.8-60.2 %), Firmicutes (15.7~26.6 %), Actinobacteria (11.8-22.4 %), and Bacteroidetes (1.6-9.7 %). The OTU representing ‘Candidatus Liberibacter’ had a higher titer in infected plants treated with higher concentration at 250 mg/L than the controls. This indicated that zinc promoted Las bacterial multiplication in the infected plants. The PhyloChip array also demonstrated that more OTUs, at a higher abundance, were detected in the diseased and healthy plants with zinc treatments. These results provide new insights into microbial communities that may be associated with the progression of HLB and the beneficial effects of zinc on the HLB bacteria.

Technical Abstract: The bacterial microbiomes of citrus plants in response to ‘Candidatus Liberibacter asiaticus’ (Las)-infection and zinc treatments were deciphered by Phylochip-based metagenomics. The results indicated that 5,475 of over 50,000 known Operational Taxonomic Units (OTUs) in 52 phyla were detected in citrus leaf midribs using the PhyloChipTM G3 array, of which Proteobacteria was the most abundant (25.8-60.2 %), followed by Firmicutes (15.7~26.6 %), Actinobacteria (11.8-22.4 %) and Bacteroidetes (1.6-9.7 %). More OTUs were detected after zinc treatment (3,980 and 2,642 in the diseased and healthy plants, respectively), especially in the phyla of Proteobacteria, while higher percentages of Firmicutes and Actinobacteria were present in the samples without zinc treatment. Pairwise comparisons indicated that the OTUs from Stenotrophomonas maltophilia had higher HybScores detected only in the zinc treatment. With zinc treatments, the abundant OTUs present in the diseased plants included 16 OTUs of Burkholderia, 5 OTUs of Erwinia, 96 OTUs from Acinetobacter, 17 OTUs of Paenibacillus and 11 OTUs of Brevibacillus, and 114 OTUs of 4 genera in the family of Sphingomonadaceae., which may associate with zinc solubilization, siderophore production, suppression of disease-causing microbes and promotion of nutrient availability and assimilation. Only zinc-sensitive Staphylococcaceae had higher OTU’s in the diseased plants without Zn treatment. Supplemental zinc, especially in the higher concentrations of 250 mg/L, promoted Las bacterial multiplication and increased Las titers. These results provide new insights into microbial communities that may be associated with the progression of citrus huanglongbing (HLB) and the potential effects of zinc on the disease and microbial ecology.