Isolation, Antimicrobial Effect and Metabolite Analysis of Bacillus amyloliquefaciens ZJLMBA1908 against Citrus Canker Caused by Xanthomonas citri subsp. citri.

Citrus canker caused by Xanthomonas citri subsp. citri is a devastating bacterial disease with severe implications for the citrus industry. Microorganisms possessing biocontrol capabilities against X. citri subsp. citri offer a highly promising strategy for healthy citrus management. In the present study, a broad-spectrum antagonist strain ZJLMBA1908 with potent antibacterial activity against X. citri subsp. citri was isolated from symptomatic lemon leaves, and identified as Bacillus amyloliquefaciens. Cell-free supernatant (CFS) of strain ZJLMBA1908 also exhibited remarkable antimicrobial activity, especially suppressing the growth of X. citri subsp. citri and Nigrospora oryzae, with inhibition rates of 27.71% and 63.75%, respectively. The antibacterial crude extract (CE) derived from the CFS displayed effective activity against X. citri subsp. citri. A preventive treatment using the CE significantly reduced the severity and incidence of citrus canker in a highly susceptible citrus host. Additionally, the CE maintained activity in the presence of protease and under a wide range of temperature and pH treatments. Applying high-performance liquid chromatography (HPLC) to separate and purify the CE resulted in the discovery of one highly potent anti-X. citri subsp. citri subfraction, namely CE3, which could completely inhibit the growth of X. citri subsp. citri. Liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analysis revealed that CE3 mainly consisted of palmitic acid, surfactin C15, phytosphingosine and dihydrosphingosine. Taken together, the results contribute to the possible biocontrol mechanisms of B. amyloliquefaciens ZJLMBA1908, as well as providing a promising new candidate strain as a biological control agent for controlling citrus canker.

Complete plastome sequence of Ardisia bullata G. H. Huang & G. Hao, an endemic species in Hainan.

Ardisia bullata G. H. Huang & G. Hao is a small shrubs of Primulaceae. It is only distributed in Hainan provinces of China. It is a plant medicinal value. There is no study on the genome of A. bullata so far. Here, we report and characterize the complete plastid genome sequence of A. bullata in an order to provide genomic resources useful for promoting its conservation. The complete chloroplast genome of A. bullata is 160,176 bp in length with a typical quadripartite structure, consisting of a large single-copy region (LSC, 89,710 bp), a single-copy region (SSC, 18,357 bp), and a pair of inverted repeats (IRs, 26,054 bp). There are 133 genes annotated, including 83 unique protein-coding genes, eight unique ribosomal RNA genes, and 37 transfer RNA genes. The overall G/C content in the plastome of A. bullata is 36.0%. The complete plastome sequence of A. bullata will provide a useful resource for the conservation genetics of this species as well as for phylogenetic studies in Apocynaceae.