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Citrus melanose consists of a series of plant diseases caused by the fungal species of the genus Diaporthe. It has been reported with over 30 Diaporthe species on citrus, including several important fungal pathogens, endophytes, saprophytes, and also latent fungal pathogens with an endophytic/saprophytic lifestyle. Among them, the disease symptoms caused by Diaporthe citri are complex, and the black spots and sand skin symptoms produced on fruits and leaves are the most serious harm to citrus. Currently, the primers and methods for the detection of D. citri have been constructed, and are supposed to be used in field monitor of the dynamics of the pathogen and the epidemiology of the caused diseases. In the orchard, the infection and outbreak of melanose is highly correlated to the orchard damage by natural disasters and continuous rainfalls, the main disease control strategy should be the combination method of agricultural control, physical control, and chemical control.For the agricultural control, the dead woods, twigs, and leaves should be cleared to reduce the formation of infection sources; for the physical control, it is important to avoid plant wounds by cold and sunburn, and the conidia spread by rains; for the chemical control, the usage of fungicides should be protective to the plant wounds, and also over the period of rainfalls. In addition, the research of the biological control of citrus melanose is still in its infancy, several studies have isolated different antagonistic microorganisms and tested their effects on the control of citrus melanose, which suggest their promising roles as supplementary fungicides. This review summarized the major research progresses of citrus melanose at home and abroad, and aimed to offer some insights to the control of the disease.

Plant disease is an important factor that affects the plant microbiome. However, for many plant–pathogen–microbiome interactions, the influences are unknown. Citrus, comprising abundant varieties of mandarin, sweet orange, pomelo, and lemon, is widely cultivated in different production areas in China. Most of these varieties are vulnerable to citrus canker, which is caused by Xanthomonas spp. In this study, asymptomatic and cankered leaves from asymptomatic and canker-infected trees, respectively, were collected from 17 orchards in six citrus production areas and their endophytic microbiomes were compared. The effects of canker on the microbial community richness and diversity were dependent on whether the interaction type was intrakingdom (for bacteria, positive) and interkingdom (for fungi, negative), respectively. The negative effects of canker on the fungal communities might be affected by the strong correlation between Xanthomonas and Fusarium/Gibberella species. The occurrence of canker significantly affected the composition and structure of both the endophytic fungal and bacterial communities, and altered the dominant genera of each community. In addition, canker occurrence intensified the cross-kingdom microbial interaction network, in which species of Enterobacter, Xanthomonas, Pseudomonas, and Pantoea were detected with increased roles in the network and responsible for the predominant functional genes involved in nutritional metabolism, the bacterial secretion system, and biotin metabolism. The results provide insights into the responses of the endophytic microbiome to citrus canker disease.

Abstract Background Organic mulch is an important management practice in agricultural production to improve soil quality, control crop pests and diseases and increase the biodiversity of soil microecosystem. However, the information about soil microbial diversity and composition in litchi plantation response to organic mulch and its attribution to litchi downy blight severity was limited. This study aimed to investigate the effect of organic mulch on litchi downy blight, and evaluate the biodiversity and antimicrobial potential of soil microbial community of litchi plantation soils under organic mulch. Results Organic mulch could significantly suppress the disease incidence in the litchi plantation, and with a reduction of 37.74% to 85.66%. As a result of high-throughput 16S rRNA and ITS rDNA gene illumine sequencing, significantly higher bacterial and fungal community diversity indexes were found in organic mulch soils, the relative abundance of norank f norank o Vicinamibacterales, norank f Vicinamibacteraceae, norank f Xanthobacteraceae, Unclassified c sordariomycetes, Aspergillus and Thermomyces were significant more than that in control soils. Isolation and analysis of antagonistic microorganism showed that 29 antagonistic bacteria strains and 37 antagonistic fungi strains were unique for mulching soils. Conclusions Thus, we believe that organic mulch has a positive regulatory effect on the litchi downy blight and the soil microbial communities, and so, is more suitable for litchi plantation.

【Objective】The study was conducted to identify the pathogen causing anthracnose of Chrysanthemum in Huaiji of Guangdong province, and to screen the best control agents in the field in order to provide guidance for the prevention and control of Chrysanthemum anthracnose.【Method】Diseased samples (flowers and leaves) of Chrysanthemum with anthracnose symptoms collected from Huaiji of Guangdong were isolated and cultured conventionally. Fungal strains Cg1-1, Cg1-2 and Cg1-3 were isolated and obtained. The pathogenicity of above strains were determined by the Koch's postulates with in vivo and in vitro inoculation of conidial suspension on plants of Chrysanthemum. The spores sizes and myelium morphologies of Cg1-1, Cg1-2 and Cg1-3 were observed under microscope and polygene molecular identification was conducted with ribosomal transcription spacer (ITS), large subunit(LSU)、Chitin synthase (CHS1) and actin (ACT). Finally, Mega7.0.18 was used to construct the phylogenetic tree of Cg1-1, Cg1-2 and Cg1-3 with the maximum natural method. Difenoconazole, Prochloraz, 30% Thifluzamide (Liangzun), 430 g/L Tebuconazole (Cuijian) and 40% Thifluzamide·Trifloxystrobin (Runxiu) were used to control Chrysanthemum anthracnose in the field.【Result】Through the analysis of the biological characteristics of pathogen and the identification of polygene molecular biology, the anthracnose pathogen on Chrysanthemum in Huaiji of Guangdong Province is Colletotrichum gloeosporioides. The field efficacy test results showed that 1 500 times Difenoconazole and 1 500 times Prochloraz has the best control effects on the disease in the field. Attention should be paid to effective application of agents after the rain and in the rapid growing season of Chrysanthemum.【Conclusion】C. gloeosporioides is the causative agent of anthracnose on Chrysanthemum in Huaiji of Guangdong. 1 500 times Difenoconazole and 1 500 times Prochloraz can be used as recommended agents for field control.

Bacteria, inhabiting around and in plant roots, confer many beneficial traits to promote plant growth and health. The secretion of root exudates modulates the nutritional state of the rhizosphere and root area, further selecting specific bacteria taxa and shaping the bacteria communities. Many studies of the rhizosphere effects have demonstrated that selection by the plant rhizosphere consistently enriches a set of bacteria taxa, and this is conserved across different plant species. Root selection effects are considered to be stronger than the rhizosphere selection effects, yet studies are limited. Here, we focus on the root selection effects across a group of 11 stress-resistant plant species. We found that the root selection consistently reduced the alpha diversity (represented by total number of observed species, Shannon’s diversity, and phylogenetic diversity) and altered the structure and composition of bacteria communities. Furthermore, root selection tended to enrich for clusters of bacteria genera including Pantoea, Akkermansia, Blautia, Acinetobacter, Burkholderia-Paraburkholderia, Novosphingobium, Massilia, Pseudomonas, Chryseobacterium, and Stenotrophomonas. Our study offers some basic knowledge for understanding the microbial ecology of the plant root, and suggests that several bacteria genera are of interest for future studies.

Fusarium species have been identified as pathogens causing many different plant diseases, and here we report an emerging banana leaf blight (BLB) caused by F. sacchari (Fs) discovered in Guangdong, China. From the symptomatic tissues collected in the field, a fungal isolate was obtained, which induced similar symptoms on healthy banana seedlings after inoculation. Koch’s postulates were fulfilled after the re-isolation of the pathogen. Phylogenetic analysis on two gene segments and the whole genome sequence identified the pathogen belonging to Fs and named as Fs str. FS66. A 45.74 Mb genome of FS66 was acquired through de novo assembly using long-read sequencing data, and its contig N50 (1.97 Mb) is more than 10-fold larger than the previously available genome in the species. Based on transcriptome sequencing and ab initio gene annotation, a total of 14,486 protein-encoding genes and 418 non-coding RNAs were predicted. A total of 48 metabolite biosynthetic gene clusters including the fusaric acid biosynthesis gene cluster were predicted in silico in the FS66 genome. Comparison between FS66 and other 11 Fusarium genomes identified tens to hundreds of genes specifically gained and lost in FS66, including some previously correlated with Fusarium pathogenicity. The FS66 genome also harbors widespread gene transfer on the core chromosomes putatively from F. oxysporum species complex (FOSC), including 30 involved in Fusarium pathogenicity/virulence. This study not only reports the BLB caused by Fs, but also provides important information and clues for further understanding of the genome evolution among pathogenic Fusarium species.

The most serious citrus postharvest diseases are citrus green mould caused by Penicillium digitatum and citrus blue mould caused by Penicillium italicum. Marine microorganisms have become a new measure in the control of these diseases. In this study, we isolated 56 marine actinomycetes, and strain AM-4 isolated from Drupa granulata exhibited the strongest antagonistic activity against P. digitatum. Molecular, morphological, cultural and physio-biochemical analysis identified strain AM-4 as Streptomyces chumphonensis. Strain AM-4 also exhibited antagonistic activity against 11 other phytopathogens, with an inhibition zone width ranging from 0.65 ± 0.04 to 2.35 ± 0.02 cm. The mycelial growth inhibition rates of the fermentation liquid of strain AM-4 against P. digitatum and P. italicum were 66.23% and 61.42%, respectively, and the conidial germination inhibition rates were 65.77% and 62.13%, respectively. The relative control efficacy of the gradient-diluted fermentation extracts of strain AM-4 against citrus green mould caused by P. digitatum ranged from 77.95% to 92.91% at 5 days post inoculation and 56.30% to 87.22% 10 days after inoculation. The relative control efficacy of the gradient diluted fermentation extracts of strain AM-4 against citrus blue mould caused by P. italicum ranged from 61.32% to 84.91% 5 days after inoculation and from 51.34% to 80.92% 10 days after inoculation. The relative control efficacy of the fermentation extracts of strain AM-4 was even better than prochloraz against citrus green mould caused by prochloraz-resistant P. digitatum. Therefore, as a biological control strain, AM-4 has a good prospect for development and utilization potential.

In this study, two polyclonal antibodies were produced against the Omp protein of 'Candidatus Liberibacter asiaticus'. First, omp genes were sequenced to exhibit 99.9% identity among 137 isolates collected from different geographical origins. Then, two peptides containing the hydrophobic polypeptide-transport-associated (POTRA) domain and ßbarrel domain, respectively, were identified on Omp protein. After that, these two peptides were overexpressed in Escherichia coli and purified by affinity chromatography to immunize the white rabbits. Finally, the antiserum was purified by affinity chromatography. The two Omp antibodies gave positive results (0.454 to 0.633, 1:1,600 dilution) in enzyme-linked immunosorbent assay against 'Ca. L. asiaticus'- infected samples collected from different geographical origins but revealed negative results against other pathogen-infected, nutrient-deficient and healthy samples. The antibody against the POTRA domain of Omp protein could detect 'Ca. L. asiaticus' in 45.7% of the symptomatic samples compared with a 56.2% detection rate with a polymerase chain reaction assay. These new antibodies will provide a very useful supplement to the current approaches to 'Ca. L. asiaticus' detection and also provide powerful research tools for tracking distribution of this pathogen in vivo. [ABSTRACT FROM AUTHOR]