Pokkah boeng disease caused by the Fusarium species complex results in significant yield losses in sugarcane. Thus, the rapid and accurate detection and identification of the pathogen is urgently required to manage and prevent the spreading of sugarcane pokkah boeng. A total of 101 isolates were recovered from the pokkah boeng samples collected from five major sugarcane production areas in China throughout 2012 and 2013. The causal pathogen was identified by morphological observation, pathogenicity test, and phylogenetic analysis based on the fungus-conserved rDNA-ITS. Species-specific TaqMan real-time PCR and conventional PCR methods were developed for rapid and accurate detection of the causal agent of sugarcane pokkah boeng. The specificity and sensitivity of PCR assay were also evaluated on a total of 84 isolates of Fusarium from China and several isolates from other fungal pathogens of Sporisorium scitamineum and Phoma sp. and sugarcane endophyte of Acremonium sp. Two Fusarium species (F. verticillioides and F. proliferatum) that caused sugarcane pokahh boeng were identified by morphological observation, pathogenicity test, and phylogenetic analysis. Species-specific TaqMan PCR and conventional PCR were designed and optimized to target their rDNA-ITS regions. The sensitivity of the TaqMan PCR was approximately 10 pg of fungal DNA input, which was 1,000-fold over conventional PCR, and successfully detected pokkah boeng in the field-grown sugarcane. This study was the first to identify two species, F. verticillioides and F. proliferatum, that were causal pathogens of sugarcane pokkah boeng in China. It also described the development of a species-specific PCR assay to detect and confirm these pathogens in sugarcane plants from mainland China. This method will be very useful for a broad range of research endeavors as well as the regulatory response and management of sugarcane pokkah boeng.

Pokkah boeng, caused by Fusarium verticillioides, is a serious disease in sugarcane industry. The disease severity is related to the sugarcane genotype as well as environmental considerations, such as nitrogen application. The impact of the nitrogen source (ammonium sulfate, urea, or sodium nitrate) on sugarcane pokkah boeng disease and its pathogen was investigated in planta and fungal growth and sporulation production was measured in vitro. The results showed that ammonium and nitrate were beneficial to fungal mycelium growth, cell densities and sporulation, which enhanced the disease symptoms of sugarcane pokkah boeng compared to urea fertilization. A total of 1,779 transcripts out of 13,999 annotated genes identified from global transcriptomic analysis were differentially expressed in F. verticillioides CNO-1 grown in the different sources of nitrogen. These were found to be involved in nitrogen metabolism, transport and assimilation. Many of these genes were also associated with pathogenicity based on the PHI-base database. Several transcription factors were found to be associated with specific biological processes related to nitrogen utilization. Our results further demonstrated that nitrogen availability might play an important role in disease development by increasing fungal cell growth as well as influencing the expression of genes required for successful pathogenesis.

In the South China Sea, coastal eutrophication in the Beibu Gulf has seriously threatened reef habitats by subjecting corals to chronic physiological stress. To determine how coral holobionts may tolerate such conditions, we examined the transcriptomes of healthy colonies of the galaxy coral Galaxea fascicularis and its endosymbiont Symbiodinium from two reef sites experiencing pristine or eutrophied nutrient regimes. We identified 236 and 205 genes that were differentially expressed in eutrophied hosts and symbionts, respectively. Both gene sets included pathways related to stress responses and metabolic interactions. An analysis of genes originating from each partner revealed striking metabolic integration with respect to vitamins, cofactors, amino acids, fatty acids, and secondary metabolite biosynthesis. The expression levels of these genes supported the existence of a continuum of mutualism in this coral-algal symbiosis. Additionally, large sets of transcription factors, cell signal transduction molecules, biomineralization components, and galaxin-related proteins were expanded in G. fascicularis relative to other coral species.

Sugarcane twisted leaf disease, caused by Phoma sp., was first reported in Guangxi, China, in 2012, when more than 5% of sugarcane was infected in the field. Three single-spore isolates were recovered from symptomatic leaves. Sequences from five fungal loci, 28S nrDNA (LSU), 18S nrDNA (SSU), the internal transcribed spacer regions 1 and 2 and 5.8S nrDNA (ITS), β-tubulin (TUB), and the translation elongation factor alpha (TEF-α) were amplified from the disease-associated isolates. The twisted leaf disease pathogen was identified and formally described as Phoma sorghina var. saccharum through phylogenetic analyses, morphological observations, and the pathogenicity of the isolates on sugarcane. P. sorghina var. saccharum can be differentiated from related species based on the morphology of pycnidia and chlamydospores that formed regular, glabrous, papillate ostioles. Chlamydospore-anamorph was unicellular, botryoid-alternarioid shape, as well as the binucleate, frequently branched hyphae. We also showed that mycelial growth of P. sorghina var. saccharum was optimal at pH 4.0 and 20 to 25°C. Additionally, among 13 chemical compounds tested, carbendazim was found to be the most effective in suppressing the radial growth of the fungus. Mycelial growth in vitro was completely inhibited at concentrations of 100 and 50 ppm, and 87.6% of mycelial growth was inhibited at 10 ppm. Carbendazim is therefore a potentially effective fungicide to control this disease in China.

Water hyacinth (Eichhornia crassipes), a worst invasive aquatic weed has been caused the widespread problems for the water bodies and water resources, particularly the case in China. Plant pathogens are a promising alternative as biocontrol agents (Dagno et al. 2011), but success in this strategy will require the selection of some highly virulent pathogen strains. In September 2020, irregular necrotic lesions on leaves, stems, as well as crown and petiole rots symptoms, occurred on water hyacinth, in Minjiang and Xiyuanjiang watershed, in Fuzhou, China. Fragments from symptomatic leaf tissue (5x5mm) were superficially disinfected in 0.1% MgCl2 solution for 30 s, followed by rinsing three times in sterile water, placed on potato dextrose agar (PDA), and then incubated in darkness at 28°C for 5 days. Two fungal isolates (F3 and F11) were recovered and obtained pure cultures from the affected leaves and deposited in the Institute of Oceanography, Minjiang University. The colonies were stale, with felted, dense, pale grey aerial mycelium, scattered dark based acervuli with orange conidial masses near centre; in reverse side pinkish orange with patches of grey pigment near centre. The hyphae were septate, branched, and 2 to 6 µm in width. Appressoria were not observed. Conidiogenous cells were 20-24 × 3.5-4.5 µm, cylindric to flask-shaped, towards margin the conidiophores with a much looser structure, conidiogenous loci at apex and often also at septa. Asci were 60-80 × 15-20 µm, cylindric to subfusoid, 8-spored. Ascospores were 17-23 × 4-6 µm, gently curved, tapering to quite narrow, rounded ends. Perithecia mature after about 15 days, and were dark brown, subglobose, and 50-150 μm in diameter, and with scattered, dark brown setae about 50-80 µm long. Conidia were 15-25 × 4.5-6 μm, unicellular, colorless, and cylindrical to fusiform. Genomic DNA from two isolates was extracted with a modified DNA Midi Kit (TIANGEN, Inc., Beijing, China), and amplified using ITS4/ITS1F, CL1/CL2A, CHS-79F/CHS-345R, T1/T2 and GDF/GDR primers by PCR (Weir et al. 2012; White et al. 1990). Sequences of F3 and F11 were submitted to GenBank (accession no. ITS, MW307302, MW307303; CAL, MW303427, MW303429; CHS-1, MW303428, MW303430; TUB, MW531006, MW531007; GADPH, MW531008, MW531009). A phylogenetic tree using the maximum likelihood methods and including ITS-CHS-CAL-TUB-GADPH concatenated sequences from Colletotrichum gloeosporioides complex was obtained (Cai et al. 2009; Damm et al. 2018; Weir et al. 2012). Phylogenetic analyses revealed that isolate F3 and F11 were grouped into the clade C. fructicola. To test Koch's postulates, conidial suspensions (107 CFU/ml) of the isolate F3 and F11 were micro-injected into 20 water hyacinth seedlings per isolate. Another 20 seedlings were injected with water without conidia as control. Inoculated plants were kept in 50-liter plastic tanks, and maintained in a greenhouse at room temperature (19-24ºC) for two weeks. The Koch's test was conducted twice. After 10 days, typical anthracnose symptoms similar to the field appeared on the inoculated leaves, while the control leaves remained asymptomatic. The C. fructicola was re-isolated and identified by microscopy, PCR and sequencing, but not on non-inoculated controls. Anthracnose disease caused by C. fructicola has been reported affecting numerous plants worldwide, including cotton, coffea, grape, citrus, ect (Guarnaccia et al. 2017). However, to our knowledge, this is the first report of C. fructicola causing anthracnose on water hyacinth in China. Further studies for the efficacy of C. fructicola and/or of the genus Colletotrichum as biocontrol agent for water hyacinth or another aquatic plant are required (Ding et al. 2007; Dagno et al. 2012).