Predication of the Effector Proteins Secreted by Fusarium sacchari Using Genomic Analysis and Heterogenous Expression

One of the causative agents of pokkah boeng disease (PBD), which affects sugarcane crops globally, is the fungus Fusarium sacchari. These fungal infections reduce sugar quality and yield, resulting in severe economic losses. Effector proteins play important roles in the interactions between pathogenic fungi and plants. Here, we used bioinformatic prediction approaches to identify 316 candidate secreted effector proteins (CSEPs) in the complete genome of F. sacchari. In total, 95 CSEPs contained known conserved structures, representing 40 superfamilies and 18 domains, while an additional 91 CSEPs contained seven known motifs. Of the 130 CSEPs containing no known domains or motifs, 14 contained one of four novel motifs. A heterogeneous expression system in Nicotiana benthamiana was used to investigate the functions of 163 CSEPs. Seven CSEPs suppressed BAX-triggered programmed cell death in N. benthamiana, while four caused cell death in N. benthamiana. The expression profiles of these eleven CSEPs during F. sacchari infection suggested that they may be involved in sugarcane-F. sacchari interaction. Our results establish a basis for further studies of the role of effector molecules in pathogen–sugarcane interactions, and provide a framework for future predictions of pathogen effector molecules.

Óleo fixo de Annona coriacea Mart. (Annonaceae) e suas atividades anticolinesterásica, antimicrobiana e antifúngica

Este estudo avaliou as atividades anticolinesterásica, antimicrobiana e fungicida do óleo fixo das sementes de araticum (Annona coriacea Mart., família Annonaceae), obtido com etanol como solvente extrator. O óleo fixo foi testado in vitro contra a enzima acetilcolina, cepas bacterianas gram-positivas (Staphylococcus aureus e S. epidermides) e gram-negativas (Escherichia coli e Pseudomonas aeruginosa), e fungos (Candida albicans, C. krusei, Neoscytalidium dimidiatum e Fusarium sacchari). O óleo fixo mostrou-se inibidor da enzima acetilcolinesterase, com inibição variando de 37 a 84%. Foi inativo contra bactérias gram-positivas, gram-negativas e fungos, com MIC ≥1024, através do ensaio antimicrobiano. Permitiu controles de crescimento micelial de N. dimidiatum nas cinco doses testadas (0.1, 0.5, 1.0, 2.0 e 3.0 µL mL-1). Não foi observado controle significativo contra F. sacchari, as doses 1, 2 e 3 (0.1, 0.5 e 1.0 µL mL-1) apresentaram porcentagens baixas de inibição, enquanto as doses 4 e 5 apresentaram controle, entretanto, o mesmo não diferiu do crescimento micelial no tratamento controle com meio de cultura. Pode-se concluir que o óleo fixo das sementes de araticum é um forte candidato ao desenvolvimento de fitofármacos à base de A. coriacea contra fungos patogênicos.

First report of Fusarium sacchari causing sugarcane wilt in Bangladesh

Wilt is one of the destructive fungal diseases of sugarcane (Saccharum officinarum L.) affecting sugarcane production in many sugarcane growing regions including Bangladesh. In July 2018, sugarcane plants showing wilting symptom including withered, dried leaves and shriveling stalks with brown to pinkish discoloration in internal tissues (Viswanathan, 2013) were collected from sugarcane field from Gazipur district (23°54′41″ N, 90°23′20″ E) of Bangladesh. Average disease incidence was 17% in 60 ha of sugarcane fields that were sampled for diseased plants with visible symptoms. Ten infected stalks (30cm) were collected from five severely infected fields. The stalks were surface sterilized with 70% ethanol for 1 minute followed by 0.2% sodium hypochlorite for 3 minutes and then rinsed three times with distilled water. Small pieces (2mm×2mm) of the inner discolored tissue were cut with a strile scalpel and placed on half strength Potato Dextrose Agar (PDA) medium followed by incubation for 7 days at 25 °C. A total of ten isolates were recovered from the infected sugarcane stalks and were purified by single spore culture method. Isolates produced floccose and cottony colony with white mycelia and dark violet pigmentation on the lower surface of the PDA plate. Microconidia were oval, generally, without septation measuring 5-9.6 µm length and 1.8-3.7 µm width in size (Appendix 1). Macro conidia were not found on the PDA medium. Conidiophores produced mono- or poly-phialides and conidia were arranged in a false head on conidiophore which is consistent with Fusarium sacchari (Duan et al. 2019). For molecular identification, DNA was extracted from two representative isolates BTFSS1 and BTFSS6. The internal transcribed spacer (ITS) region, translation elongation factor 1-α (TEF-1α) gene and RNA polymerase II (RPB2) genes were amplified using primers ITS1/ITS4, EF1α-F EF1α-R and 5F2/11aR, respectively (Appendix 2). Obtained ITS sequences (GenBank accession nos. MT176492.1 and MT177209.1) showed 99.8% similarity with the sequences from F. sacchari strain olowEKT1 (MK072727.1). Sequence identity of TEF-1α (GenBank accession nos. MW558264.1 and MW507839.1) was 99.36% with the sequence of F. sacchari strain FF031 (MK152501.1) and RPB2 (GenBank accession nos. MW558265.1 and MW507840.1) was 99.42% with the sequence of F. sacchari strain FF001 (MK152508.1), respectively. The isolates BTFSS1 and BTFSS6 were identified as F. sacchari based on the sequences alignment of ITS, TEF-1α and RPB2 and onolecular phylogenetic analyses by maximum likelihood tree method. To confirm the pathogen as a causal agent of wilt of sugarcane, pathogenicity tests were conducted in sugarcane plants by the plug method described by Viswanathan et al. (2011). Ten plants (variety BSRI Akh 42) were inoculated with 1 × 105 conidia mL−1 suspension of the isolate BTFSS1. A borehole was made on the third or fourth internode from the base of the sugarcane plant in where the conidial suspension was placed and the bore place was sealed with cane tissues. Control plants were inoculated with deionized distilled water. All canes were cuts longitudinally to evaluate the disease symptoms at fifteen and thirty days after inoculation. Inoculated stalks exhibited tissue discoloration that were similar to those observed in infected sugarcane field, whereas the control remained unaffected (Appendix 1). Pathogens were re-isolated from the artificially inoculated cane and characterized morphologically. Sugarcane is the second important cash crop and the only source of white sugar in Bangladesh (Rahman et al. 2016). Our report for the first time confirmed that F. sacchari is the causal pathogen of sugarcane wilt in Bangladesh. This report has significance to develop suitable management practices to control the pathogen in sugarcane field.

Fusarochromene, a novel tryptophan-derived metabolite from Fusarium sacchari

Fusarochromene and the fusarochromanone mycotoxins are derived via oxidative cleavage of the aromatic amino acid tryptophan.

Levaduras aisladas de mieles como antagonistas de mohos patógenos de cultivos

Se buscó el aislamiento de levaduras de muestras de miel de la Provincia de Jujuy, Argentina, con el objetivo de utilizarlas in vitro como antagonistas de mohos patógenos pre- y poscosecha, de diferentes cultivos de interés, como, cítricos, maíz, maní y caña de azúcar. Se utilizó miel, ya que la misma puede actuar como medio selectivo de cepas inocuas y tolerantes a distintos estrés abióticos, como bajo pH, elevada presión osmótica, presencia de fitoquímicos, entre otros. Se logró aislar un total de 15 levaduras de 25 muestras de mieles. Las levaduras fueron identificadas como: Candida parapsilosis, Zygosaccharomyces baili, Zygosaccharomyces mellis, Zygosaccharomyces rouxii, Tausonia pullulans, Lachancea thermotolerans, Lachancea fermentati, Torulaspora delbrueckii y Saccharomyces cerevisiae. Todos los géneros se encontraron descriptos como presentes en la miel, provenientes, ya sea, de fuentes primarias de contaminación o del ambiente circundante. De los aislamientos obtenidos se probó el antagonismo in vitro, por disminución del crecimiento micelial de los mohos: Penicillium italicum, P. ulaiense, Aspergillus parasiticus y Fusarium sacchari. Lachancea thermotolerans, fue el único aislamiento que presentó antagonismo hacia todos los mohos ensayados. Candida parapsilosis manifestó antagonismo hacia P. italicum; Lachancea fermentati hacia P. ulaiense; Z. mellis frente P. ulaiense y uno de los aislamientos de T. delbrueckii frente a P. italicum y P. ulaiense. Se podrían utilizar las levaduras antagonistas en futuros ensayos in vivo, en vistas al diseño de un biofungicida activo contra mohos patógenos de cultivos, en la etapa de producción a campo o durante el almacenamiento.