Trichoderma asperellum (NST-009): A Possible Thai Native Antagonistic Fungus for Managing White Root Disease of Rubber Trees (Hevea brasiliensis)

Background: Rigidoporus microporus causes white root disease, which is one of the most harmful diseases in rubber trees in Thailand. The objectives of this study were to determine the efficacy of T. asperellum NST-009 and its antifungal metabolite in inhibiting R. microporus mycelial development and efficacy of T. asperellum NST-009 in controlling white root disease of rubber trees in an open-field house experiment. Methods: Four native strains of T. asperellum from Nakhon Si Thammarat Province and a commercial strain of Thailand were used in this study. This study was conducted at Agricultural Microbial Production and Service Center, Walailak University, Nakhon Si Thammarat, Thailand, during the period 2017-2020. Result: T. asperellum NST-009 significantly inhibited R. microporus mycelial growth by 77.07% in vitro and its antifungal metabolite from the culture filtrate of T. asperellum NST-009 inhibited mycelial growth by 92.31%. T. asperellum NST-009 reduced the disease severity index by 76.38% in the open-field house experiment compared to the inoculated control. Furthermore, T. asperellum NST-009 was found to survive in rhizosphere soil at 4.50 × 105 CFU/g soil and colonized the roots at 100.00%.

Efecto del pH y Sales Inorgánicas en la Degradación de Colorantes Industriales por Pleurotus Djamor

En la presente investigación se planteó el uso de la cepa Pd318 del hongo Pleurotus djamor como agente biorremediador, con el objetivo de evaluar su capacidad para degradar el colorante reactivo azul 19 (A19). Para ello se estudió la influencia que tienen cinco sales inorgánicas en el crecimiento y actividad lignolítica del hongo. Un cribado de sales inorgánicas en placa determinó que las sales CaCl2.2H2O y MnSO4.5H2O tienen mayor influencia en el desarrollo micelial y actividad lignolítica de la cepa. Ensayos de fermentación líquida (FEL) con diferentes combinaciones a distintas concentraciones de las sales de calcio y manganeso permitieron demostrar la capacidad de degradación del colorante azul 19 a los 7 días de fermentación líquida a temperatura ambiente y agitación constante. Los máximos porcentajes de degradación del colorante fueron obtenidos con las combinaciones A1B1 y A2B1 con 43,47% y 41,36%, respectivamente. Se observó que a un pH de 5 unidades se favorece la degradación del colorante. Los estudios en placa señalaron que la adición de sales de calcio y manganeso en 10 días de incubación favorecieron el desarrollo micelial y la actividad lignolítica de Pd318, mientras que en un sistema FEL de 7 días, únicamente la adición de manganeso influye favorablemente a la actividad lignolítica del hongo y en consecuencia a su capacidad de degradación de azul 19. Palabra clave: Colorante azul 19, degradación de colorantes, enzimas lignolíticas, Pleurotus djamor. Abstract In the present investigation, the use of the Pd318 strain of the Pleurotus djamor fungus as a bioremediation agent was proposed, with the aim of evaluating its ability to degrade reactive dye blue 19 (A19). For this, the influence of five inorganic salts on the growth and lignolytic activity of the fungus was studied. A plate screening of inorganic salts determined that the CaCl2.2H2O and MnSO4.5H2O salts have a greater influence on the mycelial development and lignolytic activity of the strain. Liquid fermentation tests (FEL) with different combinations at different concentrations of the calcium and manganese salts allowed to demonstrate the degradation capacity of the blue dye 19, after 7 days of liquid fermentation at room temperature and constant stirring, the maximum degradation percentages of the dye were obtained with the combinations A1B1 and A2B1 with 43.47% and 41.36% respectively. It was observed that at a pH of 5 units the degradation of the dye is favored. The plate studies indicated that the addition of calcium and manganese salts in 10 days of incubation, favored mycelial development and the lignolytic activity of Pd318, while in a 7 day FEL system, only the addition of manganese favorably influenced the lignolytic activity of the fungus and consequently its ability to break down blue 19. Keywords: Blue dye 19, dye degradation, lignolytic enzymes, Pleurotus djamor.

Effect of essential oils on the development of Colletotrichum sp. fungus in fragments of Feijoa sellowiana fruits

The aim of this work was to evaluate the effect of the essential oils of Syzygium aromaticum, Cymbopogon citratus, Eucalyptus citriodora and Rosmarinus officinalis on the mycelial development of the fungus Colletotrichum sp. in fragments of Feijoa sellowiana fruits. The essential oils were incorporated in the PDA (Potato-Dextrose-Agar) medium in the concentrations of 250, 500 and 1000 ppm, 0 ppm (PDA only) (negative control), and fungicide fluazinam 1% (positive control). The area under the mycelial growth curve (AUMGC) and percent inhibition of mycelial growth (PIMG) were calculated. In the second evaluation, fruits fragments bordering the disease symptom were immersed in essential oils aqueous solution of S. aromaticum, C. citratus, and E. citriodora, at the concentration of 5000 ppm, 0 ppm (water only - negative control) and fluazinam 1% (positive control). The immersion times in the treatments were: 2, 4, 8, 12 and 24 hours, with subsequent incubation in Agar-Agar medium at 25°C. This evaluation was performed daily for 15 days, observing the moment of fungal germination through the emission of the mycelium. It was verified from the obtained results that all treatments reduced the fungal growth, and the essential oils of C. citratus and S. aromaticum totally inhibited its growth from the dose 500 and 1000 ppm, respectively. Regarding the test on fruit fragments, the essential oil of S. aromaticum at the immersion times of 12 and 24 hours was effective in inhibiting the fungus until the 15th day of evaluation.

Evaluation of high dilutions extract of pyroligneous on the development of Colletotrichum gloeosporioides

The aim of this research was to evaluate the fungitoxicity of high dilutions of tectonic (Tectona grandis) extract in mycelial growth, sporulation and germination of the fungus Colletotrichum gloeosporioides. In a completely randomized design with six dynamizations of the pyroligneous extract (3, 9, 15, 21, 27 and 33 CH) and three controls (distilled water, mother tincture, 30% hydroalcoholic solution) with four replicates each. All treatments were diluted to 0.1% in BDA medium. Mycelial growth rate index, relative percentage of mycelial development (PRD%), inhibition of sporulation and spore germination (%) were evaluated. The treatments did not differ among them for mycelial growth, percentage of spore germination and IVCM. The PRD and sporulation variables varied according to the dynamization, with a maximum reduction of 7% in PRD (33 CH) and a 70% increase in sporulation (3 and 21 CH). The dynamized pirolenous extract did not present expressive fungitoxicity in the growth, sporulation and germination of C. gloeosporioides.

Effect of light and darkness on the growth and development of downy mildew pathogen Hyaloperonospora arabidopsidis

SummaryDisease development in plants requires a susceptible host, a virulent pathogen, and a favourable environment. Oomycete pathogens cause many important diseases and have evolved sophisticated molecular mechanisms to manipulate their hosts. Day length has been shown to impact plant-oomycete interactions but a need exists for a tractable reference system to understand the mechanistic interplay between light regulation, oomycete pathogen virulence, and plant host immunity. Here we present data demonstrating that light is a critical factor in the interaction between Arabidopsis thaliana and its naturally occurring downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa). We investigated the role of light on spore germination, mycelium development, sporulation and oospore formation of Hpa, along with defence responses in the host. We observed abundant Hpa sporulation on compatible Arabidopsis under day lengths ranging from 10 to 14 hours. Contrastingly, exposure to constant light or constant dark suppressed sporulation. Exposure to constant dark suppressed spore germination, mycelial development and oospore formation. Interestingly, exposure to constant light stimulated spore germination, mycelial development and oospore formation. A biomarker of plant immune system activation was induced under both constant light and constant dark. Altogether, these findings demonstrate that Hpa has the molecular mechanisms to perceive and respond to light and that both the host and pathogen responses are influenced by the light regime. Therefore, this pathosystem can be used for investigations to understand the molecular mechanisms through which oomycete pathogens like Hpa perceive and integrate light signals, and how light influences pathogen virulence and host immunity during their interactions.

Potential of Trichosporon asahii against Alternaria sp. and mechanisms of actions

ABSTRACT Alternaria sp. is a fungus that causes rot in several crops, causing damage to the agricultural production chain. Biological control agents constitute an alternative to reduce the use of pesticides in the crops, a social demand for modern agriculture. The aim of the present study is to demonstrate the antagonistic effect of the yeast Trichosporon asahii (3S44) on the mycelial development of Alternaria sp. and some in vitro mechanisms of action. Trichosporon asahii showed antagonistic activity towards Alternaria sp., presenting mycelial inhibition (57.47%). The assays indicated production of volatile organic compounds (VOCs), competition for nutrients, biofilm formation, production of killer toxins and β-1,3-glucanase as mechanisms of action of T. asahii. Collectively, our results showed the potential of T. asahii to control the mycelial development of Alternaria sp. and some mechanisms of action of this yeast for future biotechnological studies.

Chemical composition and biological activity of the essential oil of the fruits Pimenta dioica against formae speciales of fungus Fusarium oxysporum

We determined the chemical composition and explored the hypothesis that the essential oil of the fruits of Pimenta dioica inhibits the mycelial development of fungi Fusarium oxysporum f. sp. lycopersici, F. oxysporum f. sp. passiflorae, F. subglutinans f. sp. ananas , F. oxysporum f. sp. vasinfectum e F. oxysporum f. sp. Cubense. To do this, we extracted the oil by hydrodistillation, identified its components by gas chromatography coupled to mass spectrometry (GC-MS) and determined the fungal activity against five special forms of Fusarium species. The results showed that the oil had 76.88% of eugenol and inhibited the mycelial development of fungi up to 97.78% in an average of 7.2 days. Therefore, oil is a potential natural fungicide.