Analysis of Endophytic Bacterial Diversity From Different Dendrobium Stems and Discovery of an Endophyte Produced Dendrobine-Type Sesquiterpenoid Alkaloids

As the unique component of Dendrobium, dendrobine-type sesquiterpenoid alkaloids (DSAs) possess a variety of medicinal properties. It has been well documented that plant endophytes can in vitro synthesize secondary metabolites identical or similar to metabolites produced by their host plants. This study aimed to investigate the composition and distribution of endophytic bacteria of Dendrobium stems by Illumina MiSeq platform sequencing and cultivation-dependent methods and then to assess the potential for endophytic bacteria to produce DSAs. Results indicated that it was necessary to combine both cultivation-dependent and cultivation-independent methods to analyze the community structure of endophytic bacterial in plants comprehensively. The length of the Dendrobium stems influenced the endophytic bacterial community. The diversity and richness of endophytic bacteria in group J10_15cm of stems were the highest, which showed a significant difference from the other stem groups. However, there was no certain connection between the diversity and richness of endophytic bacteria and the content of dendrobine. It was most likely due to the influence of several specific endophytic bacteria genera, such as Sphingomonas and Rhodococcus. Athelia rolfsii, Myrothecium roridum, as pathogenic fungi, and Pectobacterium carotovorum subsp. actinidiae, as pathogenic bacteria of Dendrobium, were used to determine the antimicrobial activities. In these assays, six strains belonging to five genera showed antimicrobial activity against at least two phytopathogens. The strain BL-YJ10_15-29 (Paracoccus pueri THG-N2.35, 98.98%) showed the best antimicrobial activity against the three phytopathogens. In addition, 2 DSAs (6-hydroxydendrobine and nobilonine) were identified in the fermentation supernatant of the strain CM-YJ10_15-44 (Pseudomonas protegens CHA0, 99.24%), whereas the whole-genome analysis results further demonstrated that the precursors of the two DSAs [geranyl-PP and (E, E)-famesyl-PP] were synthesized mainly through the methyl-D-erythritol 4-phosphate pathway in this strain. This study provides new insight into the studies on the biosynthesis of DSAs and provides potential biocontrol bacteria.

Грибковые патогены в листьях нижнего яруса сортов томата Mary Gratefully и Tomiș

Pathogenic fungi are the cause of various diseases of crops. Phytopathogens infect seeds as well as the host-plants in the course of the whole duration of their ontogenesis. Plants are infected when grown in greenhouses or in open fields by a single causal agent or several pathogenic fungi. In current study, a nested PCR protocol was applied for identification of tomatoes’ infection. An infestation with Alternaria spp. and Myrothecium roridum in the lowest leaves on the stem was stated using molecular diagnostics. The ‘Tomis’ and ‘Mary Gratefully’ tomato cultivars were used in current study. Alternaria spp. was iden-tified in each of the samples. The pathogen’s species was defined. Myrothecium roridum infested 10 sam-ples of the ‘Tomis’ genotype and 11 samples of the ‘Mary Gratefully’ genotype of the 12 samples.

Optimization of Culture Conditions for Mycelial Growth and Sporulation of Myrothecium roridum

Culture and nutrition conditions of Myrothecium roridum Tode were optimized by conducting a series of interlined experiments on a growth medium, temperature, pH, and photoperiod. In contrast, relation of culture age with virulence was measured by fungal development on young leaves of bitter gourd. The physiological response was measured on colony radial growth and spore production. Among the six test growth media, i.e., nutrient agar (NA), potato dextrose agar (PDA), Czapek-Dox agar (CDA), glucose agar (GA), malt extract agar (MEA), and bitter gourd agar (BGA), the highest radial growth (77 mm) and the highest number of spores (239 × 106 spores/ml) were observed on PDA. Incubation temperature was evaluated between a range of 15-40 °C, and the highest colony growth (87 mm) was observed at 30 °C, whereas the highest spore production (315 × 106 spores/ml) was at 35 °C. Different pH levels, i.e., 5, 5.5, 6, 6.5, 7, and 7.5, were optimized, and the highest colony growth (87 mm) and spore production (504 × 106 spores/ml) was recorded at pH 5.0. Impact of photoperiod was studied, and the highest mycelial growth (88 mm) and maximum spore production (524 × 106 spores/ml) was observed at 16/8 h alternate light and dark period. It was concluded that the optimum conditions for mycelia growth and spore production was pH 5.0-6.0 and at 30 ± 2 °C in PDA with 16/8 h alternate light and dark photoperiod.

Effect of Cercospora piaropi Tharp and Myrothecium roridum Tode Fries Formulated as Corn Oil Emulsion on Water Hyacinth Shoot Growth under Greenhouse Conditions

A study was done to find out the comparative effect of Cercospora piaropi Tharp and Myrothecium roridum Tode Fries formulated as corn oil emulsion on water hyacinth shoot growth and biomass under greenhouse conditions. The study site was located in Kibos at latitude 0037’S and longitude 37020’E with average temperature of 25 to 300C and 22 to 270C during the day and night respectively, and 60 to 69% relative humidity. Healthy water hyacinth plants were inoculated with the pathogens formulated in corn oil at 1x109, 1x108, 1x107, 1x106 and 1x105spores/ml. The control plants were not inoculated. The experiment was set up in completely randomized design (CRD) with each treatment replicated three times. At weeks 2, 4, and 6 after inoculation, the average shoot length and biomass for the treated basins were separately compared to the average shoot length and biomass of the control plants. Increase in spore density for both pathogens significantly increased relative shoot length and relative biomass. Relative shoot length was 55.07 and 51.93 for C. piaropi and M. roridum respectively at 1x109 spores/ml while relative biomass was 73.53 for C. piaropi and 37.60 at 1x109 spores/ml. Inoculation suppressed shoot elongation and biomass with 1x109 spores/ml being most effective. Cercospora piaropi formulated in corn oil lowered shoot length and biomass of water hyacinth more than M. roridum did.

Physiological Studies of Myrothecium Roridum: An Inciting Agent of Myrothecium Leaf Blight in Cotton

Background: Cotton is one of the most important cash crops in India. It is also called as “White gold” because of its agricultural as well as industrial importance. Myrothecium leaf blight is an emerging disease in cotton which is growing consistently throughout the country and has been reported to cause significant losses in major cotton growing tracts of odisha. Considering the importance of the disease, the present investigation has been taken up to study the physiology of the fungus. Methods: An experiment was conducted in-vitro during 2016-18 to investigate the effect of temperature and pH on the growth of M. roridum. Seven different nutrient media viz. Potato Dextrose Agar (PDA) medium, Potato Sucrose Agar (PSA) medium, Host Leaf Extract Agar (HEA) medium, Potato Carrot Agar (PCA) medium, Czapek’sdox Agar (ZA) medium, Richard’s Agar (RA) medium and Oat meal agar medium (OMA) were tested under in-vitro conditions to ascertain a suitable medium for the growth of M. roridum. Result: The investigation in laboratory conditions has revealed that out of seven nutrient media tested, maximum radial growth was recorded in Potato Sucrose Agar (PSA) with an average radial growth of diameter 76.06 mm and the least growth was recorded on Richard’s Agar with a diameter of 23.66 mm. The growth of the fungus was observed to be maximum at a temperature of 28oC with a diameter of 61.09 mm and the minimum average growth of 17.36 mm was recorded at 36oC. Studies on pH revealed that that the fungus grows well in neutral and slight alkaline medium (6.5 - 8.0).

Bioprospección modulada por la fenología, el sexo y el gradiente altitudinal: el caso de Baccharis conferta sobre Myrothecium roridum y Alternaria solani

Antecedentes: La bioprospección incluye la búsqueda de metabolitos secundarios para ser usados como fármacos, fungicidas o insecticidas. Los metabolitos secundarios en plantas pueden variar de acuerdo con su estado fenológico, sexo y por el ambiente, por lo tanto, estos elementos deben ser considerados en la bioprospección. Preguntas: 1) ¿Son diferentes las fenofases de Baccharis conferta entre organismos de diferente sexo y a lo largo de un gradiente altitudinal? y 2) ¿Tienen actividad biológica las diferentes concentraciones de extractos etanólicos de diferente sexo, fenofases y altitudes de B. conferta sobre el crecimiento in vitro de Myrothecium roridum y Alternaria solani? Especies estudiadas: Baccharis conferta Kunth, Myrothecium roridum Tode ex Fr. y Alternaria solani Sor. Sitio de estudio y fechas: Parque Nacional Cofre de Perote, septiembre 2017 a octubre 2018. Métodos: Registro mensual de fenofases en plantas de ambos sexos de B. conferta en tres altitudes del Cofre de Perote. Actividad antifúngica in vitro de extractos de B. conferta sobre Myrothecium roridum y Alternaria solani. Resultados: Observamos diferencias (p < 0.05) en la presencia y duración de las fenofases de B. conferta entre sexos y altitudes. También hubo diferencias significativas de los extractos provenientes de organismos de diferentes altitudes y fenofases sobre el crecimiento de M. roridum y A. solani. Conclusiones: Las fenofases de Baccharis conferta son diferentes entre sexos y a través de la altitud, además sus extractos (entre sexos y altitud) tienen efectos diferenciales sobre el crecimiento in vitro de Myrothecium roridum y Alternaria solani.