IDENTIFICACIÓN DE MICROORGANISMOS PATÓGENOS EN EL CULTIVO DE (Stevia Rebaudiana Bertoni)

En campos comerciales de Stevia rebaudiana localizados en los centro poblados Las Palmas y Esperanza la se determinó la incidencia y severidad de enfermedades ocasionales por microorganismos patógenos. La investigación se desarrolló en fases de reconocimiento de la sintomatología, identificación de agentes causales y determinación de pruebas de patogenicidad. Se encontraron 8 hongos, como agentes causales de los marchitamientos, necrosis de la raíz, manchas foliares y necróticas. 8 hongos, Fusarium sp., Rhizoctonia sp., Sclerotinia sclerotiorum, Sclerotium rolfsii. Cuyos daños ocasionan en los tallos y raíces, Septoria sp., Cercospora sp., Alternaria sp., Oidium. La Esperanza se ha encontrado más plantas infestadas por una mayor diversidad de microorganismos. Los microorganismos no mostraron preferencias entre hojas y tallos y raíz. Para ambas zonas los microorganismos con mayor presencia fueron. Fusarium, Septoria y Sclerotinia sclerotiorum, Sclerotium rolfsii.

Fungal Species Causing Maize Leaf Blight in Different Agro-Ecologies in India

Foliar diseases of maize cause severe economic losses in India and around the world. The increasing severity of maize leaf blight (MLB) over the past ten years necessitates rigorous identification and characterization of MLB-causing pathogens from different maize production zones to ensure the success of resistance breeding programs and the selection of appropriate disease management strategies. Although Bipolaris maydis is the primary pathogen causing MLB in India, other related genera such as Curvularia, Drechslera, and Exserohilum, and a taxonomically distant genus, Alternaria, are known to infect maize in other countries. To investigate the diversity of pathogens associated with MLB in India, 350 symptomatic leaf samples were collected between 2016 and 2018, from 20 MLB hotspots in nine states representing six ecological zones where maize is grown in India. Twenty representative fungal isolates causing MLB symptoms were characterized based on cultural, pathogenic, and molecular variability. Internal Transcribed Spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GADPH) gene sequence-based phylogenies showed that the majority of isolates (13/20) were Bipolaris maydis. There were also two Curvularia papendorfii isolates, and one isolate each of Bipolaris zeicola, Curvularia siddiquii, Curvularia sporobolicola, an unknown Curvularia sp. isolate phylogenetically close to C. graminicola, and an Alternaria sp. isolate. The B. zeicola, the aforesaid four Curvularia species, and the Alternaria sp. are the first reports of these fungi causing MLB in India. Pathogenicity tests on maize plants showed that isolates identified as Curvularia spp. and Alternaria sp. generally caused more severe MLB symptoms than those identified as Bipolaris spp. The diversity of fungi causing MLB, types of lesions, and variation in disease severity by different isolates described in this study provide baseline information for further investigations on MLB disease distribution, diagnosis, and management in India.

Alternaria leaf spot of broccoli caused by Alternaria alternata in Bangladesh

This study aimed to isolate and characterise the pathogen associated with Alternaria leaf spot on broccoli and to evaluate the inhibitory effects of fungicides against it. We isolated and identified the fungal pathogen as Alternaria sp. using morphological and cultural methods. Based on the aligned sequences of the internal transcribed spacer (ITS) and molecular phylogenetic analysis by the neighbour-joining method, the isolates (Ab1 and Ab2) were confirmed as Alternaria alternata. The conidia of the isolates were dark brown, cylindrical, obclavate to muriform. The conidiophores were olivaceous brown, septate, and branched. The conidial morphology of the isolates ranged from 52.4–92.4 × 10–20 μm with 2–6 transverse and 0–3 longitudinal septa. Both isolates yielded positive results in the pathogenicity test on broccoli leaves by developing brown and circular spots with concentric rings on the leaves surrounded by yellow halos. The culture studies revealed that the maximum growth of the pathogen was obtained at 30 °C and pH 6.0. Tilt 250 WC showed the highest potential in suppressing the mycelial growth of the A. alternata in vitro at a concentration as low as 50 µg/mL. The results from this study contributed to the positive identification of the pathogen and characterised A. alternata as a destructive pathogen of broccoli which may be successfully controlled by the fungicide Tilt.

A marine fungus efficiently degrades polyethylene

Plastics pollution has been a global concern. Huge quantities of polyethylene (PE), the most abundant and refractory plastic in the world, have been accumulating in the environment causing serious ecological problems. However, the paucity of microorganisms and enzymes that efficiently degrading PE seriously impedes the development of bio-products to eliminate this environmental pollution. Here, by screening hundreds of plastic waste-associated samples, we isolated a fungus (named Alternaria sp. FB1) that possessing a prominent capability of colonizing, degrading and utilizing PE. Strikingly, the molecular weight of PE film decreased 95% after the fungal treatment. Using GC-MS, we further clarified that a four-carbon product (named Diglycolamine) accounted for 93.28% of all degradation products after the treatment by strain FB1. We defined potential enzymes that involved in the degradation of PE through a transcriptomic method. The degradation capabilities of two representative enzymes including a laccase and a peroxidase were verified. Lastly, a complete biodegradation process of PE is proposed. Our study provides a compelling candidate for further investigation of degradation mechanisms and development of biodegradation products of PE.

State and prospects of modern research in biotechnology of licens as a medicinal raw material

Based on the content analysis of the sources of patent and scientific literature on the biotechnology of lichens as a medicinal raw material, systematized modern information is provided, as well as original experimental data regarding the cultivation of botanical species of lichens of various ecological and geographical groups under controlled conditions. Since ancient times, lichens havebeen used as medicines and are included in the pharmacopoeias of various countries. At present, methodological approaches have been developed for the cultivation of lichens (genera Usnea, Rhinocarpon, Umbilicara ) and their components: phycobiont (genera Nostoc, Chlorella ), mycobiont ( Petrusaria pertiza, Leydea parasema, Alternaria sp.). The main biologically active compounds (usnic acid, lichenin, cetrarin, water-soluble vitamins, calcium oxalate) and the pharmacological effects caused by them (antimicrobial, stimulating appetite, enveloping, anti-inflammatory, anti-burn, regenerating). Biotechnological approaches can be implemented for species cloning, reproduction, creation of a bank of cell cultures of lichens and their components in order to preserve economically valuable producers in an active state and develop technologies for obtaining biomass and pharmacologically valuable biologically active compounds.

Fungal Pathogens Associated with Damping-off Disease of Cashew Seedlings in Nigeria

Aim: This study was designed to isolate fungal pathogens associated with damping-off of cashew seedlings. Study Design: The cashew seedlings for this study were selected randomly from a number of infected cashew seedlings in the screen house. Methodology: Associated fungal pathogens were grown on potato dextrose agar (PDA) and identified using their characteristics and morphological features observed under the microscope with reference to published identification manuals. Results: The result showed that damping-off of cashew seedling is mostly associated with fungal pathogens such as such as Fusarium spp, Colletotrichum gloeosporioides, Pythium spp., Alternaria sp., Curvularia sp., Aspergillus niger, and Lasiodiplodia theobromae. However, Fusarium spp, and Pythium spp. were predominant and frequently isolated than other pathogens. Conclusion: The knowledge of these pathogens is important for designing strategies to safeguard cashew plant health against diseases in order to ensure sustainable cashew production in Nigeria.