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.

The C2H2 transcription factor SsZFH1 regulates the size, number and development of apothecia in Sclerotinia sclerotiorum

Sclerotinia sclerotiorum is a notorious phytopathogenic, Ascomycota fungus with a host range of over 600 plant species worldwide. This homothallic, Leotiomycetes species reproduces sexually through a multicellular apothecium which produces and releases ascospores. These ascospores serve as the primary inoculum source for disease initiation in the majority of S. sclerotiorum disease cycles. The regulation of apothecium development for this pathogen and other apothecium-producing fungi remains largely unknown. Here, we report that a C2H2 transcription factor SsZFH1 (zinc finger homologous protein) is necessary for the proper development and maturation of sclerotia and apothecia in S. sclerotiorum and is required for the normal growth rate of hyphae. Furthermore, ΔSszfh1 strains exhibit decreased reactive oxygen species (ROS) accumulation in hyphae, increased melanin deposition and enhanced tolerance to H2O2 in the process of vegetative growth and sclerotia formation. Infection assays on common bean leaves, with thin cuticles, and soybean and tomato leaves, with thick cuticles, suggest that the deletion of Sszfh1 slows the mycelial growth rate, which in turn affect the expansion of leaf lesions. Collectively, our results provide novel insights into the fungal factor mediating maturation of apothecia with additional effects on hyphae and sclerotia development.

تأثير بعض أنواع الفطريات على استنبات بذور الفول fababean صنف Minor في ليبيا

أُجريت التجربة خلال عامي 2019- 2020 في معمل أمراض النبات – كلية الزراعة – جامعة عمر المختار، بهدف دراسة تأثير البعض من أنواع الفطريات تضمنت Botrytis cinerea، Macrophomina phaseolina، Rhizoctonia solani، Sclerotinia sclerotiorum و Trichoderma harzianum على نسبة، وسرعة الإنبات، ومستوى تعفن الجذور في بذور الفول صنف Minor معملياً. تم تحضين البذور بعد تعقيمها سطحياً، وزراعتها في أطباق بتري على الوسط WA 1% الملقح بالفطريات المدروسة. سجلت التجربة اختلافات معنوية في نسبة الإنبات، و سرعته، ومستوى المرض. أفضل إنبات للبذور كان في معاملة T. harzianum (91.7%)، ولكن ليس أكثر من الشاهد (%100)، وأقل إنبات (25%) كان في البذور المعاملة بالفطرين M. phaseolina وR. Solani. كانت أعلى سرعة إنبات (3.1) للبذور في محيط Trichoderma أكثر من بذور الشاهد، والفطريات المُمْرِضة، في حين وصل مستوى المرض أعلاه (4.8) على الجُذير في معاملة الفطر R. solani، وسجل (0) في مُعاملتي الــــTrichoderma والشاهد. نستنتج من الدراسة أن معاملة البذور بالفطر T. harzianum يمكن أن تكون مفيدة لتحسين إنبات بذور الفول، بالإضافة إلى خفض الإنبات المتأخر.

Inhibition of the Growth and Development of Sclerotinia sclerotiorum (Lib.) De Bary by Combining Azoxystrobin, Penicillium chrysogenum VKM F-4876d, and Bacillus Strains

Sclerotinia sclerotiorum (Lib.) de Bary is a plant pathogen with a wide host range, which causes significant yield and storage losses of edible roots and other plant products. Due to its ability to sclerotia formation, the efficient control of this pathogen is complicated. The study of five Bacillus strains (B. subtilis VKM B-3154D, VKM B-3155D, VKM B-3505D, VKM B-2998D, and B. amyloliquefaciens VKM B-3153D) showed their ability to produce polyene antibiotics suppressing the growth and development of plant pathogenic fungi. The maximum concentration of polyene compounds was revealed for B. subtilis VKM B-2998D. A high in vitro antifungal activity of a dry mycelium biomass (DMP) of Penicillium chrysogenum VKM F-4876D, B. subtilis VKM B-2998D, and their combination has been demonstrated in relation to S. sclerotiorum. A combined application of DMP (0.3 g/L) and azoxystrobin at low dosage (2.5 mg/L) showed a high suppressing activity towards S. sclerotiorum (100% growth inhibition) including inhibition of a sclerotia formation that may be useful for the development of efficient methods of crop protection against this plant pathogen. A high performance liquid chromatography (HPLC) analysis of DMP revealed the presence of mevastatin suggesting the mechanism of the DMP antifungal activity is based on the blocking of the ergosterol (the main component of fungal cell walls) biosynthesis. The results of the study provide a prerequisite to the development of biopreparations to control S. sclerotiorum, whose use may provide a reduction of concentrations of fungicides used in agriculture and the corresponding reduction of their negative xenobiotic impact on the environment and recovery of the ecological balance in the soil.

CuZn and ZnO Nanoflowers as Nano-Fungicides against Botrytis cinerea and Sclerotinia sclerotiorum: Phytoprotection, Translocation, and Impact after Foliar Application

Inorganic nanoparticles (INPs) have dynamically emerged in plant protection. The uptake of INPs by plants mostly depends on the size, chemical composition, morphology, and the type of coating on their surface. Herein, hybrid ensembles of glycol-coated bimetallic CuZn and ZnO nanoparticles (NPs) have been solvothermally synthesized in the presence of DEG and PEG, physicochemically characterized, and tested as nano-fungicides. Particularly, nanoflowers (NFs) of CuZn@DEG and ZnO@PEG have been isolated with crystallite sizes 40 and 15 nm, respectively. Organic coating DEG and PEG (23% and 63%, respectively) was found to protect the NFs formation effectively. The CuZn@DEG and ZnO@PEG NFs revealed a growth inhibition of phytopathogenic fungi Botrytis cinerea and Sclerotinia sclerotiorum in a dose-dependent manner with CuZn@DEG NFs being more efficient against both fungi with EC50 values of 418 and 311 μg/mL respectively. Lettuce (Lactuca sativa) plants inoculated with S. sclerotiorum were treated with the NFs, and their antifungal effect was evaluated based on a disease index. Plants sprayed with ZnO@PEG NFs showed a relatively higher net photosynthetic (4.70 μmol CO2 m−2s−1) and quantum yield rate (0.72) than with CuZn@DEG NFs (3.00 μmol CO2 m−2s−1 and 0.68). Furthermore, the penetration of Alizarin Red S-labeled NFs in plants was investigated. The translocation from leaves to roots through the stem was evident, while ZnO@PEG NFs were mainly trapped on the leaves. In all cases, no phytotoxicity was observed in the lettuce plants after treatment with the NFs.

Multiple Species of Asteraceae Plants are Susceptible to Root Infection by the Necrotrophic Fungal Pathogen Sclerotinia sclerotiorum

The necrotrophic fungal pathogen Sclerotinia sclerotiorum can cause disease on numerous plant species, including many important crops. Most S. sclerotiorum-incited diseases of crop plants are initiated by airborne ascospores produced when fungal sclerotia germinate to form spore-bearing apothecia. However, basal stalk rot of sunflower occurs when S. sclerotiorum sclerotia germinate to form mycelia within the soil which subsequently invade sunflower roots. To determine if other plant species in the Asteraceae family are susceptible to root infection by S. sclerotiorum, cultivated sunflower (Helianthus annuus L.) and seven other Asteraceae species were evaluated for S. sclerotiorum root infection by inoculation with either sclerotia or mycelial inoculum. Additionally, root susceptibility of sunflower was compared to that of dry edible bean and canola, two plant species susceptible to S. sclerotiorum but not known to display root-initiated infections. Results indicated that multiple Asteraceae family plants are susceptible to S. sclerotiorum root infection after inoculation with either sclerotia or mycelium. These observations expand the range of plant hosts susceptible to S. sclerotiorum root infection, elucidate differences in root inoculation methodology, and emphasize the importance of soil-borne infection to Asteraceae crop and weed species.