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Morphological observations of Diplodia maydis on synthetic and natural substrates as revealed by scanning electron
Abstract:
Mycelial and spore morphology of Diplodia maydis were investigated by using scanning electron microscopy after growth on various media and natural substrates (oat and corn kernels, and corn husks). Of several specimen preparation methods studied, Parducz fixation followed by critical-point or freeze-drying gave adequate preservation for pycnidia, mycelia, and spores. Morphological characteristics were similar in rotary and reciprocal shaker cultures and differed from that found in stationary cultures in the amount of slime-like material produced and precipitated matter on the mycelial surfaces. In general, mycelial surfaces were smooth. Large areas of coalesced material were present in all samples examined. Slime-like material produced in liquid media appeared as a finely laced net, randomly appearing throughout the mycelia with bead-like structures present along the net. A fine netting also was observed interspersed among the spores inside the pycnidia obtained from oats. Slime-like material was observed to cover the pycnidia produced on oat and corn kernels. In the latter case, the spores were less protected by the outer slime-like covering. Thickened node-like structures were observed in mycelial mats produced in modified Fries 2 medium, on potato dextrose agar plates, and on infected oats. Round and ovate thickened node-like structures were observed in mycelium produced on corn kernels. In general, node-like structures were less abundant in mycelia from naturally infected substrates. Conidia were commonly rounded to tapered and two celled, with a distinctive ridged septum at the middle. Dried spores were collapsed in a characteristic flask-like fashion.
Insights
Scanning electron microscopy revealed Diplodia maydis morphology. Specimen preparation and growth conditions significantly influenced the appearance of mycelia, spores, and pycnidia, impacting disease research.
Area of Science:
- Mycology
- Plant Pathology
- Microscopy
Background:
- Diplodia maydis is a significant plant pathogen.
- Understanding its morphology is crucial for disease management.
- Previous studies have not fully detailed its ultrastructure under various conditions.
Purpose of the Study:
- To investigate the mycelial and spore morphology of Diplodia maydis.
- To evaluate the effects of different growth media and specimen preparation techniques.
- To provide detailed ultrastructural insights for pathogen identification and control.
Main Methods:
- Scanning electron microscopy (SEM) was employed.
- Specimens were grown on various media and natural substrates (oat kernels, corn kernels, corn husks).
- Parducz fixation followed by critical-point or freeze-drying was optimized for specimen preservation.
Main Results:
- Mycelial surfaces were generally smooth, with coalesced material present.
- Slime-like material formed a net-like structure in liquid media and covered pycnidia on kernels.
- Node-like structures were observed on mycelia, varying in abundance based on substrate.
- Conidia were typically two-celled with a ridged septum, collapsing into a flask-like shape when dried.
Conclusions:
- SEM is effective for visualizing Diplodia maydis morphology.
- Growth conditions and preparation methods significantly alter observed ultrastructural features.
- Detailed morphological data can aid in differentiating Diplodia maydis and understanding its pathogenesis.