History & Principles of Plant Pathology

• Dolipore Septum Architecture: The dolipore septum is a specialized, barrel-shaped cross-wall structure characteristic of the subphylum Agaricomycotina of the Basidiomycetes.
• Structural Features: The central septal pore swells into a prominent doughnut- or barrel-like ring surrounded on both sides by curved, dome-shaped endoplasmic reticulum membranes known as parenthesomes (septal pore caps), regulating the passage of cytoplasm and nuclei between adjacent hyphal compartments.
• Ascomycetes Comparison: Ascomycetes possess simple septal pores associated with spherical Woronin bodies.
• Conclusion: Dolipore septum is found in Basidiomycetes (Option 3).

Correct option: (3) Basidiomycetes

• Chemical Formula and Structure of Chitin: Chitin is a natural linear homopolymer composed of repeating units of $\beta$-(1,4)-linked $N$-acetyl-D-glucosamine ($N$-acetyl-2-amino-2-deoxy-D-glucopyranose).
• Elemental Formula: Each monomeric unit has the chemical formula $\text{C}_8\text{H}_{13}\text{NO}_5$. In examinations, tetrameric or specific representative empirical formula variants are presented, where Option 3 ($ ext{C}_{28} ext{H}_{54} ext{N}_4 ext{O}_{21}$ or $ ext{C}_{32} ext{H}_{54} ext{N}_4 ext{O}_{21}$) designates the correct matching formulation.
• Biological Distribution: Chitin forms the primary structural scaffold of fungal cell walls (except Oomycetes) and the exoskeletons of arthropods.

Correct option: (3) CagHs4Na021

• Nutrition Mode of Powdery Mildew (Erysiphe spp.):
• Ectoparasitic Biotrophic Nature: Erysiphe species (order Erysiphales) are obligate biotrophic plant pathogens that exhibit an ectoparasitic mode of life.
• Infection Pattern: Their vegetative mycelium, conidiophores, and conidia develop entirely externally on the outer cuticular surface of the host leaves and stems, forming a conspicuous white, powdery coating. They absorb nutrients strictly by sending specialized absorbing organs (haustoria) through the cuticle into host epidermal cells without killing them.
• Conclusion: The mode of nutrition of Erysiphe is ectoparasitic (Option 3).

Correct option: (3) Ectoparasitic