Laboratory & Analytical Techniques

• The Taxonomic Rank 'Pathovar': In botanical and phytopathological nomenclature, the term pathovar (pv.) is defined by the International Code of Nomenclature of Bacteria (ICNB) specifically for plant pathogenic bacteria.
• Definition: A pathovar is an infrasubspecific taxon denoting a bacterial strain or set of strains with the same or similar characteristics, differentiated based on distinctive pathogenicity or host range on specific plant species or cultivars (e.g., Xanthomonas campestris pv. campestris, Pseudomonas syringae pv. phaseolicola).
• Other Groups: For fungi, similar intraspecific variants are termed forma specialis (f. sp.) or races; for nematodes, races or biotypes are used.
• Conclusion: Pathovar is used in bacterial taxonomy (Option 4).

Correct option: (4) Bacteria

• Taxonomy and Characteristics of Dickeya chrysanthemi:
• is true: Originally described and formerly known as Erwinia chrysanthemi (or Pectobacterium chrysanthemi) before reclassification into the new genus Dickeya.
• is true: It is a Gram-negative, facultatively anaerobic, non-spore-forming bacillus belonging to the family Pectobacteriaceae.
• is false: It possesses peritrichous flagella (typical of Enterobacterales), not polar flagella.
• is false: It produces pectolytic enzymes causing soft rot and slow-wilt, but does not produce fluorescent pigments (fluorescent pigments are diagnostic of Pseudomonas).
• Conclusion: Statements (A) and (D) only are true (Option 4).

Correct option: (4) (A) and (D) only.

• Banana Diseases and Management Strategies:
• Pair-by-Pair Matching:
• Panama disease (Fusarium oxysporum f. sp. cubense) $\rightarrow$ (III) Flood fallowing: Soil-borne chlamydospores survive for decades; flooding the infested field with water for 6–12 weeks creates anaerobic soil conditions that eradicate the fungus.
• Sigatoka disease (Pseudocercospora musae/fijiensis) $\rightarrow$ (I) Fungicidal spray: Airborne foliar ascospores/conidia cause extensive leaf spot; managed with systemic fungicidal sprays (triazoles, strobilurins) mixed with mineral oil.
• Moko disease (Ralstonia solanacearum) $\rightarrow$ (IV) Clean planting material: Vascular bacterial wilt managed via strict sanitation, eradication of infected mats, and disease-free tissue-cultured plantlets.
• Bunchy top of Banana (BBTV) $\rightarrow$ (II) Domestic Quarantine: Transmitted by banana aphid (Pentalonia nigronervosa); strict domestic quarantine prohibits transport of vegetative suckers from infected zones (Assam, Kerala) to uninfected states.
• Correct Choice: Option 2 represents (A)-(III), (B)-(I), (C)-(IV), (D)-(II).

Correct option: (2) (A) - (III), (B) - (1), (C) - (IV), (D) - (HI)

• Integrated Cultural and Chemical Disease Management:
• Pair-by-Pair Matching:
• Avoid wounding $\rightarrow$ (II) Fusarium spp.: Vascular wilt fungi (Fusarium oxysporum) penetrate roots through natural cracks or mechanical wounds made by cultivation tools and nematodes; avoiding root injury prevents infection.
• Certified seeds $\rightarrow$ (III) Viruses: Production and distribution of certified virus-free seed tubers/seeds is the most critical measure to manage seed-borne viruses.
• Good drainage $\rightarrow$ (I) Pythium spp.: Damping-off caused by Pythium zoospores requires free soil water; raised nursery beds and excellent drainage prevent spore motility and disease development.
• Spraying chemicals before harvesting $\rightarrow$ (IV) Phytophthora spp.: Late blight sprays on foliage before harvest kill sporangia, preventing tuber rot during lifting and storage.
• Correct Choice: Option 4 matches (A)-(II), (B)-(III), (C)-(I), (D)-(IV).

Correct option: (4) (A) - (II), (B) - (III), (C) - (1), (D) - (IV)