ICAR AIEEA PG Horticulture 14 July 2023 Shift-1 Paper

Hormonal regulation of flowering in mango (Mangifera indica):

• Ethephon (2-chloroethylphosphonic acid, an ethylene releasing compound) sprayed at $200\text{ ppm}$ along with urea promotes early flower bud differentiation and stimulates early flowering in off-year or irregular bearing mango varieties.
• Gibberellic acid ($GA_3$) strongly inhibits flowering in mango and promotes vegetative flushing.
• Indole-3-acetic acid (IAA) is an endogenous auxin not commercially used for floral induction in mango.
• Indole-3-butyric acid (IBA) is exclusively used for root initiation in cuttings and air layering.
  
  Option breakdown:
• Ethephon is widely recommended to trigger flowering and overcome biennial bearing.
• GA inhibits flowering in mango.
• IAA does not trigger early flowering.
• IBA is a rooting agent.

Classification of plant chimeras based on mutant cell distribution:

• Mericlinal chimera: The mutated tissue occupies only a portion (sector) of one cell layer (usually L-I or L-II) along the side of the shoot apex. It is unstable and often transitions into a periclinal chimera or reverts to wild type.
• Sectorial chimera: Mutated tissue spans across all layers (L-I, L-II, L-III) over a whole wedge-shaped sector of the apex.
• Periclinal chimera: An entire cell layer (or layers) surrounding the complete circumference of the apex consists of mutated cells; it is vegetative stable.
• Segmented chimera is not a standard cytological classification.
  
  Option breakdown:
• Mericlinal chimera perfectly fits one layer along the side of the apex.
• Spans all cell layers in a sector.
• Covers the entire layer completely.
• Non-standard term.

Biometrical techniques in plant breeding:

• Discriminant function analysis (pioneered by Fisher and applied by Smith to plant selection) combined with path coefficient analysis constructs selection indices to identify and discriminate elite genotypes from mixed populations based on multiple correlated traits.
• Diallel analysis evaluates general and specific combining ability of fixed sets of parents.
• Adaptability analysis assesses performance over varied environments.
• Stability analysis (e.g., Eberhart and Russell model) assesses genotype $\times$ environment interactions across locations.
  
  Option breakdown:
• Path and discriminant analysis is used to construct selection indices to discriminate elite lines.
• Measures combining abilities of crosses.
• Evaluates environmental adaptation.
• Evaluates GxE interaction stability.

Origin of ICAR-NRCB banana cultivar Udhayam:

• Bombay Green is a mango variety.
• Pidi Monthan is a culinary/cooking banana selection (ABB).
• Udhayam was released by ICAR-National Research Centre for Banana (NRCB), Tiruchirappalli, Tamil Nadu, as a superior high-yielding clonal selection from the popular cultivar Karpuravalli (Pisang Awak, ABB group). It produces large bunches with high sweet pulp and resistance to drought.
• High Gate is a dwarf mutant of Gros Michel (AAA).
  
  Option breakdown:
• Mango cultivar name.
• Monthan cooking banana.
• Clonal selection from Karpuravalli.
• Gros Michel semi-dwarf sport.

Morphological development in grapevines (Vitis vinifera):

• Calyptra (cap) is the fused petals that fall off during anthesis.
• Fork is an occasional branching pattern.
• Reflexed stamens occur in female flowers.
• In grapevines, inflorescences and tendrils are homologous structures occurring opposite the leaves. Inflorescences are borne on the basal nodes (typically nodes 3 to 6). Once flowering terminates, the nodes directly above develop tendrils instead of flower clusters.
  
  Option breakdown:
• Calyptra is a floral part.
• Non-morphological term.
• Flower sex trait.
• Tendrils develop opposite leaves at nodes immediately above the flowering zone.