Genetics & Plant Breeding - ICAR JRF/SRF 2024

• Assertion (A) is True: Genetic Male Sterility (GMS) lines cannot produce viable pollen and therefore cannot self-pollinate. To maintain the GMS line (female parent), it must be continually maintained by backcrossing with an identical heterozygous male-fertile maintainer line ($Ms/ms$), which yields a 1:1 segregating progeny of fertile ($Ms/ms$) and sterile ($ms/ms$) plants.
• Reason (R) is True: The male sterility phenotype in monogenic GMS is governed by a recessive nuclear gene ($ms$). Because the homozygous recessive genotype ($ms/ms$) is completely sterile and the maintainer parent provides the dominant allele ($Ms$), heterozygous crossing maintains the recessive allele in the population.
• Relationship: Because the recessive nuclear gene ($ms$) governs the phenotype, cross-pollination with heterozygous plants ($Ms/ms$) is biologically mandatory to generate sterile segregants in every maintenance generation. Thus, Reason (R) correctly explains Assertion (A).
• Conclusion: Both (A) and (R) are true and (R) is the correct explanation of (A) (Option 1).

Correct option: (1) Both (A) and (R) are true and (R) is the correct explanation of (A)

• Working Principles of Seed Cleaning and Separation Machinery:
• Specific Gravity Separator: Separates seed admixtures based on differences in specific density and terminal velocity in an air stream $\rightarrow$ effectively removes (I) Partially filled achenes / light, shriveled seeds.
• Indented Cylinder Separator: Employs centrifugal force and hemispherical pockets on a rotating drum to lift and separate particles based on length differences $\rightarrow$ removes (II) Broken caryopsis / short weed seeds.
• Dodder Mill (Velvet Roll Mill): Separates seeds utilizing contrasting surface roughness and texture differences via counter-rotating flannel/velvet cloth-covered rollers $\rightarrow$ removes (III) Rough surfaced admixture.
• Spiral Separator: Operates purely on gravitational acceleration and degree of roundness/centrifugal displacement $\rightarrow$ efficiently separates spherical seeds from flat or angular particles, isolating (IV) Splits in soybean.
• Systematic Match: (A)-(I), (B)-(II), (C)-(III), (D)-(IV) corresponds to Option 4.

Correct option: (4) (A) - (1), (B)~ (I), (C) - (ill), (D)- (V)