B-line in CGMS is used to:
B-line or maintainer line defined as fertile counterpart isogenic to A-line for nuclear genes but carrying normal fertile cytoplasm N and homozygous non-restorer alleles rfrf. Function maintains male sterile A-line because when A-line cytoplasm S mother crossed with pollen from B-line, offspring inherits S cytoplasm from maternal parent causing male sterility while nuclear genome remains rfrf identical to both parents. B-line itself self-fertile due to N cytoplasm compensating, producing sufficient seeds for propagation. Without B-line, A-line cannot be multiplied sexually because selfing yiel
Ref: Singh BD Maintainer line role; Acquaah Principles B-line multiplication; ICAR Hybrid seed Handbook.
