Practice question

In CGMS three-line scheme A-line designated as cytoplasmic male sterile female parent carrying sterile cytoplasm S derived from wild abortive source and non-restorer genotype rfrf in nuclear background, so phenotype fully male sterile with whitish anthers containing aborted pollen but female fertility normal. Because cytoplasm maternally inherited, progeny from any cross where A-line used as female inherits S cytoplasm and remains sterile unless restorer allele introduced from male parent. To multiply A-line, cross made with maintainer B-line sharing identical nuclear genome but normal fertile cytoplasm N, producing progeny retaining S cytoplasm from mother therefore sterile and genetically identical to A-line preserving trait. A-line thus serves as seed-bearing parent in commercial hybrid production field eliminating emasculation labor and ensuring hybrid purity through controlled pollen flow. This understanding supports competitive exam preparation for NEET, GATE and CSIR NET concepts linking genotype with phenotype through molecular pathways involving transcription factors, hormones and metabolic enzymes that regulate development, adaptation and reproductive biology in applied breeding programs.