Cytogenetic Characterization of Induced Sterility in Ornithogalum virens L.

Cytogenetic investigation was carried out in 2 gamma-ray induced semisterile plants for 2 consecutive years in Ornithogalum virens L. They were characterized as translocation heterozygotes I and II (TH-I and TH-II). Meiotic analysis revealed regular presence of a quadrivalent in the microsporocytes of both the plants at diakinesis and metaphase I. Close association of the quadrivalent with nucleolus was the unique feature in TH-I. This might happen through reciprocal translocation between 2 non-homologous pairs of chromosomes, 1 pair possessing secondary constrictions. Non-adherence of the quadrivalent with nucleolus, on the other hand, rules out involvement of the satellited chromosomes in reciprocal translocation and quadrivalent association in TH-II. Chain shaped quadrivalent was more common in TH-I than ring configuration, while the reverse was true for TH-II, possibly due to variation in the size of the interchanged segments. Longer segments offering better scope of chiasma formation may facilitate origin of a ring of four; but a chain quadrivalent may arise due to shorter size of interchanged segments providing little or no chance of chiasma. Quadrivalent association may be primarily attributed for pollen sterility which enhanced possibly due to high incidence of ring configuration and adjacent orientation in TH-II. Conversely, frequent occurrence of chain quadrivalent and alternate orientation might have restored fertility appreciably in TH-I. Anaphasic anomalies were identical in both.