Gamma-rays Induced Reciprocal Translocation in Black Cumin (Nigella sativa L.)

Abstract

Gamma irradiations (5, 10, 20 kR) to Nigella sativa L. (black cumin) seeds (moisture content 7.5%) induced 5 translocation heterozygotes (P-14 and P-26 from 5 kR and P-32, P-36 and P-37 from 10 kR). P-14, P-32 and P-36 were viable translocations; while, P-26 and P-37 yielded only abortive seeds at R₁ following selfing and on open or controlled pollination. The translocation heterozygotes exhibited the formation of either a ring or a chain of 4 chromosomes in 38.71% to 77.72% meiocytes. Predominance of rings occurred in all translocation heterozygotes excepting P-26 where rings and chains were nearly equal. P-14 and P-26 had more adjacent orientation of quadrivalents than alternate; while, P-32, P-36 and P-37 demonstrated random orientations. The quadrivalent behaviour was found to be persistent in all generations of P-14, P-32 and P-36. The rings showed preponderance of adjacent orientation and the chains demonstrated frequent alternate orientation. Though normal 6/6 separation of chromosomes at AI was observed in 85.8, 83.3, 69.4, 82.3 and 86.4% cells of P-14, P-26, P-32, P-36 and P-37 respectively, pollen fertility was reduced in the heterozygotes (8.2 to 37.5%). F₁’s raised from intercrossing of P-14, P-32 and P-36 were meiotically assessed and the results indicated that same 2 non-homologous chromosomes were involved in translocation and the 2 longest chromosome pairs AA and BB (nucleolar pair) were suggested to be associated. P-14, P-32 and P-36 had marker phenotypic traits and characteristically P-36 possessed non-shattering capsule trait.