| Karyotype of Triticum zhukovskyi Men. et Er. M. UPADHYA and M.S. SWAMINATHAN Division of Botany, Indian Agricultural Research Institute, New Delhi, India V.L. Menable and A. Eritzan described in 1957 a new hexaploid species (2n=42) named T. zhukovskyi. This species occurs in Western Georgia in the same habitat as the tetraploid T. timopheevi. According to Jakubziner (Proc. 1st International Wheat Genetics Symposium, 1958, pages 207-220), T. zhukovshyi resembles T. timopheevi in ear morphology and growth characteristics and may have been derived from it. During a comparative study of the karyotypes of all hexaploid Triticum species, we found that T. zhukovskyi has a pair of satellited chromosomes possessing a supernumerary constriction of the type found in T. macha Dek. et Men. by Bhaduri and Ghosh (Cytologia 20, 148 -149, 1955). The secondary constriction and supernumerary constriction are separated from each other by a minute chromosome segment. The pair of Sat-chromosomes with supernumerary constriction present in T. zhukovskyi resembled one such pair in T. macha with regard to relative length and index value (short arm/long arm). While two such pairs occur in T. macha only one pair was found in T. zhukovskyi. T. macha also occurs in Western Georgia and Jakubziner believes that it might have arisen from the tetraploid species, T. paleocolchicum Men. The type of Sat-chromosomes with supernumerary constrictions found in T. macha and T. zhukovskyi has not so far been found in any other hexaploid Triticum species. We hence feel that these two species may be derived from a common stock. |