| Inducing mutations type sphaerococcum in Triticum
aestivum ssp. vulgare with the aid of X-rays and ethyl, methan
sulphonate G. A. CHAVDAROV and K. P. DJELEPOV Dobrudja Agricultural Research Institute Gen. Toshevo, Bulgaria Seeds of the varieties Besostaya 1 and Mironovskaya 808 were treated in 1964 with ethyl methan sulphonate with concentrations of 0.1, 0.2, 0.4, and 0.6% using 10 ml solution for 100seeds at 25C during 24 hours. In the same year other samples of the two varieties were X-rayed in doses of 10, 15 and 20 kr and part of the seeds of M1 were treated with EMS concentrations of 0.2 and 0.4% applying the above-mentioned method. During 1966 from Besostaya 1 in M2 were selected 2, and in 1967 3, and from Mironovskaya 808 5 plants type sphaerococcum. In all from 93 plants 10 were mutations or in a ratio 9 : 1. They were characterized by a higher rate of general and productive tillering, were of lower height, short ears, more spikelets with lesser absolute weight of seeds and greater sterility compared with the starting forms. Two type mutations similar to T. sphaerococcum reported by SWAMINATHAN, JAGATHESAN and CHOPRA (8) were established from the varieties studied. The first type is characterized by short culms, stiff and erect flag leaves, with a spatulate ending, compact dense spikes, small, spherical grains and is perfectly similar to the corresponding subspecies of Triticum aestivum. We suppose this pertains to a mutation of the dominant gene Sp in a recessive direction which was localized by SEARS (6) as hemizygous-ineffective recessive in chromosome 3D (XVI). The second type differs from the first by longer and incompact spikes and shows considerable sterility. The 40 seeds received from this type of Besostaya 1 gave 36 plants of which 17 survived the winter. Of these, 13 plants were of the type sphaerococcum and 4 of the type vulgare which fully conforms with the ratio 3 : 1. This shows that this type is an inherited dominant and cannot be identified by the factor localized in 3D (XVI). The high percentage of failure to survive the sterility and the small number of analysed plants do not permit making a full and detailed genetic analysis. Maybe it is not a case of a fully dominant inheritance of this new gene but for a partial one as already reported by SWAMINATHAN, JAGATHESAN and CHOPRA (8), SCHMIDT, WEIBEL and JOHNSON (5) and SWAMINATHAN (7). A full interpretation of the character of inheritance and localization of the gene, which we will attempt to do with the help of monosomic series, should throw light on the second type of sphaerococcum effect. It is not impossible for the gene to be identical with the one of tetraploid wheats reported by SCHMIDT and JOHNSON (3, 4), BOZZINI (1), GUPTA and SWAMINATHAN (2). Receiving several types of sphaerococcum increases the possibilities of its practical use in breeding by induction of genes with lesser pleiotropic action. This will help solve the problem of transferring only sphaerical grain in T. aestivum ssp. vulgare without negative characters of T. sphaerococcum. The mutants obtained are of considerable interest for the evolution and taxonomy of the genus Triticum. Literature l) BOZZINI, A. 1965. Radiation Botany, Suppl. Vol. 5 : 525-535. 2) GUPTA, N. and M.S. SWAMINATHAN 1967. Current Science 36 : 19. 3) SCHMIDT, J.W. and V.A. JOHNSON 1963. Crop Science 3 : 98-99. 4) SCHMIDT, J.W. and V.A. JOHNSON 1966. WIS 22 : 5-6 5) SCHMIDT, J.W., D. WEIBEL and V.A. JOHNSON 1963. Crop Science 3 : 261-264. 6) SEARS, E.R. 1947. Genetics 32 : 102-103. 7) SWAMINATHAN, M.S. 1966. Hereditas, Suppl. Vol. 2 : 418-438. 8) SWAMINATHAN, M.S., D. JAGATHESAN and C.V. CHOPRA 1963. Current Science 32 : 539-540. (Received February 19, 1968) |