Efficiency of induced mutagenesis at early stages (gametes, zygotes, proembryos) of ontogenesis in Nigella damascena L.
SummaryAn original technique has been developed of treating gametes, zygotes and early embryos of Nigella damascena L. with chemical and physical mutagens. A delay in fertilization and a decrease in the rate of cell division of the embryo and the endosperm after mutagen treatment have been found. Our method of treating gametes, zygotes and proembryos with chemical and physical mutagens is, by all criteria, superior to that of treating dry seeds. Treatment applied at early stages of ontogenesis not only induced a much higher mutation ratio compared with dry seeds, but also gave a broader mutation spectrum. The 55 types of hereditary change obtained affect the structure of vegetative and reproductive organs. Mutations which change the structure of the reproductive organs of flowers are of specific interest.The optimum dose for this object and the method of treatment which induces high mutation ratio (up to 96 % of families with changes) is 0.003p (16 hrs) for ethylenimine and 0.005p or 0.008p (16 hrs) for nitrosomethylurea. Treatment of dry seeds turned out to be much less effective.
Preliminary data on radiation-induced gamete sterility in M1 plants of Nicotiana tabacum
Abstract In order to study the sterility of male and female gametes of M1 plants arising from mutagenic treatments, 7 M1 plants of Nicotiana tabacum “purpurea” originating from irradiated zygotes (4 kR of γ-rays) were paired with 7 control plants. In each of the 7 pairs, self-pollinations of the control and M1 plants and both reciprocal crosses were performed 5 times. Data were obtained on pollen fertility (by a staining test), seed set, seed germination and number of seedlings per fruit. The female and the male gametes of an M1 plant were both found to produce sterility when crossed to a control plant. Comparison between the two reciprocal crosses showed that the average contribution of M1 egg cells to the total amount of sterility of the 7 M1 plants was no larger than that due to the corresponding pollen grains. The fact that the M1 pollen grains, despite their numerical superiority, determine a sterility effect no lower than that induced by the M1 egg cells, is explained by a greater ability of the female gametes to tolerate the genetic damage induced from the mutagenic treatment.
Inheritance in Nicotiana Tabacum Xxvii. Pollen Killer, an Alien Genetic Locus Inducing Abortion of Microspores Not Carrying It.
cytogenetic study of experimental introgression from N . plumbaginifolia (pbg) into N . tabacum (tbc) pursued laboratory several In the hybrid derivatives it was observed that genically controlled pollen abortion was associated with the addition of a pbg chromosome to the tbc complement. This chromosome also carried the locus (Bs) determining resistance or probably immunity to black shank, a serious disease of commercial tobacco caused by Phytophthora parasitica var. nicotianae. (For description see CLAYTON and AICAIVR-TRY 1950). Paradoxically, it developed that the pbg chromosome under study produced its effect on gametophytes in which it was not present. Thus, the male gametophytes containing a complete set of 24 tbc chromosomes degenerate while most of the functional pollen had the constitution 24 tbc + 1 pbg. This paper presents a description of the genetic aspects of the problem with some suggestions as to the possible method of action of the locus involved. Certain other phases of the larger investigation will be mentioned but only as they apply to the pollen lethal condition. The investigation was initiated by the late PROF. R. E. CLAUSEN who participated actively in the work presented here.