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.
Mutation induction by proembryo irradiation
Abstract In mutation breeding programs for many cereal crops, pollen irradiation has not proved to be a practical method for mutation induction, although theoretically the method of choice. The more commonly used procedure, that of irradiating dry seeds containing fully differentiated, “mature” embryos, has as its principal drawback the small size of the isomutant-carrying sector which can be produced in the R-1 plant. As a consequence of the small R-2 isomutant populations thus available for testing, screening procedures must usually be delayed until the R-3 or later generations. In this study, irradiation of proembryo stages has been investigated with regard to the practicality of using this method for mutation induction in cereal crops such as barley. By using albino mutations as genetic sector markers, we find that irradiation of barley proembryos with a relatively low total dose will yield much larger isomutant-carrying sectors and consequently far greater number of isomutant R-2 plants, with a comparable mutation frequency and less sterility than can be obtained by dry seed irradiation. Of great importance to the plant breeder is the possibility that the screening for less drastic mutations and multiple testing can be carried out at least one generation earlier by virtue of the larger isomutant populations produced by proembryo irradiation. Despite the more cumbersome handling involved during radiation treatment, the advantages which proembryo irradiation affords over dry seed irradiation would seem to recommend this method for cereal crops in those situations wherein pollen irradiation is not practical.
Ricerche Sugli Effetti Della Radiazione in Nicotiana. II: Modificazioni Morfologiche ed Irregolarità Meiotiche in Piante di Nicotiana Tabacum L. Derivate da Semi Trattati Con Neutroni Termici
RIASSUNTOSi riportano le osservazioni morfologiche e citogenetiche ricavate dall'esame di piante adulte nate da seme irradiato e quindi costituenti la prima generazione dopo radiazione neutronica [R(nth)1].L'analisi della varianza per i caratteri: altezza della pianta, numero di foglie per pianta, rapporto fra le dimensioni di una foglia mediana ha indicato che: a) le differenze fra l'altezza media delle piante test e delle piante I dose sono irrelevanti mentre le differenze tra piante I dose e piante II dose sono significative per tutte le cultivar; b) il numero delle foglie non varia in conseguenza del trattamento; c) il confronto dei rapporti fra le dimensioni fogliari e significativo soltanto tra piante I e II dose delle cv. Virginia bright e Xanthy-Yaka. In genere le piante I dose apparvero appena discoste dal normale mentre, tra quelle II dose, e specialmente nelle cv. Virginia bright e Xanthy-Yaka, erano numerose le piante con forti variazioni della morfologia e colore di foglie e fiori, epoca di f...