Evolution in vitro du contenu en ADN nucléaire et de la ploïdie des embryons polliniques du Datura innoxia

Abstract

Nuclear DNA content was estimated by densitometry in three stages of in vitro development of Datura innoxia Mill. embryos (3–25 cells) obtained from pollen. At the same time, the sizes, structure and arrangements of nuclei in young embryos were examined and chromosome numbers of adult embryos were determined. Results showed that: (i) Embryos originating from pollen were haploid, diploid, aneuploid, or myxoploid. Proportions of each ploidy level varied with cell numbers in embryos, and with ages of cultures, (ii) Young diploid embryos were very regular and had dense nuclei of one type only. Haploid embryos were less regular; they had one or two types of nuclei whose texture was often looser than that of diploid embryo nuclei. Aneuploid and myxoploid embryos had very irregular structures, (iii) Initiation of androgenetic embryos was spread out in time from the 2nd to the 12th day of culture. Embryos showed different nuclear features if they were initiated at the beginning, in the middle, or at the end of the culture period. Embryos initiated early were mostly haploid and the proportion of abnormal ploidy embryos was low during the 1st week of culture. In Datura innoxia, therefore, embryos must be taken after 1 week of culture to obtain the population which is most favourable to further genetic breeding. [Journal translation]