Abstract
A critical step in the production of doubled haploids is a conversion of the haploid embryos into plants. Our study aimed to recognize the reasons for the low germination rate of Avena sativa haploid embryos obtained by distant crossing with maize. Oat cultivars of ‘Krezus’ and ‘Akt’ were investigated regarding embryo anatomy, the endogenous phytohormone profiles, and antioxidant capacity. The zygotic embryos of oat were used as a reference. It was found that twenty-one days old haploid embryos were smaller and had a less advanced structure than zygotic ones. Morphology and anatomy modifications of haploid embryos were accompanied by extremely low levels of endogenous auxins. Higher levels of cytokinins, as well as tenfold higher cytokinin to auxin ratio in haploid than in zygotic embryos, may suggest an earlier stage of development of these former. Individual gibberellins reached higher values in ‘Akt’ haploid embryos than in the respective zygotic ones, while the differences in both types of ‘Krezus’ embryos were not noticed. Additionally to the hormonal regulation of haploid embryogenesis, the poor germination of oat haploid embryos can be a result of the overproduction of reactive oxygen species, and therefore higher levels of low molecular weight antioxidants and stress hormones.
Highlights
A critical step in the production of doubled haploids is a conversion of the haploid embryos into plants
The 21-day old zygotic embryos differed in their morphology from the haploid embryos (Fig. 1)
As we found no significant differences in the content of the investigated phytohormones in control oat zygotic embryos and zygotic embryos from the ovaries treated with 2,4-D, we can assume the exposure of the ovaries to 2,4-D does not significantly affect the endogenous hormonal profile of the embryos
Summary
A critical step in the production of doubled haploids is a conversion of the haploid embryos into plants. The advantages of using DH lines include acceleration of the breeding process by reducing the time to obtain homozygous lines as compared with inbreeding, and increased efficiency of selection in early generations. They can be successfully used as parents for F1 generation in hybrid seed production. Due to the low efficiency of the method, low weight of haploid embryos, and huge labor intensity the distant crossing requires, the content of endogenous phytohormones in haploid embryos has not been studied yet. They accumulate a few or a dozen days beyond pollination and fall during embryo maturation. Hormonal profiles of oat ovaries in which haploid embryos developed and ovaries in which no embryo developed were investigated, showing that the formation of a haploid embryo is accompanied by an increase in indole-3-acetic acid (IAA), trans-zeatin (t-Z), and kinetin (KN)[22]
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