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1

Microsporogenesis in two alloplasmic isonuclear strains of tobacco Nicotiana tabacum L. cv.Zamojska 4 with the cytoplasms of N.knightiana Goodspeed and N.raimondi Macbride

100%
Berbec A.
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2

Abnormal meiosis in tetraploid genotypes of Brachiaria brizantha (Poaceae) induced by colchicine: its implications for breeding

86%
Mendes-Bonato A. B., Ferrari F. M., Souza K. A. M., Pessim C., Calisto V., Pagliarini M. S., Valle_do C. B.
Journal of Applied Genetics
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2009
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vol. 50
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issue 2
83-87
EN
Meiotic behavior was analyzed in 6 progenies from 3 artificially induced tetraploid (2n = 4x = 36) sexual genotypes (C31, C41, and C48) of the normally apomictic Brachiaria brizantha (Hochst. ex A. Rich.) Stapf., syn. Urochloa brizantha (Hochst. ex A. Rich.) R. Webster. These are key plants to allow intraspecific hybridization of this important forage species, widely used for pastures in the tropics. The percentage of abnormal cells among the plants ranged from 39.8% to 63.2%. In the single plant derived from C48, only the common meiotic abnormalities typical of polyploids were observed, while in plants derived from C31 and C41, a distinct behavior was found. In the majority of cells of those plants, the chromosomes remained scattered in the cytoplasm in the first division, without forming a metaphase plate. This abnormality blocked chromosome movements at anaphase I. Several micronuclei of various sizes were formed and, after the occurrence of an irregular first cytokinesis, the meiocytes progressed normally to the second division, generating polyads with unbalanced microspores. Pollen viability was not correlated with meiotic abnormalities. The importance of these findings to the Brachiaria breeding program is discussed. The sexual progeny of C48 seems most suitable as female parents to be used in intra- and interspecific hybridization.
3

Obtaining homozygous carrot plants with the aid of androgenesis in anther cultures

86%
Gorecka K., Krzyzanowska D., Kiszczak W., Kowalska U., Gorecki R.
Biotechnologia
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2008
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issue 2
142-152
EN
Experiments with anther cultures of 22 carrot cultivars were carried out to study the effect of various factors on the effectiveness of embryogenesis in these cultures. The factors included: the stage of microsporogenesis, genotype, training of donor plants and their growth conditions. A modified B5 medium (Gamborg, et al. 1968) containing 500 mg L-1 glutamine, 100 mg L-1 serine, 0.1 mg L-1 of 2,4D, 0.1 mg L-1 NAA, 100 g L-1 sucrose and 6.5 g L-1 agar were used to induce androgenesis. Regeneration was carried out on MS media and B5 with reduced concentration of sucrose at 20 g L-1 without aminoacids and hormones or with small amount of hormones. Substrates that were a mixture of various components, such as peat, sand, mineral wool and charcoal, were used for adaptation. Ploidy of the obtained plants was determined by cytometry method. Homozygosity of the plants was established using two isoenzymatic systems: PGI ? phosphoglucose isomerase, and AAT ? aspartate aminotransferase. Anatomical studies of embryogenesis during anther cultures were also carried out to confirm the androgenetic origin of embryos. It was found that the uninucleate stage was the most suitable time to stimulate microspores to produce embryos, and that bud length was a good external indicator of the stage of microsporogenesis. The studied cultivars differed in their ability to undergo androgenesis in vitro. It was shown that it was not necessary to remove all shoots and umbels except the main one. Generally, the embryos were obtained regardless of the way the donor plants were trained, even when the plants were not trained at all. The donor plants grown in a greenhouse produced more embryos than the plants grown in the field. On MS and B5 media without hormones, used to regenerate plants from embryos, secondary embryogenesis was found to take place followed by a conversion of embryos to complete plants, which subsequently resulted in better adaptation (more than 80% of plants became adapted). Cytometric studies revealed that more than 90% of the obtained androgenetic plants had a doubled chromosome complement. By analyzing the AAT and PGI isoenzymes, it was found that the obtained carrot androgenetic plants were homozygotes. Anatomical studies confirmed that embryos were formed from microspores.
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