[The level of genetic variability of cells in prolonged suspension culture of Arabidopsis thaliana].

The level of heterogeneity and genetic variability of cells in a suspension of Arabidopsis thaliana cultured in vitro for more than seven years was studied. The considerable heterogeneity of the suspension in cell size was shown. As revealed by nuclear DNA cytophotometry, the suspension culture was mixoploid and the amount of DNA in the cells varied from 4 to 16 C. However, PCR with 6 RAPD- and 4 ISSR-primers and their intra-group combinations showed the lowest degree of variability of DNA markers. The genetic distances of clones obtained from a suspension culture of the parent plant were only 1.5%. Differences between the clones were identified with only one pair of 31 primer combinations tested, indicating low level of genetic heterogeneity of the suspension. The results showed that variations in the amount of DNA in the suspension culture cells are not accompanied by significant changes in the DNA sequence.

[Freezing of dehydrated calluses of spring wheat (Triticum aestivum L.) in liquid nitrogen and their morphogenetic potential].

A cryopreservation method developed earlier was modified for freezing the calluses derived from mature embryos of four spring wheat (Triticum aestivum L.) pure lines. The effects of individual stages of cryopreservation protocol on the water content, number of calluses resuming growth, and rate of morphogenesis were analyzed. Growth resumption was observed in 90.5-100% of the calluses after dehydration and in 93.3-100% after freezing-thawing. The number of calluses displaying signs of morphogenesis considerably decreased after dehydration but remained almost the same after freezing-thawing.

[Analysis of specific RAPD- and ISSR-fragments in somaclonal maize (Zea mays L.) and development of SCAR markers based on them]. / Vyiavlenie spetsificheskikh RAPD- i ISSR-fragmentov u somaklonov kukuruzy (Zea mays L.) i sozdanie na ikh osnove SCAR-markerov.

RAPD (Random Amplified Polymorphic DNA) and ISSR (Inter Simple Sequence Repeats) markers were used to analyse the genetic divergence between the regenerated plants derived from callus cultures and the original maize line A188. Analysis of polymorphism by using 38 RAPD- and 10 ISSR-oligonucleotide primers showed that the differences between eight examined somaclones and the original line ranged from 6.5 to 23%. As confirmed using new primers, the regenerants derived from callus cultures grouped into two clusters according to their origin. The regenerants isolated from calluses grown for eight months differed from one another and the original line to a larger extent than the regenerants obtained from two-month callus cultures. In some somaclones, molecular marking of the regenerants revealed specific RAPD and ISSR fragments that were absent in other somaclones or the original maize line. On the basis of six specific fragments (five RAPD and one ISSR), SCAR (Sequence Characterized Amplified Region) markers were developed. Specific polymorphism revealed with random primers was completely confirmed using five SCAR markers. Polymorphism of one SCAR marker differed from that revealed with random primers. Five SCAR fragments were inherited as simple dominant traits. One SCAR fragment displayed codominant inheritance.

[RAPD-analysis of corn somaclones]. / RAPD-analiz somaklonov kukuruzy.

The genetic difference between maize line A188 and A188-derived somaclones was assessed via analysis of randomly amplified polymorphic DNA (RAPD). In total, 15 out of 17 decanucleotide primers used each allowed amplification of 2-17 fragments ranging 200-2000 bp. The RAPD patterns did not differ between individual plants of line A188, which demonstrated again its high genetic homogeneity. The difference between the initial line and the somaclones was high, ranging 64-74%. On evidence of the genetic divergence, the somaclones formed two clusters. The distribution of somaclones between these clusters was consistent with their origin.