Assessment of intergenomic recombination through GISH analysis of F1, BC1 and BC2 progenies of Tulipa gesneriana and T. fosteriana

Abstract

Using 23 F1 hybrids, 14 BC1 and 32 BC2 progenies, the genome composition of Darwin hybrid tulips was analysed through genomic in situ hybridisation (GISH) of somatic chromosomes. All plants were diploids (2n = 2x = 24) with the exception of one tetraploid BC1 (2n = 4x = 48) and one aneuploid BC2 (2n = 2x ? 1 = 25) hybrid. Morphometric analysis in F1 hybrids revealed a difference in the total length of chromosomes representing genomes of T. gesneriana and T. fosteriana, where the percentage of each genome equaled 55.18 ± 0.8 and 44.92 ± 0.6% respectively. GISH distinguished chromosomes from both parent genomes although there was a lack of consistent chromosome labelling in some cases. In both T. gesneriana and T. fosteriana chromosomes some segments of heterochromatin in the telomeric and intercalary regions exhibited a higher intensity of fluorescence. In situ hybridisation with 5S rDNA and 45S rDNA probes to metaphase chromosomes of F1 hybrids showed that these regions are rich in rDNA. A notable feature was that, despite genome differences, there was a considerable amount of intergenomic recombination between the parental chromosomes of the two species as estimated in both BC1 and BC2 offspring. The number of recombinant chromosomes ranged from 3 to 8 in BC1 and from 1 to 7 in BC2 progenies. All recombinant chromosomes possessed mostly a single recombinant segment derived from either a single crossover event or in a few cases double crossover events. This explains the fact that, unlike the situation in most F1 hybrids of other plant species, certain genotypes of Darwin hybrid tulips behave like normal diploid plants producing haploid gametes and give rise to mostly diploid sporophytes.

Establishment of the genomic in situ hybridization (GISH) technique for analysis in interspecific hybrids of Passiflora

“…Hybrids BC 1 HD18-106 and HD18-113 showed different numbers of recombinant chromosomes, denoting variation in the meiotic recombination amongst homeologous chromosomes in HD13 hybrids. A wide variation in the quantity of recombinant chromosomes is commonly reported in the hybrids BC 1 and BC 2 (Marasek-Ciolakowska et al, 2012). GISH is also used in the analysis of recombination in meiotic chromosomes (Lim et al, 2000a).…”

“…Besides confirming the hybrid character, GISH allowed the observation of recombinant chromosomes in backcrossed hybrids (BC 1 ). The use of GISH to identify natural hybrids, to confirm artificial hybridization (Marasek et al, 2004;Contreras et al, 2012), and to identify recombined chromosomes in backcrossed progenies BC 1 and BC 2 (Karlov et al, 1999;Lim et al, 2000b;Marasek-Ciolakowska et al, 2012) has been widely reported for different plant groups. Hybrids BC 1 HD18-106 and HD18-113 showed different numbers of recombinant chromosomes, denoting variation in the meiotic recombination amongst homeologous chromosomes in HD13 hybrids.…”

“…Nevertheless, as revealed in this study, small fragments (<100 bp) were obtained with the simple use of an autoclave for 5 min at 120°C, showing the need to adjust the DNA fragmentation method. DNA cleavage by autoclaving can be influenced by parameters such as temperature, fragmentation time, final volume, and autoclave model; there is a large variation in fragment sizes relative to the time of fragmentation (Jauhar and Peterson, 2006;Marasek-Ciolakowska et al, 2012;Brammer et al, 2013).…”

“…Some methods proposed for GISH apply two different methods for the cleavage of genomic DNA: one directed to the cleavage of DNA for probes and another for blocking DNA, wherein sonication is generally used to cleave the DNA for the probe, and the autoclave is used to cleave the blocking DNA (Jauhar and Peterson, 2006;Marasek-Ciolakowska et al, 2012). Various reports on the use of autoclaving as a sole DNA cleavage method either in the preparation of probes or in the direct use as blocking DNA suggest that autoclaving is an efficient method of DNA fragmentation (Lim et al, 2004;Brammer et al, 2013).…”

Review Genomic in situ hybridization in plants

“…Twentythree F 1 hybrids, 14 RC1, and 32 RC2 were used; all plants used were diploids (2n = 2x = 24), with the exception of plant BC2 (tetrapoid, 2n = 4x = 48) and plant BC2 (aneuploid, 2n = 2x +1 = 25). GISH could distinguish the genomes from both ancestors and the intergenomic recombinations (Marasek-Ciolakowska et al, 2012).…”