Characterisation of distant Alstroemeria hybrids: application of highly repetitive DNA sequences from A. ligtu spp. ligtu
Shujun Zhou, ; Jeu, M.J. de; Visser, R.G.F. ; Kuipers, A.G.J. - \ 2003
Annals of Applied Biology 142 (2003)3. - ISSN 0003-4746 - p. 277 - 283.
in-situ hybridization - molecular cytogenetics - interspecific hybrids - physical organization - ovule culture - sequences - heterochromatin - localization - family - aurea
Clones from a Sau3A family of eight highly repetitive sequences previously isolated from a genomic DNA library of Alstroemeria ligtu ssp. ligtu were sequenced and found to be highly conserved. A trinucleotide microsatellite repeat [GCA](3-4) was present. A second, unrelated, Sau3A repeat was also characterised. Southern analysis proved that the isolated repeats were specific for the A. ligtu subspecies and could not be detected in other Chilean or Brazilean Alstroemeria species. As shown by in situ hybridisation, the Sau3A family and the unrelated Sau3A repeat co-localised at distinct sites along most chromosomes of Alstroemeria ligtu ssp. ligtu and Alstroemeria ligtu ssp. simsii. The present set of species-specific repetitive sequences enables the identification of A. ligtu chromosomes, and thus the tracking of chromosome transmission to interspecific hybrids and their progeny.
Occurrence of numerically unreduced (2n) gametes in Alstroemeria interspecific hybrids and their significance for sexual polyploidization
Ramanna, M.S. ; Kuipers, G. ; Jacobsen, E. - \ 2003
Euphytica 133 (2003)1. - ISSN 0014-2336 - p. 95 - 106.
in-situ hybridization - chromosome arm 1rs - controlled introgression - molecular cytogenetics - ovule culture - wheat - genome - avena - allosyndesis - recombinants
The F1 hybrids of seven diploid Alstroemeria species (2n=2x=16) were investigated for the production of numerically unreduced (2n) gametes and their mode of origin. Based on a survey of 17 interspecific hybrid combinations, consisting of 119 genotypes, it was found that the F1 hybrids of Chilean-Brazilian species mostly produced first division restitution (FDR) 2n gametes. These F1 hybrids were self-pollinated in order to obtain F2 seeds, which was an indication that the F1 plants also produced 2n eggs simultaneously. All the F2 progeny plants were typical allotetraploids, most of which formed 16 bivalents and a small proportion formed multivalents during metaphase I stages of meiosis. Through genomic in situ hybridisation (GISH) it was proved that multivalent formation in F2 plants, derived from A. inodora x A. pelegrina hybrid, was due to homoeologous recombination but not from reciprocal translocations. In order to test the segregation pattern of the recombinant chromosomes, an F3 population from one genotype, P6C49-6, was investigated. The recombinant chromosomes assorted independently from each other supporting the hypothesis that the segregation of chromosomes in ring quadrivalents did not behave like those in translocation heterozygotes. It was concluded that in allopolyploids of Alstroemeria, bilateral sexual polyploidisation could accomplish genetic recombination by both homoeologous crossing-over as well as through the assortment of chromosomes.
Relevance of sexual polyploidization for crop improvement - A review
Ramanna, M.S. ; Jacobsen, E. - \ 2003
Euphytica 133 (2003)1. - ISSN 0014-2336 - p. 3 - 18.
in-situ hybridization - solanum-tuberosum l - gossypium-hirsutum l - 2n pollen formation - division restitution - festuca-pratensis - molecular cytogenetics - homoeologous recombination - aegilops-squarrosa - lolium-multiflorum
Colchicine induced polyploids have not directly contributed for crop improvement in the past. On the other hand, the so-called natural polyploids, derived from the functioning of numerically unreduced (2n) gametes have been shown to be more relevant for crop improvement in many cases. Different types of cytological abnormalities during meiosis can give rise to 2n gametes and the genetic composition of these gametes is variable. Depending on the type meiotic abnormalities, various types of 2n gametes, such as first division restitution (FDR), second division restitution (SDR), indeterminate meiotic restitution (IMR) and post meiotic restitution (PMR) gametes, among, others. have been described in recent years. For the improvement of autopolyploids such as potato, alfalfa, Vaccinium spp., and some of the fodder grasses, FDR gametes have been proved to be highly useful. However, the use of 2n gametes for the improvement of allopolyploid crops has received much less attention so far. Some of the investigations on allopolyploids, derived from Festuca-Lolium, Alstroemeria and Lilium species hybrids, have revealed that 2n gametes can be most useful for the introgression of alien genes and chromosomes into cultivars. An important feature of using sexual polyploidization in the case of allopolyploids is that introgression can be achieved through recombination due to genetic crossing-over between alien chromosomes as well as addition of alien chromosomes, which is extremely difficult or impossible to achieve in the case of colchicine induced allopolyploids. Because of the recent developments in the field of plant molecular biology, methods have become available for the analysis of 2n gametes and sexual polyploid progenies more accurately and to develop systematic breeding approaches. The methods include DNA in situ hybridization (GISH and FISH) and molecular mapping (AFLP, RFLP, RAPDs). In addition to providing basic information on the genetic and genome composition of the polyploid progenies, these methods can be potentially useful for a more efficient creation of desirable breeding material and cultivars.