- Laboratory of Plant Breeding (17)
- PRI Biodiversity and Breeding (17)
- Plant Breeding (17)
- EPS-4 (10)
- EPS (1)
- Lim Ki-Byung (1)
- K.B. Lim (8)
- A.C. Lokker (1)
- A.R. Marasek Ciolakowska (1)
- C.T. Miller (2)
- M. Nadeem Khan (2)
- M.S. Ramanna (16)
- A. Shahin (1)
- T.M. Shen (1)
- A.A. Silfhout van (2)
- J.M. Tuyl van (16)
- R.G.F. Visser (5)
- S.L. Xie (1)
- Shujun Zhou (5)
Tuyl, J.M. van; Arens, P. ; Ramanna, M.S. ; Shahin, A. ; Khan, S.A. ; Xie, S.L. ; Marasek Ciolakowska, A.R. ; Lim, K.B. ; Barba Gonzalez, R. - \ 2011
In: Wild Crop Relatives: Genomic and Breeding Resources, Plantation and Ornamental Crops / Kole, C., Springer Verlag - ISBN 9783642212000 - p. 161 - 184.
Relevance of unilateral and bilateral sexual polyploidization in relation to intergenomic recombination and introgression in Lilium species hybrids
Nadeem Khan, M. ; Barba Gonzalez, R. ; Ramanna, M.S. ; Arens, P.F.P. ; Visser, R.G.F. ; Tuyl, J.M. van - \ 2010
Euphytica 171 (2010)2. - ISSN 0014-2336 - p. 157 - 173.
2n pollen formation - x asiatic hybrids - cytological mechanism - tetraploid progeny - genome composition - diploid potato - distant hybrid - bc2 progenies - gish analysis - lily hybrids
Sexual polyploids were induced in diploid (2n = 2x = 24) interspecific F1 hybrids of Longiflorum × Asiatic (LA) and Oriental × Asiatic (OA) Lilium hybrids by backcrossing to Asiatic (AA) parents as well as by sib-mating of the F1 LA hybrids. A majority of the BC1 progenies were triploid and the progenies from sib-mating were tetraploid or near tetraploids. Genomic in situ hybridization (GISH) technique was applied to assess the intergenomic recombination in the BC1 populations of LA and OA hybrids obtained after unilateral sexual polyploidization. A total of 63 LA (LA × AA and AA × LA) and 53 OA hybrids were analysed. LA hybrids were originated through the functioning of 2n gametes either as 2n eggs or 2n pollen while those of OA hybrids originated through functional 2n pollen of diploid OA genotype. In both type of crosses, a majority of the progenies had originated through First Division Restitution (FDR) mechanism of functional 2n gamete either with or without a cross over. However, there were nine LA- and four OA-genotypes where Indeterminate Meiotic Restitution (IMR) was the mechanism of 2n gamete formation. Based on GISH, total amount of introgression of Longiflorum and Oriental genome into Asiatic genome was determined. Most of the BC progenies exhibited recombination and the amount of recombination was higher in LA hybrids as compared to OA hybrids. Intergenomic recombination was also determined cytologically in the 16 plants of sib-mated LA hybrids where both parents had contributed 2n gametes. Based on these results the nature of interspecific lily hybrids obtained from uni- and bilateral sexual polyploidization leading to allotriploid and allotetraploid formation is discussed in the context of introgression and intergenomic recombination
Construction of chromosomal recombination maps of three genomes of lilies (Lilium) based on GISH analysis.
Nadeem Khan, M. ; Shujun Zhou, ; Barba Gonzalez, R. ; Ramanna, M.S. ; Visser, R.G.F. ; Tuyl, J.M. van - \ 2009
Genome 52 (2009)3. - ISSN 0831-2796 - p. 238 - 251.
in-situ hybridization - genetic-linkage maps - nuclear-dna amounts - x asiatic hybrids - translocation breakpoints - intergenomic recombination - homoeologous recombination - sexual polyploidization - interspecific hybrids - arabidopsis-thaliana
Chromosomal recombination maps were constructed for three genomes of lily (Lilium) using GISH analyses. For this purpose, the backcross (BC) progenies of two diploid (2n = 2x = 24) interspecific hybrids of lily, viz. Longiflorum × Asiatic (LA) and Oriental × Asiatic (OA), were used. Mostly the BC progenies of LA hybrids consisted of both triploid (2n = 3x = 36) and diploid (2n = 2x = 24) with some aneuploid genotypes and those of OA hybrids consisted of triploid (2n = 3x = 36) and some aneuploid genotypes. In all cases, it was possible to identify the homoeologous recombinant chromosomes as well as accurately count the number of crossover points, which are called ¿recombination sites¿. Recombination sites were estimated in the BC progeny of 71 LA and 41 OA genotypes. In the case of BC progenies of LA hybrids, 248 recombination sites were cytologically localized on 12 different chromosomes of each genome (i.e., L and A). Similarly, 116 recombinant sites were localized on the 12 chromosomes each from the BC progenies of OA hybrids (O and A genomes). Cytological maps were constructed on the basis of the percentages of distances (micrometres) of the recombination sites from the centromeres. Since an Asiatic parent was involved in both hybrids, viz. LA and OA, two maps were constructed for the A genome that were indicated as Asiatic (L) and Asiatic (O). The other two maps were Longiflorum (A) and Oriental (A). Remarkably, the recombination sites were highly unevenly distributed among the different chromosomes of all four maps. Because the recombination sites can be unequivocally identified through GISH, they serve as reliable landmarks and pave the way for assigning molecular markers or desirable genes to chromosomes of Lilium and also monitor introgression of alien segments
|Interspecific hybridization in lily (Lilium): Interploidy crosses involving interspecific F1 hybrids and their progenies
Shujun Zhou, ; Barba Gonzalez, R. ; Lim, K.B. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2008
In: Floriculture, ornamental and plant biotechnology: advances and topical issues Vol 5 Global Science Books (Floriculture, ornamental and plant biotechnology: advances and topical issues 5) - ISBN 9784903313122 - p. 152 - 156.
Despite a long history of cultivation, a large number of lily (Lilium) cultivars were still diploid (2n=2x=24) till recently. But polyploid cultivars are rapidly increasing. In addition to having robust stems, large flowers, thicker and larger leaves, polyploids can also serve to combine desirable characters from species of different taxonomic sections; not only from the cultivated groups, viz., Sinomartagon, Archelirion and Leucolirion, but also from sections that include non-cultivated species. Because the F1 hybrids between the species of different taxonomic sections are highly sterile, it is imperative that breeding has to be carried out at the polyploidy level. This chapter is based on our results on using intersectional interspecific hybrids of Longiflorum x Asiatic (LA) and Oriental x Asiatic (OA) groups of lilies and their polyploid backcross progenies BC1, BC2 and BC3). In order to cross genotypes of different ploidy levels, i.e., interploidy crosses, a knowledge of embryo and endosperm ploidy levels is valuable because, unlike in most other plant species, lily has very large chromosomes and the embryo sac formation is of tetrasporic 8-nucleate type. In order to highlight the differences, a comparison is made with the most commonly occurring, monosporic 8-nucleate type of diploid potato, with 24 chromosomes (same as lily). Some of the limitations and constraints associated with interploidy crossing are considered
|Interspecific hybridization in lily: the use of 2n-gametes in interspecific lily hybrids
Barba Gonzalez, R. ; Lim, K.B. ; Shujun Zhou, ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2008
In: Floriculture, ornamental and plant biotechnology: advances and topical issues Vol 5 Global Science Books (Floriculture, ornamental and plant biotechnology: advances and topical issues 5) - ISBN 9784903313122 - p. 146 - 151.
Lily comprises more than 80 species belonging to 7 sections. Within the sections cultivars bred from Sinomartagon, Archelirion, and Leucolirion are the most important in the commercial market. At this moment, the most promising breakthrough in lily breeding is the raising of new cultivar through interspecific hybridization with introgression of useful genetic traits from species or breeding materials belonging to the wild species which are not commonly used so far for commercial breeding. We have been crossing almost all different cross combinations and have succeeded in more than 28 cross combinations since 1980. The F1 hybrids between the species have shown the intermediate phenotypic characteristics. Making interspecific or intergeneric hybrid is laborious but finding the clues, affecting to the most successful embryo formation, and growth is even more difficult and time consuming. Therefore research on the successful interspecific hybridization between distantly related species was carried out at several laboratories in the world. For the successful interspecific hybridization breeding, not only production of F1 interspecific hybrids but also successful production of subsequent generations using interspecific hybrids to introgress valuable trait(s) is important. One of the promising crosses is of course between Orientals and several species such as L. henryi, Asiatics, and trumpet lilies. In this context, we demonstrate the possible methods and some valuable instances of the interspecific hybridization in lilies
|Interspecific hybridization in Lily (Lilium): Taxonomic and commercial aspects of using species hybrids in breeding
Lim, K.B. ; Barba Gonzalez, R. ; Shujun Zhou, ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2007
In: Floriculture, ornamental and plant biotechnology: advances and topical issues Vol 5 Global Science Books (Floriculture, ornamental and plant biotechnology: advances and topical issues 5) - ISBN 9784903313122 - p. 138 - 145.
With the main goal of generating new groups of lilies, that combine agronomic characteristics of major importance, a large number of crosses were performed among the three most important groups of lilies (Lilium), viz., Asiatic, Longiflorum and Oriental; and to some species, to produce F1 inter-specific hybrids. These hybrids, as well as many other F1 hybrids, were sterile and two approaches were used to overcome sterility: i) chromosome doubling through chemicals and ii) the use of naturally occurring or induced unreduced (2n) gametes. The first approach produced many fertile hybrids, however, due to autosyndetic pairing in the allotetraploids, recombination was not detected through DNA in situ hybridization techniques (GISH), and introgression was not achieved. On the other hand, through extensive meiotic analyses and pollen germination tests, we selected hybrids that were able to produce 2n gametes, and in some cases, hybrids in which 2n gametes could be induced. Many plants were obtained in reciprocal backcrosses and recombination as well as introgression was detected through GISH and FISH analyses. In this chapter we present the success in breeding lilies from different taxonomical sections through the use of naturally occurring and induced 2n gametes. The mechanisms of 2n gamete formation are described and the genetic considerations of their use to achieve introgression and to generate variability are examined.
Induction og 2n gametes for overcoming F1-sterility in lily and tulip
Barba Gonzalez, R. ; Miller, C.T. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2006
Acta Horticulturae 714 (2006). - ISSN 0567-7572 - p. 99 - 106.
For overcoming F1-sterility in interspecific hybrids, mitotic and meiotic polyploidisation is applied in lily and can result in fertile allopolyploids. The mechanism of viable pollen production of mitotic and meiotic polyploidisation is quite different. Mitotic polyploids are obtained by artificial chromosome doubling and results in normal pairing of homologous chromosome set, which enables the formation of 2x gametes during the meiosis. Meiotic polyploidisation, on the other hand, leads in rare cases of restitutional chromosome division, to the formation of unreduced gametes (2n gametes). In contrast to mitotic doubling, homoeologous recombination can occur in these gametes. Genomic in situ hybridization (GISH) was used to discriminate parental chromosomes in the F1 hybrids and backcross progenies to detect homoeologous recombination. Mitotic polyploidisation showed no homoeologous recombinations between the parental genomes whereas in meiotic polyploids it was detected in a high frequency. The use of 2n gametes is therefore the most promising approach for the introgression of desirable characters in using interspecific hybrids in breeding. In both cases, the frequency of viable gametes appeared to be low and limited to a few F1-hybrids. A new and promising method is developed in which 2n-gametes can be induced by the application of laughing gas (N2O). This method proved to be successful in lily and the occurrence of homoeologous recombination, a characteristic of meiotic polyploidisation, was detected. In tulip where the production of mitotic polyploids requires at least five years, it will speed up breeding with interspecific hybrids enormously
Progenies of allotriploids of Oriental x Asiatic lilies (Lilium) examined by GISH analysis
Barba Gonzalez, R. ; Silfhout, A.A. van; Visser, R.G.F. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2006
Euphytica 151 (2006)2. - ISSN 0014-2336 - p. 243 - 250.
nuclear-dna amounts - lily hybrids - crosses - recombination - culture - angiosperms - narcissus - liliaceae
With the aim of utilizing allotriploid (2n = 3x = 36) lily hybrids (Lilium) in introgression breeding, different types of crosses were made. First, using diploid Asiatic lilies (2n = 2x = 24), reciprocal crosses (3x ¿ 2x and 2x ¿ 3x) were made with allotriploid hybrids (AOA) obtained by backcrosses of F1 Oriental × Asiatic hybrids (OA) to Asiatic cultivars (A). Secondly, the AOA allotriploids were crossed with allotetraploid (OAOA, 2n = 4x = 48), in 3x ¿ 4x combination. Finally, the AOA allotriploids where crossed to 2n gamete producer F1 OA hybrids (3x ¿ 2x (2n)). Two types of triploids were used as parents in the different types of crosses, derived from: (a) mitotic polyploidization and (b) sexual polyploidization. Ploidy level of the progeny was determined by estimating the DNA values through flowcytometry as well as chromosome counting. The aneuploid progeny plants from 3x ¿ 2x and reciprocal crosses had approximate diploid levels and in 3x ¿ 4x crosses and 3x ¿ 2x (2n) the progeny had approximate tetraploid levels. Balanced euploid gametes (x, 2x and 3x) were formed in the AOA genotypes. Recombinant chromosomes were found in the progenies of all crosses, except in the case of 2x ¿ 3x crosses through genomic in situ hybridization (GISH) analyses. Recombinant chromosomes occurred in the F1 OA hybrid when the triploid AOA hybrid was derived through sexual polyploidization, but not through mitotic polyploidization with two exceptions. Those recombinant chromosomes were transmitted to the progenies in variable frequencies.
Nitrous oxide N2O incudes 2n gametes in sterile F1 hybrids of Oriental x Asiatic lilies (Lilium) and leads to intergenomic recombination
Barba Gonzalez, R. ; Miller, C.T. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2006
Euphytica 148 (2006)3. - ISSN 0014-2336 - p. 303 - 309.
in-situ hybridization - sexual polyploidization - interspecific hybrids - aneuploids - gish
Eight different genotypes of the F1 hybrids between Oriental × Asiatic lily (Lilium) hybrids (2n = 2x = 24) were treated with nitrous oxide (N2O) gas under pressure for 24 and 48 hours. At the time of treatment, all plants possessed early meiotic stages in the anthers of the oldest flower buds. The mature flowers from treated plants were monitored for fertility through pollen germination in vitro as well as by using them in crosses with diploid Asiatic hybrids (2n = 2x = 24) both as male and female parents. In five out of the eight genotypes of OA hybrids there was evidence for the production of 2n pollen which germinated in vitro from either one or both treatments. The 2n pollen from three genotypes was successfully used in crosses. In two cases, the treated plants were successfully used as female parents which indicated the formation of 2n (or 2x) egg cells. From an analysis of 41 sexual polyploid progenies obtained from N2O treated plants it was shown that they were all euploids consisting of 34 triploids (2n = 3x = 36) and seven tetraploids (2n = 4x = 48). A detailed cytological analysis of 12 progeny plants through genomic in situ hybridization (GISH) proved that N2O had induced first division restitution gametes in most cases and in two cases they produced gametes through indeterminate meiotic restitution. There was evidence for intergenomic recombination in three cases.
Meiotic polyploidization with homoeologous recombination induced by caffeine treatment in interspecific lily hybrids
Lim, K.B. ; Barba Gonzalez, R. ; Shujun Zhou, ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2005
Korean Journal of Genetics 27 (2005)3. - ISSN 0254-5934 - p. 219 - 226.
lilium hybrids - bc2 progenies - restitution - cytokinesis - gish
Caffeine solution was injected into the flower bud to recover F, fertility of the intersectional diploid Lilium species hybrid (2n=2x=24). 0.3% of caffeine solution was the most effective concentration to produce fertile 2n-gametes. The male and female gametes had a range of fertility following caffeine injection in relation to the different sizes of flower buds. The gametes from the treated OA-hybrids showed to be fertile. They were crossed both as male and female parents to the Asiatics, and produced 279 BC, progeny plants. Flowcytometric and chromosomal observation confirmed that all progenies were triploid (2n=3x=36), indicating that the 2n-gametes from the OA-hybrid were functional following caffeine treatment. There was no homoeologous recombination between parental species in the progeny derived from male gametes of the OA-hybrid. However, three plants originating from the female gametes showed homoeologous recombination between Oriental and Asiatic genomes. The functional female gametes were produced when treated at the range of 20-23mm and 34-37mm of flower bud length. Based on the chromosome constitution of the triploid BC1 progenies, it was concluded that FDR 2n-gamete was functional and homoeologous recombination had occurred during the origin of 2n gametes.
Intergenomic recombination in F1 lily hybrids (Lilium) and its significance for genetic variation in the BC1 progenies as revealed by GISH and FISH
Barba Gonzalez, R. ; Ramanna, M.S. ; Visser, R.G.F. ; Tuyl, J.M. van - \ 2005
Genome 48 (2005)5. - ISSN 0831-2796 - p. 884 - 894.
bc2 progenies - crosses - pollination - relevance - culture - probe - pcr
Intergenomic recombination was assessed in a BC1 population of Oriental (O) × Asiatic (A) lilies (Lilium) backcrossed to Asiatic parents. This population consisted of 38 plants generated from the 2n gametes from 2 genotypes (951502-1 and 952400-1) of the diploid F1, Oriental × Asiatic lilies (2n = 2x = 24) as parents. In the majority of BC1 plants, there was evidence that first division restitution, with and without crossovers, resulted in functional gametes. However, there were 5 BC1 plants in which 2n gametes originated from indeterminate meiotic restitution (IMR). Based on the number of recombinant chromosomes for a particular homoeologous pair, 3 types of plants were identified: (i) those with both the reciprocal product of a crossover (O/A, A/O, where O represents the centromere of the O genome and A the recombinant segment of Asiatic chromosome, and vice versa); (ii) those with 1 normal chromosome of the O genome and a recombinant chromosome (O, A/O); and (iii) those with 1 normal chromosome of the A genome and a recombinant chromosome (A, O/A). An important feature of A × OA backcross progeny is the occurrence of substitutions for the segment distal in the crossover wherever the recombinant chromosome O/A was present. In the case of IMR, the substitution occurred for both proximal and distal recombinant segments. The significance of these substitutions is that they offer the potential for the phenotypic expression of recessive genes in polyploids (i.e., nulliplex genotype)
The use of 2n gametes for introgression breeding in Oriental x Asiatic lilies
Barba Gonzalez, R. - \ 2005
Wageningen University. Promotor(en): Richard Visser, co-promotor(en): Jaap van Tuyl. - Wageningen : S.n. - ISBN 9085042682 - 111
lilium - plantenveredeling - introgressie - gameten - hybriden - ploïdie - genetische variatie - chromosoomtransmissie - lilium - plant breeding - introgression - gametes - hybrids - ploidy - genetic variation - chromosome transmission
Occurrence of 2n gametes in the F1 hybrids of Oriental x Asiatic lilies (Lilium): Relevance to intergenomic recombination and backcrossing
Barba Gonzalez, R. ; Lim, K.B. ; Ramanna, M.S. ; Visser, R.G.F. ; Tuyl, J.M. van - \ 2005
Euphytica 143 (2005)1-2. - ISSN 0014-2336 - p. 67 - 73.
in-situ hybridization - aegilops-squarrosa - sexual polyploidization - interspecific hybrids - restitution - mechanisms - crosses - gish - rye
Cytological modes of the origin of 2n gametes were investigated in six different genotypes of F1 hybrids between Oriental and Asiatic (OA) lilies (Lilium, 2n = 2x = 24). Chromosome pairing between the parental genomes was very low, the average frequency range from 0.3 to 1.2 bivalents per cell among the genotypes. Within a genotype the frequency of bivalents varied from 0 to 6 in some cases. The normally occurring haploid pollen grains were totally sterile. In contrast, in different genotypes, variable percentages of 2n pollen were found and shown to be fertile as estimated from pollen germination. A cytological analysis of Metaphase I and subsequent stages of meiosis using genomic in situ hybridization (GISH) revealed that there was intergenomic recombination between the alien genomes. Following Metaphase I stage, three different types of abnormal cytological events led to the formation of 2n pollen: (i) Post-Metaphase I division (PMI), (ii) Post-Metaphase II division (PMII) and (iii) Asymmetric Cytokinesis of the pollen mother cell followed by chromosome division. All three cytological events led to first division restitution (FDR) gametes. Based on in vitro pollen germination it was proved for two genotypes that 2n pollen was viable only during the first day of anthesis. It was possible to use 2n pollen successfully for backcrossing. Implications of 2n pollen for intergenomic recombination in BC1 progenies are discussed
Use of 2n gametes for inducing intergenomic recombination in lily hybrids
Barba Gonzalez, R. ; Lim, K.B. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2004
Acta Horticulturae 673 (2004). - ISSN 0567-7572 - p. 161 - 166.
Genetic recombination is an important pre-requisite for transferring specific genetic traits across distantly related plant species. With a view to transfer some of the desirable characters like resistances against viruses, Fusarium and Botrytis, besides many horticultural traits, we have made interspecific hybrids between different species of lilies (Lilium, 2n=2x=24). The F1 hybrids in all these cases are totally sterile because of the lack of chromosome pairing. Traditional method of somatic chromosome doubling (mitotic polyploidization) can produce fertile allotetraploids. But, because of strict autosyndetic pairing in allotetraploids, no genetic recombination occurs in the progenies. In order to overcome this difficulty, we have selected 2n gamete producing F1 hybrids of different Lilium species and used them successfully for sexual polyploidization (meiotic polyploidization). An important feature of meiosis in the F1 hybrids is that a certain amount of homoeologous chromosome pairing does occur in them. When 2n gametes originate from such F1 hybrids through first division restitution (FDR) they are expected to possess recombinant chromosomes. Cytological analyses, using genomic in situ hybridization (GISH), of the sexual polyploid progenies have proved that considerable amount of intergenomic recombinant chromosomes can be recovered in the chromosome complements. One example of the sexual polyploid progenies from Oriental x Asiatic hybrid lilies possessing intergenomic recombinant chromosomes will be illustrated and discussed.
Occurrence of SDR 2N-gametes in Lilium hybrids
Lim, K.B. ; Shen, T.M. ; Barba Gonzalez, R. ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2004
Breeding Science 54 (2004)1. - ISSN 1344-7610 - p. 13 - 18.
interspecific hybrids - bc2 progenies - potato - mutants - desynapsis - fertility - crosses - pollen - gish
The mechanism of SDR 2n-pollen formation was analyzed in two intra-sectional diploid (2n = 2x = 24) Lilium hybrids (Enchantment x L. pumilum). Variable frequencies of 2n-pollen were found. Meiotic analysis indicated that the intra-sectional hybrids showed perfect chromosome pairing in most cases at metaphase I and normal anaphase I movement of pollen mother cells (PMCs), but produced 2n-pollen by second division restitution (SDR). A high bivalent formation (11.9II and 11.8II, respectively) at metaphase 1, irregular meiotic division such as unbalanced chromosome separation and chromatic fragmentation resulted yet in acceptable pollen fertility for cross-pollination. The hybrids were fertile, and when used as male parents, offspring could tie generated. The significance of the occurrence of 2n-pollen for the breeding of lilies was analyzed.
Mitotic and meiotic polyploidization in lily hybrids for transferring Botrytis resistance
Beers, C.M. ; Barba Gonzalez, R. ; Silfhout, A.A. van; Ramanna, M.S. ; Tuyl, J.M. van - \ 2004
Acta Horticulturae 673 (2004). - ISSN 0567-7572 - p. 449 - 452.
In an effort to transfer Botrytis resistance from Oriental lilies to Asiatic hybrids (Lilium, 2n=2x=24) we made a large number of F1 hybrids between these two distantly related species. Because these species belong to two different taxonomic sections, the F1 hybrids were totally sterile and could not be directly used in breeding. Therefore, two approaches were used for utilizing the F1 hybrids. First, the somatic chromosome number of the F1s was doubled by treating with oryzalin that resulted in allotetraploids (mitotic doubling). These allotetraploids were used for crossing with the parents. Second, 2n gametes were used directly for crossing with the parents for producing sexual polyploids (meiotic doubling). The two types of BC1 progenies were monitored for resistance against Botrytis elliptica through a ¿leaf tip test¿. Disease severity was evaluated on a nominal scale, ranging from 1 resistant (no lesions) to 6 (a high degree of necrosis with mycelium or even spores). In both populations the resistance varied from very susceptible to highly resistant. However, the occurrence of transgression of resistance, meaning that the degree of resistance in some seedlings exceeded that of the parent, was higher in meiotically doubled polyploids as compared to those derived from mitotic doubling. This was explained from the fact that the typical allotetraploids produce uniformly a single genotype of 2x gametes containing both parental genomes because of autosyndetic pairing so that there is no scope for genetic variation. On the contrary, in the case of meiotic polyploids intergenomic recombination occurs between the alien chromosomes that could lead to considerable amount of genetic variation. This phenomenon might be an explanation for the observed transgression of Botrytis resistance in the meiotic polyploid progenies.
Use of 2n gametes for the production of sexual polyploids from sterile Oriental x Asiatic hybrids of lilies (Lilium)
Barba Gonzalez, R. ; Lokker, A.C. ; Lim Ki-Byung, ; Ramanna, M.S. ; Tuyl, J.M. van - \ 2004
Theoretical and Applied Genetics 109 (2004)6. - ISSN 0040-5752 - p. 1125 - 1132.
situ hybridization gish - interspecific hybrids - homoeologous recombination - aegilops-squarrosa - bc2 progenies - alstroemeria - crosses - culture - restitution - chromosomes
Sixteen Oriental and 12 Asiatic cultivars were crossed in 158 different combinations. A total of 708 F1 hybrids were obtained from 86 of the different combinations of 15 Oriental and 11 Asiatic cultivars. Because the Lilium cultivars (2n=2x=24) used for the production of these hybrids belong to two different taxonomic sections-Archelirion (O) and Sinomartagon (A), respectively - the F1 hybrids (OA) could be obtained only through embryo, embryo sac rescue, ovary slice or ovule culture. Most of the F1 hybrids were highly sterile (did not produce viable n gametes) due to the failure of chromosome pairing. However, in a few cases F1 plants were found that produced viable 2n pollen at variable frequencies. These 2n pollen grains were successfully used for the production of backcross progenies. Using genomic in situ hybridization we found intergenomic recombinant chromosomes in the sexual polyploid progenies. These results indicate that there are effective prospects for combining important horticultural traits from the two main groups of cultivars of lilies through sexual polyploidization