RESUMO
ABSTRACT Plant genetic resources for food and agriculture are ex situ conserved in germplasm banks as samples (accessions) of natural or naturalized populations, either as the originally sampled propagules (mainly seeds) or their multiplications. The premises underlying ex situ conservation are that (a) it is the safest and cheapest alternative for germplasm preservation for future generations and (b) accessions are representative of the genetic diversity encountered in nature. In the past decades, ideas, alternatives and considerations have been put forward on the topic, and protocols have been devised for plant germplasm sampling, conservation and multiplication. However, limitations in the management efficiency of germplasm banks have been pointed out by international organizations. In our opinion, germplasm banks in general need to revise their functioning and management at the light of principles and methods of Genetics. To that end, it is necessary to consider the reproductive biology of higher plants -whose genetic consequences at both the individual plant and the population levels are not always either fully understood or taken into account in devising the protocols-, the genetic structures of wild and cultivated populations, and the course of the genetic material in the populations. In this paper, we discuss the three topics and provide an example of a national forage breeding program, from germplasm bank accessions as the germplasm of origin to the obtainment of commercial cultivars. Finally, we present a proposal as a base for discussion among curators, researchers and breeders.
RESUMEN Los recursos genéticos vegetales para la alimentación y la agricultura se conservan ex situ en bancos de germoplasma como muestras (introducciones) de poblaciones naturales o naturalizadas ya sea como propágulos originales (mayoritariamente semillas) o sus multiplicaciones. Las premisas subyacentes son que (a) es la alternativa más segura y barata de preservación de germoplasma para futuras generaciones y (b) las introducciones son representativas de la diversidad genética que se encuentra en la naturaleza En las últimas décadas, se han presentado ideas, alternativas y consideraciones sobre el tema y se han elaborado protocolos para el muestreo, conservación y multiplicación de germoplasma. Sin embargo, organizaciones internacionales han señalado limitaciones en la eficiencia del manejo de los bancos de germoplasma. En nuestra opinión, se necesita revisar el funcionamiento y manejo de dichos bancos en general a la luz de los principios y métodos de Genética. Para tal fin, es necesario considerar la biología reproductiva de las plantas superiores -cuyas consecuencias genéticas a nivel de planta individual y de población no se comprenden en su totalidad o no se consideran al idear los protocolos -, las estructuras genéticas de poblaciones naturales y cultivadas, y el curso del material genético en las poblaciones. En este trabajo discutimos los tres temas y proveemos un ejemplo de un programa nacional de mejoramiento de forrajeras, desde las introducciones como germoplasma de origen hasta la obtención de cultivares comerciales. Finalmente, presentamos una propuesta como base de discusión entre curadores, investigadores y mejoradores.
RESUMO
Stevia rebaudiana (Bertoni) Bertoni (2n=2x=22) (Asteraceae family) is a species of economic value due to the presence of steviol glycosides in leaves -mainly stevioside and rebaudioside A- which are non-caloric sugars. In 2013, a collection of plants (genotypes) from four contrasting environments was established in Tucuman, Argentina, for evaluation under local conditions and, eventually, breeding purposes. As a first step, pollen viability and meiosis was studied in a sample of 56 plants. The percentage of pollen viability varied from medium (69.4%) to high (99.6%) in 52 of them, but from low (36.5%) to relatively low (51.5%) in the remaining four. The latter four plants also presented pollen grains of heterogeneous size, which were classified as n (normal, the most frequent size in the sample),
Stevia rebaudiana (Bertoni) Bertoni (2n=2x=22) (familia Asteraceae) es una especie de valor economico debido a la presencia de glucosidos de esteviol en sus hojas, principalmente esteviosido y rebaudiosido A, que son azucares no caloricos. En 2013, se establecio una coleccion de plantas (genotipos) provenientes de cuatro ambientes contrastantes en Tucuman, Argentina, para su evaluacion en condiciones locales y, eventualmente, con fines de mejoramiento genetico. Como primer paso, se estudio la viabilidad del polen y la meiosis en una muestra de 56 plantas. El porcentaje de viabilidad del polen fue de medio (69,4%) a alto (99,6%) en 52 de ellas, pero de bajo (36,5%) a relativamente bajo (51,2%) en las cuatro restantes. Las ultimas cuatro plantas tambien presentaron granos de polen de tamano heterogeneo, que se clasificaron como n (normal, el tamano mas frecuente en la muestra),
RESUMO
To investigate the molecular bases of postzygotic hybridization barriers in tuber-bearing Solanums, the wild species Solanum commersonii Dunal ex Poir. (cmm, 2n = 2x = 24, 1EBN) and Solanum acaule Bitter (acl, 2n = 4x = 48, 2EBN) were crossed in intra- and interspecific genotypic combinations, and the transcriptome of immature seeds was analyzed by using the cDNA-AFLP technique. From a total of 423 analyzed cDNA fragments, 107 (25.3%) were differentially regulated in the compatible (acl × acl and cmm × cmm) versus incompatible (acl × cmm) crosses. DNA sequence data were obtained from 21 fragments and RT-PCR analyses were carried out with five fragments to validate the cDNA-AFLP differential pattern. Sequence analysis suggested a possible role for the differentially expressed sequences in cytokinesis, cell cycle, secondary and hormonal metabolism, biodegradation, and transport. In situ hybridization experiments with fragments encoding an ubiquitin-fold modifier 1 precursor and a possible vesicle transport protein revealed expression of these genes in the embryo and endosperm. The results suggest that the collapse of the embryo and endosperm in incompatible crosses may be related to alterations in cell cycle and cytokinesis.
Assuntos
Cruzamentos Genéticos , Solanum/genética , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , Ciclo Celular , DNA Complementar/química , Genótipo , Hibridização Genética , Reação em Cadeia da Polimerase em Tempo Real , Solanum/classificação , Especificidade da EspécieRESUMO
Wild potatoes are native to the Americas, where they present very wide geographical and ecological distribution. Most are diploid, obligate out-crossers due to a multiallelic gametophytic self-incompatibility (S) locus that prevents self-fertilisation and crossing between individuals carrying identical S-alleles. They have two alternative modes of reproduction: sexual (by seeds) and asexual (by stolons and tubers), which provide, respectively, for genetic flexibility in changing environments and high fitness of adapted genotypes under stable conditions. Since the early twentieth century, their taxonomic classification has been mostly based on morphological phenotypes (Taxonomic Species Concept). More recently, attempts have been made to establish phylogenetic relationships, applying molecular tools in samples of populations (accessions) with a previously assigned specific category. However, neither the reproductive biology and breeding relations among spontaneous populations nor the morphological and genetic variability expected in obligate allogamous populations are considered when the taxonomic species concept is applied. In nature, wild potato populations are isolated through external and internal hybridisation barriers; the latter, which are genetically determined, can be either pre-zygotic (pollen-pistil incompatibility) or post-zygotic (abortion of embryo, endosperm or both tissues, sterility, and hybrid weakness and breakdown in segregating generations). The internal barriers, however, can be incomplete, providing opportunities for hybridisation and introgression within and between populations and ploidy levels in areas of overlap. The widespread occurrence of spontaneous hybrids in nature was recognised in the mid-twentieth century. Using genetic approaches, results have been obtained that provide strong support to the assertion that populations are at different stages of genetic divergence and are not at the end of the evolutionary process, as presupposed by the Taxonomic Species Concept. Furthermore, since wild potatoes have uniparental and biparental overlapping generations, the Biological Species Concept - developed for sexually reproducing biparental organisms - cannot be applied to them. In this paper, morphological, genetic, molecular and taxonomic studies in wild potato are reviewed, considering the genetic consequences of their reproductive biology, in an attempt to shed light on the species problem, because of its relevance in germplasm conservation and breeding.
Assuntos
Especiação Genética , Filogenia , Solanum tuberosum/classificação , Solanum tuberosum/genética , Alelos , Cruzamento , Hibridização Genética , Reprodução , Autoincompatibilidade em Angiospermas , Solanum tuberosum/fisiologiaRESUMO
Wild potato species are widely distributed in the Americas, where they spontaneously grow in very diverse habitats. These species - with low chromosome differentiation - form polyploid series with 2n = 2x, 3x, 4x and 6x (x =12). They are isolated in nature by external and internal hybridisation barriers that can be incomplete, allowing hybridisation in areas of sympatry. Nevertheless, most accessions in germplasm banks, regardless of genetic background of the sampled spontaneous populations, have been assigned specific categories based on morphological characters. To further investigate the extent of hybridisation in the group and for comparative purposes, pollen viability was estimated in (i) artificial hybrids between a commercial cultivar (Calén INTA) of the common potato (tetraploid Solanum tuberosum ssp. tuberosum) and the tetraploid cytotype of the related wild species S. gourlayi, and (ii) samples of plants (accessions) and inflorescences of natural populations from Argentina, tentatively classified as 'presumed hybrids' (S. infundibuliforme-S. gourlayi) and 'species' (S. infundibuliforme, S. gourlayi and S. chacoense). Regardless of origin, 98 out of 103 plants analysed had zero to 70% pollen viability (zero to 40% in eight of them). Pollen grains were of variable size and morphology and, in mostly male sterile plants, the only viable pollen grains were 2n and/or 4n. Furthermore, male sterile plants shared various abnormalities in meiosis I and II (unpaired chromosomes, unequal chromosome distribution, precocious/lagging chromosomes, parallel, tripolar, fused and multiple spindles, unequal size nuclei, dyads, triads and pentads in addition to normal tetrads, among others). These results provide novel evidence to support field observations of early potato botanists on the extent of spontaneous hybridisation in wild Argentinian potato populations, which is not reflected in the current taxonomy and has significant consequences for germplasm conservation and breeding.
Assuntos
Meiose/fisiologia , Infertilidade das Plantas/genética , Pólen/genética , Solanum tuberosum/genética , Argentina , Hibridização Genética , Inflorescência/genética , Plantas Geneticamente Modificadas , Ploidias , Pólen/citologia , Pólen/crescimento & desenvolvimento , Pólen/ultraestrutura , Solanum/genética , Solanum tuberosum/citologia , Solanum tuberosum/crescimento & desenvolvimento , Solanum tuberosum/ultraestruturaRESUMO
The Endosperm Balance Number (EBN) is an important concept for potato breeding and has evolutionary importance in tuber-bearing Solanum species. The EBN is part of the post-zygotic hybridization barriers in the group and represents a reproductive isolating mechanism. Few genes have been proposed to be involved in its genetic control; until now, however, neither specific genes nor its molecular basis have been well established. Histological observations of embryo and endosperm development in inter-EBN crosses in tuber-bearing Solanum revealed phenotypes similar to those recently described in Arabidopsis seed mutants. The common feature between them is that the endosperm nuclei become greatly enlarged and that embryos are arrested at the globular stage. The proteins encoded by the Arabidopsis TITAN genes are related to chromosome dynamics and cell division. Based on the sequence of titan mutants, genes in potato species related to cell cycle and microtubule assembly were isolated. In this article a perspective model is proposed to explore the utility of Arabidopsis mutants associated with cell cycle control as a tool to elucidate the molecular basis of EBN in potato. Further research focused on the expression pattern of these genes in intra- and inter-EBN crosses in potato species will be performed.(AU)
Assuntos
Humanos , Animais , Fatores de Ribosilação do ADP/química , Arabidopsis/embriologia , Arabidopsis/genética , Arabidopsis/metabolismo , Fenótipo , Cruzamentos Genéticos , Ploidias , Solanum/embriologia , Solanum/genética , Solanum/metabolismo , Ciclo Celular , Dados de Sequência Molecular , Mutação , Proteínas de Plantas/química , Proteínas de Plantas/genética , Regulação da Expressão Gênica de Plantas , Alinhamento de SequênciaRESUMO
The Endosperm Balance Number (EBN) is an important concept for potato breeding and has evolutionary importance in tuber-bearing Solanum species. The EBN is part of the post-zygotic hybridization barriers in the group and represents a reproductive isolating mechanism. Few genes have been proposed to be involved in its genetic control; until now, however, neither specific genes nor its molecular basis have been well established. Histological observations of embryo and endosperm development in inter-EBN crosses in tuber-bearing Solanum revealed phenotypes similar to those recently described in Arabidopsis seed mutants. The common feature between them is that the endosperm nuclei become greatly enlarged and that embryos are arrested at the globular stage. The proteins encoded by the Arabidopsis TITAN genes are related to chromosome dynamics and cell division. Based on the sequence of titan mutants, genes in potato species related to cell cycle and microtubule assembly were isolated. In this article a perspective model is proposed to explore the utility of Arabidopsis mutants associated with cell cycle control as a tool to elucidate the molecular basis of EBN in potato. Further research focused on the expression pattern of these genes in intra- and inter-EBN crosses in potato species will be performed.
Assuntos
Humanos , Animais , Arabidopsis/embriologia , Arabidopsis/genética , Arabidopsis/metabolismo , Cruzamentos Genéticos , Fatores de Ribosilação do ADP/química , Fenótipo , Ploidias , Solanum/embriologia , Solanum/genética , Solanum/metabolismo , Ciclo Celular , Regulação da Expressão Gênica de Plantas , Dados de Sequência Molecular , Mutação , Proteínas de Plantas/genética , Proteínas de Plantas/química , Alinhamento de SequênciaRESUMO
The Endosperm Balance Number (EBN) is an important concept for potato breeding and has evolutionary importance in tuber-bearing Solanum species. The EBN is part of the post-zygotic hybridization barriers in the group and represents a reproductive isolating mechanism. Few genes have been proposed to be involved in its genetic control; until now, however, neither specific genes nor its molecular basis have been well established. Histological observations of embryo and endosperm development in inter-EBN crosses in tuber-bearing Solanum revealed phenotypes similar to those recently described in Arabidopsis seed mutants. The common feature between them is that the endosperm nuclei become greatly enlarged and that embryos are arrested at the globular stage. The proteins encoded by the Arabidopsis TITAN genes are related to chromosome dynamics and cell division. Based on the sequence of titan mutants, genes in potato species related to cell cycle and microtubule assembly were isolated. In this article a perspective model is proposed to explore the utility of Arabidopsis mutants associated with cell cycle control as a tool to elucidate the molecular basis of EBN in potato. Further research focused on the expression pattern of these genes in intra- and inter-EBN crosses in potato species will be performed.
Assuntos
Arabidopsis/genética , Sementes/citologia , Solanum/genética , Fatores de Ribosilação do ADP/química , Sequência de Aminoácidos , Animais , Arabidopsis/embriologia , Arabidopsis/metabolismo , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Ciclo Celular , Núcleo Celular/metabolismo , Cruzamentos Genéticos , Regulação da Expressão Gênica de Plantas , Humanos , Dados de Sequência Molecular , Mutação , Fenótipo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Ploidias , Alinhamento de Sequência , Solanum/embriologia , Solanum/metabolismoRESUMO
Callus growth and plant regeneration from long-term callus cultures were studied in two elite clones of Asparagus officinalis cv. Argenteuil, to establish a suitable protocol for a prospective in vitro selection program. Callus initiation and growth was evaluated on MS medium with 3
agar, 1 mg x l(-1) kinetin, and three levels of 2,4-D. The highest callus relative growth was obtained on medium with 1.5 mg x l(-1) 2,4-D and 1 mg x l(-1) kinetin. Shoot primordia (SP) induction from > 18-months-old calluses was evaluated on several media; the highest percentage of SP induction (89
) and average number of SP per callus (8.6) were obtained with clone [quot ]265[quot ] on MS medium with 5 mg x l(-1) 2iP, 1 mg x l(-1) IAA, 3
sucrose and 0.9
agar. The highest percentage of root induction (100
) was achieved with clone 265 on MS medium with 0.1 mg x l(-1) kinetin, 0.1 mg x l(-1) NAA, 1.32 mg x l(-1) ancymidol, 7
glucose and 0.8
agar. Important medium x genotype interactions were detected, pointing to the need of adjusting this and other in vitro protocols for specific asparagus genotypes.
RESUMO
Callus growth and plant regeneration from long-term callus cultures were studied in two elite clones of Asparagus officinalis cv. Argenteuil, to establish a suitable protocol for a prospective in vitro selection program. Callus initiation and growth was evaluated on MS medium with 3% sucrose, 0.9% agar, 1 mg x l(-1) kinetin, and three levels of 2,4-D. The highest callus relative growth was obtained on medium with 1.5 mg x l(-1) 2,4-D and 1 mg x l(-1) kinetin. Shoot primordia (SP) induction from > 18-months-old calluses was evaluated on several media; the highest percentage of SP induction (89%) and average number of SP per callus (8.6) were obtained with clone "265" on MS medium with 5 mg x l(-1) 2iP, 1 mg x l(-1) IAA, 3% sucrose and 0.9% agar. The highest percentage of root induction (100%) was achieved with clone '265' on MS medium with 0.1 mg x l(-1) kinetin, 0.1 mg x l(-1) NAA, 1.32 mg x l(-1) ancymidol, 7% glucose and 0.8% agar. Important medium x genotype interactions were detected, pointing to the need of adjusting this and other in vitro protocols for specific asparagus genotypes.
Assuntos
Asparagus/crescimento & desenvolvimento , Asparagus/fisiologia , Regeneração , Ácido 2,4-Diclorofenoxiacético/farmacologia , Compostos de Benzil , Células Clonais , Meios de Cultura/química , Técnicas de Cultura/métodos , Citocininas/farmacologia , Ácidos Indolacéticos/farmacologia , Cinetina/farmacologia , Reguladores de Crescimento de Plantas/farmacologia , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/fisiologia , Purinas , Fatores de TempoRESUMO
Callus growth and plant regeneration from long-term callus cultures were studied in two elite clones of Asparagus officinalis cv. Argenteuil, to establish a suitable protocol for a prospective in vitro selection program. Callus initiation and growth was evaluated on MS medium with 3
sucrose, 0.9
agar, 1 mg x l(-1) kinetin, and three levels of 2,4-D. The highest callus relative growth was obtained on medium with 1.5 mg x l(-1) 2,4-D and 1 mg x l(-1) kinetin. Shoot primordia (SP) induction from > 18-months-old calluses was evaluated on several media; the highest percentage of SP induction (89
) and average number of SP per callus (8.6) were obtained with clone [quot ]265[quot ] on MS medium with 5 mg x l(-1) 2iP, 1 mg x l(-1) IAA, 3
sucrose and 0.9
agar. The highest percentage of root induction (100
) was achieved with clone 265 on MS medium with 0.1 mg x l(-1) kinetin, 0.1 mg x l(-1) NAA, 1.32 mg x l(-1) ancymidol, 7
glucose and 0.8
agar. Important medium x genotype interactions were detected, pointing to the need of adjusting this and other in vitro protocols for specific asparagus genotypes.
RESUMO
The cultivated potato, Solanum tuberosum L. (2n=4x=48), has a very large number of related wild and cultivated tuber-bearing species widely distributed in the Americas. These species, grouped in 16 taxonomic series, range from the diploid to the hexaploid level. Polyploid species are either disomic or polysomic, and sexual polyploidization via genetically controlled 2 n gametes has played a major role in their evolution. Species are separated in nature by geographical and ecological barriers. However, there are several examples of sympatric species that share the same niches but do not readily cross (i.e., the diploids S. commersonii and S. chacoense in certain areas of Argentina). External barriers alone are, therefore, not sufficient to explain species integrity. In addition, there is no strong evidence indicating that genome differentiation is important in the group. In this review we present evidence supporting the assertion that interspecific pollen-pistil incompatibility, nuclear-cytoplasmic male sterility, and the endosperm are major forces that strengthen the external hybridization barriers allowing, at the same time and under specific circumstances, a certain amount of gene exchange without jeopardizing the integrity of the species.
Assuntos
Flores/genética , Genoma de Planta , Pólen/genética , Solanum tuberosum/genética , Diploide , Infertilidade/genética , Reprodução , Solanum tuberosum/classificação , Solanum tuberosum/fisiologia , Especificidade da EspécieRESUMO
Callus induction, growth and embryogenic differentiation were studied in two selected genotypes of Asparagus officinalis L. cv. Argenteuil, to develop a protocol for somatic embryogenesis. Two experiments were carried out. In the first, four explant types (spear sections and lateral buds, both of in vivo and in vitro origin), and three levels of 2,4-D (1.5, 5 and 10 mg.l-1) and two of KIN (0 and 1 mg.l-1) added to MS basal medium, were tested during the three initial culture stages (90 d period). All factors were included in one factorial design to statistically analyze interaction effects. Interactions between genotype, explant type and time of culture initiation were significant for callus induction and growth during the two initial culture stages. The addition of kinetin enhanced callus induction and growth, and high levels of 2,4-D depressed callus growth. The average embryogenic differentiation was < 2% overall (11% with the best factor combination). In the second experiment, another explant type (bud clusters) was tested; the average embryogenic differentiation was 1.9% (best combination: 5.6%). For the two genotypes studied, the best factor combinations were the culture of in vivo lateral buds or bud clusters on MS basal medium with 1.5 mg.l-1 2,4-D and 1 mg.l-1 KIN.
Assuntos
Adenina/análogos & derivados , Adenina/farmacologia , Liliaceae/embriologia , Reguladores de Crescimento de Plantas/farmacologia , Ácido 2,4-Diclorofenoxiacético/farmacologia , Diferenciação Celular/efeitos dos fármacos , Genótipo , Herbicidas/farmacologia , Cinetina , Liliaceae/genética , Sementes/citologia , Sementes/embriologia , Sementes/genéticaRESUMO
Callus induction, growth and embryogenic differentiation were studied in two selected genotypes of Asparagus officinalis L. cv. Argenteuil, to develop a protocol for somatic embryogenesis. Two experiments were carried out. In the first, four explant types (spear sections and lateral buds, both of in vivo and in vitro origin), and three levels of 2,4-D (1.5, 5 and 10 mg.l-1) and two of KIN (0 and 1 mg.l-1) added to MS basal medium, were tested during the three initial culture stages (90 d period). All factors were included in one factorial design to statistically analyze interaction effects. Interactions between genotype, explant type and time of culture initiation were significant for callus induction and growth during the two initial culture stages. The addition of kinetin enhanced callus induction and growth, and high levels of 2,4-D depressed callus growth. The average embryogenic differentiation was < 2
overall (11
with the best factor combination). In the second experiment, another explant type (bud clusters) was tested; the average embryogenic differentiation was 1.9
(best combination: 5.6
). For the two genotypes studied, the best factor combinations were the culture of in vivo lateral buds or bud clusters on MS basal medium with 1.5 mg.l-1 2,4-D and 1 mg.l-1 KIN.
RESUMO
Garden asparagus, Asparagus officinalis, is reproductively isolated from a related ornamental species with potential breeding value, Asparagus densiflorus cv. Sprengeri, by pre- and post-zygotic barriers. The latter barrier operates at the endosperm level five days after pollination in A. officinalis x A. densiflorus crosses. To try to circumvent this barrier, in vitro embryo rescue using ovule and ovary cultures was tested. Controlled interspecific crosses were made and 2,032 ovules and 826 ovaries were cultured three days after pollination under various culture media and incubation conditions. Ovaries cultured for 60 days became red (similar to mature fruits), but seed formation was incomplete. Transfer of ovules to other media was necessary to promote embryo development. The interspecific embryos increased their length from 35 microns at the initiation of culture to 1,900 microns after 120 days of culture, but seedlings were not obtained. Histological studies revealed differentiation of protoderm only. The possible causes of the failure of the embryos to complete differentiation and morphogenesis are discussed.(AU)
Assuntos
RESEARCH SUPPORT, NON-U.S. GOVT , Adenina/análogos & derivados , Células Cultivadas/metabolismo , Quimera/crescimento & desenvolvimento , Germinação/fisiologia , Liliaceae/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento , Ácido 2,4-Diclorofenoxiacético/farmacologia , Adenina/farmacologia , Técnicas de Cultura de Células , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Células Cultivadas/citologia , Células Cultivadas/efeitos dos fármacos , Quimera/fisiologia , Meios de Cultura , Germinação/efeitos dos fármacos , Giberelinas/farmacologia , Liliaceae/efeitos dos fármacos , Liliaceae/metabolismo , Ácidos Naftalenoacéticos/farmacologia , Reguladores de Crescimento de Plantas/farmacologia , Plantas/citologia , Plantas/crescimento & desenvolvimento , Plantas/metabolismo , Sementes/efeitos dos fármacos , Sementes/metabolismo , Vitaminas/farmacologiaRESUMO
Garden asparagus, Asparagus officinalis, is reproductively isolated from a related ornamental species with potential breeding value, Asparagus densiflorus cv. Sprengeri, by pre- and post-zygotic barriers. The latter barrier operates at the endosperm level five days after pollination in A. officinalis x A. densiflorus crosses. To try to circumvent this barrier, in vitro embryo rescue using ovule and ovary cultures was tested. Controlled interspecific crosses were made and 2,032 ovules and 826 ovaries were cultured three days after pollination under various culture media and incubation conditions. Ovaries cultured for 60 days became red (similar to mature fruits), but seed formation was incomplete. Transfer of ovules to other media was necessary to promote embryo development. The interspecific embryos increased their length from 35 microns at the initiation of culture to 1,900 microns after 120 days of culture, but seedlings were not obtained. Histological studies revealed differentiation of protoderm only. The possible causes of the failure of the embryos to complete differentiation and morphogenesis are discussed.
Assuntos
Adenina , Células Cultivadas/metabolismo , Quimera , Germinação/fisiologia , Liliaceae , Sementes , /farmacologia , Ácidos Naftalenoacéticos/farmacologia , Adenina , Técnicas de Cultura de Células , Células Cultivadas/citologia , Células Cultivadas/efeitos dos fármacos , Quimera , Meios de Cultura , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Germinação/efeitos dos fármacos , Giberelinas , Liliaceae , Reguladores de Crescimento de Plantas , Plantas , Sementes , VitaminasRESUMO
Garden asparagus, Asparagus officinalis, is reproductively isolated from a related ornamental species with potential breeding value, Asparagus densiflorus cv. Sprengeri, by pre- and post-zygotic barriers. The latter barrier operates at the endosperm level five days after pollination in A. officinalis x A. densiflorus crosses. To try to circumvent this barrier, in vitro embryo rescue using ovule and ovary cultures was tested. Controlled interspecific crosses were made and 2,032 ovules and 826 ovaries were cultured three days after pollination under various culture media and incubation conditions. Ovaries cultured for 60 days became red (similar to mature fruits), but seed formation was incomplete. Transfer of ovules to other media was necessary to promote embryo development. The interspecific embryos increased their length from 35 microns at the initiation of culture to 1,900 microns after 120 days of culture, but seedlings were not obtained. Histological studies revealed differentiation of protoderm only. The possible causes of the failure of the embryos to complete differentiation and morphogenesis are discussed.
Assuntos
Adenina/análogos & derivados , Células Cultivadas/metabolismo , Quimera/crescimento & desenvolvimento , Germinação/fisiologia , Liliaceae/crescimento & desenvolvimento , Sementes/crescimento & desenvolvimento , Ácido 2,4-Diclorofenoxiacético/farmacologia , Adenina/farmacologia , Técnicas de Cultura de Células , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/fisiologia , Células Cultivadas/citologia , Células Cultivadas/efeitos dos fármacos , Quimera/fisiologia , Meios de Cultura , Germinação/efeitos dos fármacos , Giberelinas/farmacologia , Isopenteniladenosina , Liliaceae/efeitos dos fármacos , Liliaceae/metabolismo , Ácidos Naftalenoacéticos/farmacologia , Células Vegetais , Desenvolvimento Vegetal , Reguladores de Crescimento de Plantas/farmacologia , Plantas/metabolismo , Sementes/efeitos dos fármacos , Sementes/metabolismo , Vitaminas/farmacologiaRESUMO
Garden asparagus, Asparagus officinalis, is reproductively isolated from a related ornamental species with potential breeding value, Asparagus densiflorus cv. Sprengeri, by pre- and post-zygotic barriers. The latter barrier operates at the endosperm level five days after pollination in A. officinalis x A. densiflorus crosses. To try to circumvent this barrier, in vitro embryo rescue using ovule and ovary cultures was tested. Controlled interspecific crosses were made and 2,032 ovules and 826 ovaries were cultured three days after pollination under various culture media and incubation conditions. Ovaries cultured for 60 days became red (similar to mature fruits), but seed formation was incomplete. Transfer of ovules to other media was necessary to promote embryo development. The interspecific embryos increased their length from 35 microns at the initiation of culture to 1,900 microns after 120 days of culture, but seedlings were not obtained. Histological studies revealed differentiation of protoderm only. The possible causes of the failure of the embryos to complete differentiation and morphogenesis are discussed.
RESUMO
A group of wild, tuber-bearing species from Northwest Argentina, belonging to the series Tuberosa, Solarium spegazzini Bitt. (spg, 2n=2x=24), S. gourlayi Hawkes (grl, 2n=2x=24 and 2n=4x=48) and S. oplocense Hawkes (opl, 2n=6x=72), and Cuneolata, S. infundibuliforme Phil (ifd, 2n=2x=24), is being used to investigate the mode of origin of polyploids in the genus Solanum. 2n gametes have been detected in the diploid species ifd and spg and in a diploid race of grl, using cytological and breeding approaches. Twenty-two introductions of spg, 8 of grl and 26 of ifd have been tested for 2n pollen; 59%, 63% and 54% of them, respectively, had at least one 2n pollen producing plant. These introductions comprised 238, 76 and 235 plant respectively, of which 20, 16, and 32 plant produced 5% or more 2n pollen. The mechanism of 2n pollen formation was determined in several plant of 2x spg, 2x grl and 2x ifd. All of them were found to form diplandroids via parallel spindles. This mechanism, which gives meiotic products genetically equivalent to first division restitution gametes, is under control of the Mendelian recessive ps. The results suggest that the allele ps is widely distributed in natural populations of the three diploids, and that its frequency is very high. These species are seen as valuable material for population genetic studies, and for the eventual incorporation into a breeding scheme involving sexual polyploidization via 2n gametes.