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  • 1
    ISSN: 1432-203X
    Keywords: Key wordsTriticum aestivum ; Anther culture ; Colchicine ; Chromosome-doubling ; Doubled haploids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this study was to optimize the in vitro chromosome-doubling procedure in wheat anther culture. Colchicine, at concentrations of 100–5000 mg/l, was added to the induction medium for 1–5 days. Beneficial effects were obtained with concentrations of 100 and 1000 mg/l colchicine. With time, significant reductions in embryo–like structures as well as higher doubling indices were found. Similar results were obtained with the high- and low-responding genotypes. Colchicine (100 mg/l), added 5 and 20 days after inoculation for 1 and 3 days increased the induction response, but this value was reduced when colchicine was added 10 or 15 days after inoculation. The doubling effect was similar to the control, except for a significant increase with the 3-day application 20 days after inoculation. The highest success index was reached when colchicine was added to the culture medium after 20 days.
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  • 2
    ISSN: 1432-2242
    Keywords: Maize anther culture ; Chromosome doubling ; Cold treatment ; Colchicine ; Flow cytometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Efficient methods of chromosome doubling are critical for the production of microspore-derived, doubled-haploid (=DH) plants, especially if, as in maize anther culture, spontaneous chromosome doubling occurs infrequently. In the present study, colchicine (5–1000 mg/l) was added to the induction medium and maize anthers were incubated in the colchicine-containing medium for different durations (1–7 days). In order to improve overall anther culture response, the culture temperature was adjusted to 14°C during the first 7 days. Colchicine applied at low concentration, i.e. 5 mg/l (7 days), or for short duration, i.e. 1–3 days (250 mg/l), showed beneficial effects on the formation of embryolike structures (=ES) and thus led to increased plant production, but was comparatively ineffective regarding chromosome doubling. Optimal doubling effects were observed when anthers had been exposed to culture medium containing 250 and 1000 mg/l of colchicine (7 days); in these treatments the doubling index (=DI), defined as the quotient of the number of DH plants and the number of totally regenerated plants in a specific treatment, rose to 0.56 and 0.53, respectively, compared to 0.20 in the untreated control. However, colchicine administered at concentrations higher than 250 mg/l seemed to be detrimental to general plant production; thus, in spite of a high DI, the overall DH plant production was even lower than in the control treatment. Maximum DH plant production for three different genotypes was accomplished with culture medium containing 250 mg/l of colchicine (7 days). With the best-responding genotype (ETH-M 36) a DH plant production of 9.9 DH plants/100 anthers was accomplished, i.e. a 7-fold increase compared to the non-treated anthers. This is the first report on efficient chromosome doubling in anther culture by subjecting anthers to colchicinecontaining induction medium during a post-plating cold treatment. Chromosome doubling as described here becomes an integral part of the maize anther culture protocol and thus represents a rapid and economical way to produce DH plants.
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  • 3
    ISSN: 1432-203X
    Keywords: Maize ; Anther culture ; Autoclaving ; Medium toxicity ; Activated charcoal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Medium sterilization techniques (autoclaving, filter sterilization and separate sterilization of medium components), combined with preculture exposure to activated charcoal (AC) were evaluated for effects on maize anther culture response. The addition of AC to filter sterilized medium had no effect on the number of embryo-like-structures (ES) produced. For autoclaved medium, pre-culture AC treatment resulted in a 3-fold increase in ES yield over medium lacking AC. When AC was included, autoclaved medium was more productive than filter sterilized medium. Autoclaved media without AC gave lower response than filter sterilized medium. Separate sterilization of sucrose or FeEDTA was beneficial for media autoclaved in the absence of AC. However, when all components were autoclaved together in the presence of AC, there was no advantage to separate sterilization. The maximum ES frequency (224.6 ES/100 anthers) was obtained with the genotype ETH-M 52 cultured in autoclaved medium which had been exposed to AC (5 g/L) for 96 h prior to culture initiation. It is supposed that the higher ES frequencies observed with AC-treated, autoclaved media were due to the availability of glucose and fructose following heat-induced hydrolysis of sucrose and the AC-mediated adsorption of inhibitory compounds produced during autoclaving.
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  • 4
    ISSN: 1432-203X
    Keywords: Key words Zea mays L. ; Isolated microspores ; Androgenesis ; Plant regeneration ; Maltose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Pure fractions of maize (Zea mays L.) microspores at various densities were exposed to defined media containing different concentrations of maltose and sucrose. In general, lower carbohydrate concentrations (60, 90 g/l) yielded higher frequencies of embryo-like structures than a high concentration (120 g/l). Optimum cell density seemed to depend on the genotype, but densities above 80,000 microspores/ml led to reduced embryogenesis in all genotypes tested. Direct comparison of maltose and sucrose as carbohydrate source in the induction medium clearly demonstrated the superiority of maltose with regard to the regeneration frequency. For two out of three genotypes tested, maltose also enhanced the formation of embryo-like structures. The time of embryo transfer to callus induction media had a significant effect on regeneration frequency.
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  • 5
    ISSN: 1432-2242
    Keywords: Key words Maize anther culture ; Chromosome doubling ; Cold treatment ; Colchicine ; Flow cytometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Efficient methods of chromosome doubling are critical for the production of microspore-derived, doubled-haploid ( = DH) plants, especially if, as in maize anther culture, spontaneous chromosome doubling occurs infrequently. In the present study, colchicine (5–1000 mg/l) was added to the induction medium and maize anthers were incubated in the colchicine-containing medium for different durations (1–7 days). In order to improve overall anther culture response, the culture temperature was adjusted to 14 ·C during the first 7 days. Colchicine applied at low concentration, i.e. 5 mg/l (7 days), or for short duration, i.e. 1–3 days (250 mg/l), showed beneficial effects on the formation of embryo-like structures ( = ES) and thus led to increased plant production, but was comparatively ineffective regarding chromosome doubling. Optimal doubling effects were observed when anthers had been exposed to culture medium containing 250 and 1000 mg/l of colchicine (7 days); in these treatments the doubling index ( = DI), defined as the quotient of the number of DH plants and the number of totally regenerated plants in a specific treatment, rose to 0.56 and 0.53, respectively, compared to 0.20 in the untreated control. However, colchicine administered at concentrations higher than 250 mg/l seemed to be detrimental to general plant production; thus, in spite of a high DI, the overall DH plant production was even lower than in the control treatment. Maximum DH plant production for three different genotypes was accomplished with culture medium containing 250 mg/l of colchicine (7 days). With the best-responding genotype (ETH-M 36) a DH plant production of 9.9 DH plants/100 anthers was accomplished, i.e. a 7-fold increase compared to the non-treated anthers. This is the first report on efficient chromosome doubling in anther culture by subjecting anthers to colchicine-containing induction medium during a post-plating cold treatment. Chromosome doubling as described here becomes an integral part of the maize anther culture protocol and thus represents a rapid and economical way to produce DH plants.
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  • 6
    ISSN: 1432-2242
    Keywords: Key words In vitro selection ; Septoria nodorum ; Triticum aestivum L. ; Crude extract ; Toxin resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This study was carried out to develop an in vitro test for the identification of genotypes resistant to Septoria nodorum blotch. The basis for this project was a previous study in which a crude extract of S. nodorum was used as a selective agent (Keller et al. 1994). It was possible to distinguish resistant and susceptible cultivars in an in vitro test with zygotic embryos. In our project we wanted to test whether this in vitro test can also be used to detect resistant and susceptible genotypes in early segregating populations. Specific crosses between eight winter wheat lines showing contrasting resistance reaction for S. nodorum blotch on leaves and ears were made. The resistance level of both leaf and ear was evaluated after artificial inoculation in the field for the parental lines, the F1 progenies, as well as for segregating F3 and F4 populations. In addition, this plant material was tested in vitro using methods similar to those described by Keller et al. (1994), i.e. culturing immature zygotic embryos and mature seeds on selective media. A good agreement between in vitro screening and field resistance on the ear was found for the parental lines, the F1 and F4 generation but not for the F3 generations. This leads to the conclusion that the in vitro screening might be integrated into wheat breeding programs. Populations showing a high susceptibility to the pathogen metabolites in vitro could be discarded. Another promising implementation for wheat breeding would be the screening of advanced breeding material or candidate partners in a crossing program for resistance on the ear. However, the in vitro screening is not precise enough to select single plants in early segregating populations.
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  • 7
    ISSN: 1432-2242
    Keywords: Key words Septoria nodorum ; Triticum aestivum L. ; Inheritance ; Resistance breeding ; Artifical inoculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Sixteen crosses between eight winter wheat cultivars were screened for resistance to Septoria nodorum leaf and glume blotch in the F1 and F4 generations using artificial inoculation in the field. The F1 of most crosses showed dominance for susceptibility on both ear and leaf. The effects of general combining ability were of similar magnitude as the effects for specific combining ability. On the basis of the phenotypic difference of the parents, no prediction was possible about the amount and the direction of genetic variance in the segregating populations. The variation observed in this study both within and among the segregating populations suggests a quantitative inheritance pattern influencing the expression of the two traits. The components of variance between F2 families within a population were as high as (for S. nodorum blotch on the ear) or higher (for S. nodorum blotch on the leaf) than those between populations. Therefore, strong selection within a few populations may be as effective to obtain new resistant genotypes as selection in a large number of populations. In almost all crosses, progenies were found that were more resistant than the better parent. Thus transgression breeding may be a tool to breed for higher levels of resistance to S. nodorum blotch. Highly resistant genotypes were found even in combination with two susceptible parents. The genetic source for Septoria resistance is probably broader than is generally assumed and could be used to improve S. nodorum resistance by combination breeding followed by strong selection in large populations.
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  • 8
    ISSN: 1432-2242
    Keywords: Key words Erysiphe graminis ; Powdery mildew resistance ; QTL ; Triticum aestivum ; Triticum spelta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Powdery mildew is one of the major diseases of wheat in regions with a maritime or semi-continental climate and can strongly affect grain yield. The attempt to control powdery mildew with major resistance genes (Pm genes) has not provided a durable resistance. Breeding for quantitative resistance to powdery mildew is more promising, but is difficult to select on a phenotypic basis. In this study, we mapped and characterised quantitative trait loci (QTLs) for adult-plant powdery mildew resistance in a segregating population of 226 recombinant inbred lines derived from the cross of the Swiss wheat variety Forno with the Swiss spelt variety Oberkulmer. Forno possibly contains the Pm5 gene and showed good adult-plant resistance in the field. Oberkulmer does not have any known Pm gene and showed a moderate susceptible reaction. Powdery mildew resistance was assessed in field trials at two locations in 1995 and at three locations in 1996. The high heritability (h2=0.97) for powdery mildew resistance suggests that the environmental influence did not affect the resistance phenotype to a great extent. QTL analysis was based on a genetic map containing 182 loci with 23 linkage groups (2469 cM). With the method of composite interval mapping 18 QTLs for powdery mildew resistance were detected, explaining 77% of the phenotypic variance in a simultaneous fit. Two QTLs with major effects were consistent over all five environments. One of them corresponds to the Pm5 locus derived from Forno on chromosome 7B. The other QTL on 5A, was derived from the spelt variety Oberkulmer and did not correspond to any known Pm gene. In addition, five QTLs were consistent over three environments, and six QTLs over two environments. The QTL at the Pm5 locus showed a large effect, although virulent races for Pm5 were present in the mixture of isolates. Molecular markers linked with QTLs for adult-plant resistance offer the possibility of simultaneous marker-assisted selection for major and minor genes.
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  • 9
    ISSN: 1432-2242
    Keywords: Key words Lodging ; Morphological traits ; QTL ; Triticum aestivum ; Triticum spelta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Lodging can strongly affect both the grain yield and the quality of wheat. Lodging represents a quantitative trait and is difficult to assess on a phenotypic basis. Marker-assisted selection (MAS) could therefore become an important tool in breeding for lodging resistance. In this study, we mapped and characterised quantitative trait loci (QTLs) for lodging resistance, as well as morphological traits correlated with lodging, in a segregating population of 226 recombinant inbred lines derived from the cross of the lodging-resistant wheat variety Forno with the susceptible spelt variety Oberkulmer. Lodging, plant height, leaf width, leaf-growth habit, culm stiffness, culm swinging, culm thickness, days to ear emergence and days to flowering were assessed in field trials at two locations in 1996 and at one location in 1997. Additionally, at one location weight and length parameters were also assessed. Plant height and culm stiffness explained 77% of the phenotypic variance of lodging in a multiple regression model over all three environments. QTL analysis of lodging and morphological parameters was based on a genetic map containing 230 loci with 23 linkage groups (2469 cM). With the method of composite interval mapping nine QTLs for lodging resistance were detected, explaining 63% of the phenotypic variance in a simultaneous fit. Seven of these QTLs coincided with QTLs for morphological traits, reflecting the correlations between these traits and lodging. In our population the most efficient way to improve lodging resistance would be by a combination of indirect selection on plant height and culm stiffness together with MAS on the two QTLs for lodging resistance which did not coincide with QTLs for morphological traits.
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  • 10
    ISSN: 1432-203X
    Keywords: Anther culture ; Zea mays L. ; Temperature Treatment ; Proline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Comparison of different post-plating temperature regimes with a control treatment (27° C) revealed that a short-term cold (8/14°C:2/2 days or 14°C:4 days) as well as a heat treatment (30°C:14 days) increased the production of embryro-like-structures (ELS) from cultured maize anthers. The beneficial effects of short-term cold treatments were magnified 2–3 times when L-proline (PROL) was added to the induction medium (125–500 mg/L). In the best treatment (14°C:4 days, 125 mg/L L-proline) one genotype produced 143.5 ELS/100 anthers. Anthers subjected to high temperature (30°C:4 days, 30°C:7 days, 30°C:14 days) generally showed a lower response than did cold treated anthers, although genotypic differences were observed. Regeneration frequency did not appear to be affected by the presence of L-proline in the induction medium.
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