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  • 1
    Electronic Resource
    Electronic Resource
    Reproductive Behavior of Hexaploid/Diploid Wheat Hybrids (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 107 (1991), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The bottleneck restricting introgression of useful genes directly from diploid into hexaploid wheats is the low number of BC1F1 seeds obtained. In crosses between hexaploid wheat (Triticum aestivum L.; AABBDD) and Aegilops squarrosa L. (DD) or T. urartu Thum. (AA), this bottleneck may be overcome simply by pollinating a sufficient number of F1 spikes. However, hybrids between hexaploid wheat cultivars (T. aestivum) and T. monococcum L. (AA) generally are highly female-sterile, often having no pistils. One T. monococcum accession, PI 355520, when crossed with T. aestivum, produced hybrids with female fertility in the same range as that of T. aestivum/A. squarrosa or T. aestivum/T. urartu hybrids, ca. 0.5 to 1.0 backcross seed per spike. We found that female fertility was controlled by two duplicate genes in PI 355520, and that this accession can be used as a bridging parent to introgress genes from other T. monococcum accessions into hexaploid wheat. Pairing of homologous chromosomes was less frequent and weaker in such crosses than in T. aestivum/A. squarrosa crosses, but homoeologous bivalents occurred at a rate of almost 0.5 II per cell. Restitution division was detected in crosses involving all three diploid species and was confirmed cytologically in crosses with PI 355520. Chromosome numbers of BC1F1 plants ranged from 35 to 67; plants with 49 or more chromosomes occurred at frequencies of 0.09 to 0.21 among progeny of A. squarrosa and T. urartu and 0.29 in progeny of T. aestivum/T. monococcum crosses involving PI 355520. These results are consistent with those of previous studies, demonstrating the potential of direct Hexaploid/diploid crosses for rapidly introgressing useful genes into Hexaploid wheat with minimum disturbance of the background genotype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.1991.tb00537.x
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  • 2
    Electronic Resource
    Electronic Resource
    Agronomic Performance of Hexaploid Wheat Lines Derived from Direct Crosses between Wheat and Aegilops squarrosa1) (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 105 (1990), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Direct introgression of genes from diploid Aegilops squarrosa L into hexaploid wheat (Tnticum aestivumL.) is an efficient way of developing stable, hexaploid lines with unique, useful genes. 39 such lines derived front direct crosses to determine the effects of Ac. squarrosa germplasm were field-tested on productivity. Whereas some lines were agronomically inferior to the recurrent parent, others periormed at an equall or better level. In addition to the larget traits (Hessian-fly and leaf-rust resistance), other traits, including soilborne-mosaic-virus resistance and protein concentration, were improved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.1990.tb01285.x
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  • 3
    Electronic Resource
    Electronic Resource
    Genetic variation for grain yield and related traits in sorghum introgression populations (1984)
    Springer
    Theoretical and applied genetics 68 (1984), S. 145-153 
    Details
    ISSN: 1432-2242
    Keywords: Backcross ; Exotic germplasm ; Wild germplasm ; Epistasis ; Genetic regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Each of two sorghum (Sorghum bicolor (L.) Moench) cultivars were crossed with representatives of three wild sorghum races. Backcross-derived sorghum populations containing 3.125 to 50% wild germplasm were evaluated for grain yield, 100-kernel weight, days to flower, and plant height. Population means increased linearly with backcrossing for kernel weight, increased curvilinearly for grain yield, decreased curvilinearly for plant height, and changed erratically for days to flower. For all traits, the relationship between genetic variance and level of backcrossing deviated significantly from that expected based on an additive model. Genetic variance usually reached a maximum in the BC1 or BC2. The BC1 genetic variance for grain yield, averaged over matings, was twice as large as the average BC0 genetic variance. An epistatic model involving gene regulation is proposed as a plausible explanation for the results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252331
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  • 4
    Electronic Resource
    Electronic Resource
    Chromosome substitutions of Triticum timopheevii in common wheat and some observations on the evolution of polyploid wheat species (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 1291-1298 
    Details
    ISSN: 1432-2242
    Keywords: Triticum timopheevii ; Triticum aestivum ; Chromosome substitution ; C-banding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Whether the two tetraploid wheat species, the well known Triticum turgidum L. (macaroni wheat, AABB genomes) and the obscure T. timopheevii Zhuk. (AtAtGG), have monophyletic or diphyletic origin from the same or different diploid species presents an interesting evolutionary problem. Moreover, T. timopheevii and its wild form T. araraticum are an important genetic resource for macaroni and bread-wheat improvement. To study these objectives, the substitution and genetic compensation abilities of individual T. timopheevii chromosomes for missing chromosomes of T. aestivum ‘Chinese Spring’ (AABBDD) were analyzed. ‘Chinese Spring’ aneuploids (nullisomic-tetrasomics) were crossed with a T. timopheevii x Aegilops tauschii amphiploid to isolate T. timopheevii chromosomes in a monosomic condition. The F1 hybrids were backcrossed one to four times to Chinese Spring aneuploids without selection for the T. timopheevii chromosome of interest. While spontaneous substitutions involving all At- and G-genome chromosomes were identified, the targeted T. timopheevii chromosome was not always recovered. Lines with spontaneous substitutions from T. timopheevii were chosen for further backcrossing. Six T. timopheevii chromosome substitutions were isolated: 6At (6A), 2G (2B), 3G (3B), 4G (4B), 5G (5B) and 6G (6B). The substitution lines had normal morphology and fertility. The 6At of T. timopheevii was involved in a translocation with chromosome 1G, resulting in the transfer of the group-1 gliadin locus to 6At. Chromosome 2G substituted for 2B at a frequency higher than expected and may carry putative homoeoalleles of gametocidal genes present on group-2 chromosomes of several alien species. Our data indicate a common origin for tetraploid wheat species, but from separate hybridization events because of the presence of a different spectrum of intergenomic translocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223462
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  • 5
    Electronic Resource
    Electronic Resource
    Chromosome substitutions of Triticum timopheevii in common wheat and some observations on the evolution of polyploid wheat species (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 1291-1298 
    Details
    ISSN: 1432-2242
    Keywords: Key wordsTriticum timopheevii  ;  Triticum aestivum  ;   Chromosome substitution  ;  C-banding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Whether the two tetraploid wheat species, the well known Triticum turgidum L. (macaroni wheat, AABB genomes) and the obscure T. timopheevii Zhuk. have monophyletic or diphyletic origin from the same or different diploid species presents an interesting evolutionary problem. Moreover, T. timopheevii and its wild form T. araraticum are an important genetic resource for macaroni and bread-wheat improvement. To study these objectives, the substitution and genetic compensation abilities of individual T. timopheevii chromosomes for missing chromosomes of T. aestivum‘Chinese Spring’ (AABBDD) were analyzed. ‘Chinese Spring’ aneuploids (nullisomic-tetrasomics) were crossed with a T. timopheevii×Aegilops tauschii amphiploid to isolate T. timopheevii chromosomes in a monosomic condition. The hybrids were backcrossed one to four times to Chinese Spring aneuploids without selection for the T. timopheevii chromosome of interest. While spontaneous substitutions involving all and G-genome chromosomes were identified, the targeted T. timopheevii chromosome was not always recovered. Lines with spontaneous substitutions from T. timopheevii were chosen for further backcrossing. Six T. timopheevii chromosome substitutions were isolated: (6A), 2G (2B), 3G (3B), 4G (4B), 5G (5B) and 6G (6B). The substitution lines had normal morphology and fertility. The of T. timopheevii was involved in a translocation with chromosome 1G, resulting in the transfer of the group-1 gliadin locus to Chromosome 2G substituted for 2B at a frequency higher than expected and may carry putative homoeoalleles of gametocidal genes present on group-2 chromosomes of several alien species. Our data indicate a common origin for tetraploid wheat species, but from separate hybridization events because of the presence of a different spectrum of intergenomic translocations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050368
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  • 6
    Electronic Resource
    Electronic Resource
    Adjustment of parental frequencies to maximize the diversity of a synthetic population (1988)
    Springer
    Theoretical and applied genetics 75 (1988), S. 617-620 
    Details
    ISSN: 1432-2242
    Keywords: Genetic distance ; Random-mating ; Heterosis ; Multiline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A method is outlined for maximizing the mean genetic distance among plants in a synthetic population by adjusting the relative contributions of the population's parents. The largest latent vector of the genetic distance matrix is used to find relative parental frequencies. The largest increases in the diversity of a synthetic will be achieved when there are different-sized clusters of parents, with considerably larger distances between than within clusters. The method may have application in maximizing the yields of synthetic cultivars or the resistance of multi-line cultivars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00289129
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of parental divergence on F2 heterosis in winter wheat crosses (1990)
    Springer
    Theoretical and applied genetics 79 (1990), S. 241-250 
    Details
    ISSN: 1432-2242
    Keywords: Triticum aestivum L. ; Genetic diversity ; Coefficient of kinship ; Genetic distance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In winter wheat (Triticum aestivum L.), the development of a methodology to estimate genetic divergence between parental lines, when combined with knowledge of parental performance, could be beneficial in the prediction of bulk progeny performance. The objective of this study was to relate F2 heterosis for grain yield and its components in 116 crosses to two independent estimates of genetic divergence among 28 parental genotypes of diverse origins. Genetic divergence between parents was estimated from (a) pedigree relationships (coefficients of kinship) determined without experimentation, and (b) quantitative traits measured in two years of field experimentation in Kansas and North Carolina, USA. These distances, designated (1 -r) and G, respectively, provided ample differentiation among the parents. The 116 F2 bulks were evaluated at four locations in Kansas and North Carolina in one year. Significant rank correlations of 0.46 (P = 0.01) and 0.44 (P = 0.01) were observed between G and grain yield and kernel number heterosis, respectively. Although (1 -r) was poorly associated with grain yield heterosis, G and midparent performance combined to account for 50% of the variation in F2 yields among crosses when (1 -r) was above the median value, whereas they accounted for only 9% of the variation among crosses when (1-r) was below the median. Midparent and (1 -r) had equal effects on F2 grain yield (R 2= 0.40) when G was greater than the median value. A breeding strategy is proposed whereby parents are first selected on the basis of performance per se and, subsequently, crosses are made between genetically divergent parents that have both large quantitative (G) and pedigree divergence (1 -r).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225958
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  • 8
    Electronic Resource
    Electronic Resource
    Use of winter wheat x Triticum tauschii backcross populations for germplasm evaluation (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 571-577 
    Details
    ISSN: 1432-2242
    Keywords: Triticum tauschii ; Aegilops squarrosa Wheat ; Yield ; Protein ; Hardness ; Leaf rust
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The wild diploid goatgrass, Triticum tauschii (Coss.) Schmal., is an important source of genes for resistance to both diseases and insects in common wheat (Triticum aestivum L.) We have evaluated grain yield, kernel weight, protein concentration, and kernel hardness of 641 BC2 F1-derived families from direct crosses involving four T. aestivum cultivars and 13 T. tauschii accessions over 2 years and at two Kansas, USA, locations. On average, T. tauschii germplasm depressed grain yield and increased protein concentration, whereas kernel weight was affected either positively or negatively, depending on the T. tauschii parent. Three T. tauschii parents produced a large proportion of families with very soft endosperm. Some variation among progeny of different T. tauschii parents resulted from the segregation of genes for resistance to leaf rust (caused by Puccinia recondita Rob. ex Desm.). This study confirmed that random BC2-derived families can be used to evaluate the effects of T. tauschii genes in the field. This methodology, although laborious, can provide useful information which is not obtainable by the screening of T. tauschii accessions themselves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222005
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  • 9
    Electronic Resource
    Electronic Resource
    Expectations of means and genetic variances in backcross populations (1984)
    Springer
    Theoretical and applied genetics 68 (1984), S. 35-41 
    Details
    ISSN: 1432-2242
    Keywords: Introgression ; Population size ; Sampling ; Backcrossing ; Linkage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genetic variance among F2-derived lines of backcrosses (BCgF2-derived lines) depends on the backcross generation (g), the number of F1 plants crossed and selfed in generations 1 through g, and the number of BCgF2-derived lines evaluated. Additive genetic variance decreases linearly with backcrossing when one BCF1 plant per generation is crossed and selfed. The relationship is curvilinear if more than one BCF1 plant is used; as the number of BCF1 plants increases, additive genetic variance among BC1F2-derived lines approaches that among BC0F2-derived lines. The effect of population size on genetic variance is due both to fixation of alleles in previous generations and to sampling of genotypes in the population being evaluated. Dominance and repulsion linkage can cause small increases in genetic variance from BC0 to BC1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252308
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  • 10
    Electronic Resource
    Electronic Resource
    Genetic variance and drift in selfed and intermated populations derived from backcrossing (1984)
    Springer
    Theoretical and applied genetics 68 (1984), S. 183-186 
    Details
    ISSN: 1432-2242
    Keywords: Genetic variance ; Genetic drift ; Backcrossings ; Population size ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The genetic variance among random-mated lines derived from backcrossing (BCgS1 lines) depends upon the backcross generation (g) and the number (n) of BCgF1 plants crossed in generations 1 through g. There is little effect of n on genetic variance for n 〉 6. The genetic variance among BCgF2-derived lines is greater than that among BCgS1 lines for all g. If either BCgF2-derived or BCgS1 lines are used as a base population for recurrent selection, 8, 16, 32, and 64 BC1F1, BC2F1, BC3F1, and BC4F1 plants, respectively, should be used to avoid loss of donor alleles to drift.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00252336
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