Distribution and Characterization of Heterochromatic DNA in the Tetraploid African Population Alfalfa Genome

Bauchan, Gary R.; Hossain, M. A.

doi:10.2135/cropsci2001.1921

Cited by 11 publications

(18 citation statements)

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“…(the putative ancestor of cultivated alfalfa, which has similar C‐banding patterns to subsp. caerulea [Bauchan and Hossain, 2001]) and M. sativa subsp. falcata (Bauchan and Hossain, 1997).…”

Section: Resultsmentioning

confidence: 99%

Inbreeding Depression for Fertility and Biomass in Advanced Generations of Inter‐ and Intrasubspecific Hybrids of Tetraploid Alfalfa

Brummer

2009

Crop Science

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Hybrids between Medicago sativa subsp. sativa L. (hereafter “sativa”) and M. sativa subsp. falcata (L.) Arcang. (hereafter “falcata”) often express heterosis for yield. Yield generally declines when hybrids are inbred due to the loss of desirable dominant alleles or epistatic combinations. We hypothesized that inbreeding sativa–falcata hybrids may show more extensive yield loss than intrasubspecific crosses because of the large genetic difference between subspecies. Our objective was to compare fertility in the greenhouse and biomass production in the field of F1 hybrids and their F2 and S1 generations in both intra‐ and intersubspecific crosses. Field experiments including F1, F2, S1, and double‐cross populations were planted in two locations in Iowa in 2003 and evaluated for yield in 2 yr. Sativa × falcata crosses (SFC) showed greater F1 fertility than intrasubspecific crosses, suggesting that the two subspecies have similar chromosome structure. The SFC did not show high‐parent F1 heterosis, probably because of an intensive harvest schedule favoring sativa × sativa hybrids. However, SFC showed greater inbreeding depression in both F2 and S1 generations than intrasubspecific crosses, possibly reflecting a greater loss of favorable complementary gene interactions. These results suggest that selection within each parental population followed by intercrossing to produce population hybrids may be a better way to improve biomass with this germplasm than advancing hybrids into a recurrent selection program.

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Section: Resultsmentioning

confidence: 99%

Inbreeding Depression for Fertility and Biomass in Advanced Generations of Inter‐ and Intrasubspecific Hybrids of Tetraploid Alfalfa

Brummer

2009

Crop Science

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“…Several cytogenetic studies of somatic chromosomes of tetraploid alfalfa have been conducted (Agarwal and Gupta, 1983; Falistocco, 1987; Sclarbaum et al, 1988; Falistocco et al, 1995; Bauchan and Hossain, 2001a,b). Chromosome banding studies have shown that it is possible to identify individual chromosomes of M. sativa subspecies, including coerulea , falcata (Bauchan and Hossain, 1997, 1998a, 1999a), and sativa (Falistocco et al, 1995; Bauchan and Hossain, 2001a,b). Falistocco et al (1995) reported the first C‐banded karyotype of tetraploid alfalfa for the Italian cultivar Turrena.…”

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confidence: 99%

“…Falistocco et al (1995) reported the first C‐banded karyotype of tetraploid alfalfa for the Italian cultivar Turrena. Bauchan and Hossain (2001b) evaluated the C‐banding pattern of the African germplasm source of tetraploid alfalfa and concluded it resembled the C‐banding pattern of diploid M. sativa subsp. coerulea (Bauchan and Hossain, 1997).…”

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Chromosomal Polymorphism as Detected by C‐Banding Patterns in Chilean Alfalfa Germplasm ¹

2002

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A cytogenetic investigation was conducted on the tetraploid alfalfa [Medicago sativa subsp. sativa (L.) L. & L.] Chilean germplasm source PI 536534 using the combined techniques of C‐banding and image analysis. Cluster and multiple correspondence analyses were utilized to compare the C‐banding patterns of the Chilean germplasm source and the previously published African germplasm source. Cytogenetic analyses revealed polymorphisms for heterochromatic DNA in the 19 plants observed in detail. Abundant variability in the number, intensity, and location of constitutive heterochromatic DNA was noted; however, this variability was not sufficient to preclude recognition of homologous chromosomes. Five out of the 50 plants studied were aneuploids (2n = 4x + 1 = 33 or 2n = 4x − 1 = 31) because of the presence or absence of a chromosome with a satellite. The Chilean karyotype resembled the reference tetraploid African alfalfa karyotype; however, a reduction in the total amount of heterochromatic DNA was observed. Cluster analysis and multiple correspondence analysis based on all eight alfalfa genome chromosomes yielded no clear separation of Chilean and African germplasms. However, the analysis of C‐banding patterns of Homolog 1 of Chromosome 8 in Chilean and African germplasms was effective in separating the two germplasm sources with the exception of two individuals from each germplasm source which clustered together.

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“…Furthermore, autopolyploids often show different sets of homologous chromosomes, as has been reported in Medicago for tetraploid alfalfa (M. sativa subsp. sativa) by Bauchan and Hossain (2001). Complete bivalent pairing, and lack of multivalent formation (even at lower frequencies) was regularly observed in all species from the section Dendrotelis.…”

Section: Discussionmentioning

confidence: 81%

Karyological Observations in Medicago Section Dendrotelis (Fabaceae)

Rosato

Rosselló

2009

Folia Geobot

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Medicago section Dendrotelis comprises polyploid, woody shrubs restricted to rocky and cliff faces in coastal places of the Mediterranean basin, showing a very close morphology. This has resulted in controversial taxonomic studies, differing in the circumscription and number of recognized species (from one to three). In the present study, cytogenetic studies (meiotic analysis, C-banding, Ag-NOR banding) were made in M. arborea, M. strasseri, and M. citrina to determine their karyological and evolutionary relationships. The observation of meiocytes revealed a regular meiotic cycle in all species. At pachytene stage, chromosomes showed constitutive heterochromatic blocks (knobs) that were species-specific, and clearly discriminate M. arborea and M. strasseri from M. citrina. Conventional karyotypes of M. strasseri and M. arborea were similar concerning chromosome classes, the apparent chromosome length, and the morphology of the single NOR chromosome pair. However, C-banding technique revealed karyotypic differences between both species. In contrast, M. citrina exhibited a slightly asymmetric karyotype, the presence of two pairs of chromosomes showing secondary constrictions, a similar apparent chromosome length, and two pairs of active rDNA loci. Its C-banded karyotype strikingly differed from those observed in M. arborea and M. strasseri, and only three chromosome pairs showed heterochromatic blocks. These cytogenetic data indicate a clear evolutionary split in woody medics (tetraploid vs hexaploid species), reflecting divergent patterns of karyological evolution. Taken together, all karyological data unequivocally support the recognition of M. citrina as a distinct species.

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Distribution and Characterization of Heterochromatic DNA in the Tetraploid African Population Alfalfa Genome

Abstract: Barnes et al., 1977). One of these sources A reference karyotype of tetraploid alfalfa (Medicago sativa subsp.

Cited by 11 publications

References 14 publications

Inbreeding Depression for Fertility and Biomass in Advanced Generations of Inter‐ and Intrasubspecific Hybrids of Tetraploid Alfalfa

Inbreeding Depression for Fertility and Biomass in Advanced Generations of Inter‐ and Intrasubspecific Hybrids of Tetraploid Alfalfa

Chromosomal Polymorphism as Detected by C‐Banding Patterns in Chilean Alfalfa Germplasm ¹

Karyological Observations in Medicago Section Dendrotelis (Fabaceae)

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Distribution and Characterization of Heterochromatic DNA in the Tetraploid African Population Alfalfa Genome

Abstract: Barnes et al., 1977). One of these sources A reference karyotype of tetraploid alfalfa (Medicago sativa subsp.

Cited by 11 publications

References 14 publications

Inbreeding Depression for Fertility and Biomass in Advanced Generations of Inter‐ and Intrasubspecific Hybrids of Tetraploid Alfalfa

Inbreeding Depression for Fertility and Biomass in Advanced Generations of Inter‐ and Intrasubspecific Hybrids of Tetraploid Alfalfa

Chromosomal Polymorphism as Detected by C‐Banding Patterns in Chilean Alfalfa Germplasm 1

Karyological Observations in Medicago Section Dendrotelis (Fabaceae)

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Chromosomal Polymorphism as Detected by C‐Banding Patterns in Chilean Alfalfa Germplasm ¹