Allotetraploid behavior of hybrids of Medicago sativa L. and M. papillosa Boiss.

Genome ◽  
1989 ◽  
Vol 32 (1) ◽  
pp. 6-11 ◽  
Author(s):  
T. J. McCoy ◽  
G. L. Quarisa
Keyword(s):  
Medicago Sativa ◽  
Pollen Mother Cell ◽  
Embryo Culture ◽  
Mother Cell ◽  
Cytogenetic Analysis ◽  
Interspecific Hybrids ◽  
Backcross Progeny ◽  
Male Sterile ◽  
Genomic Constitution ◽  
Medicago Sativa L

Diploid (2n = 2x = 16), triploid (2n = 3x = 24), and tetraploid (2n = 4x = 32) interspecific hybrids between alfalfa (Medicago sativa L.) and M. papillosa Boiss. were recovered either from seed (the triploid hybrids) or from ovule–embryo culture (the diploid and tetraploid hybrids). Cytogenetic analysis of diploid interspecific hybrids (with one genome of M. sativa, designated S, and one genome of M. papillosa, designated P), indicated significant genomic affinity, with an average of 7.6 bivalents and 0.8 univalents per pollen mother cell. In contrast, cytogenetic analysis of the triploid interspecific hybrids (with one S genome and two P genomes) indicated little if any genomic affinity between M. sativa and M. papillosa. In 7 of 14 triploid hybrids analyzed no trivalent configurations were observed, and in the other hybrids, trivalent frequency ranged from 0.1 to 0.4 per pollen mother cell. Tetraploid interspecific hybrids with two S and two P genomes had predominantly bivalent pairing. Based on the lack of homology of S and P genomes, the tetraploid hybrids are basically allotetraploids (SSPP). Therefore, backcross progeny from crossing the tetraploid hybrids with tetraploid M. sativa have the genomic constitution SSSP. Univalents and trivalents were observed in first backcross (BC1) progeny, as expected, based on an allotetraploid interpretation. Most of the BC1 progeny were partially or completely male sterile, and female fertility was significantly reduced. Potential uses of homoeologous genomes such as M. papillosa in alfalfa genetic and breeding studies are discussed.Key words: cytogenetics, interspecific hybrids, ovule –embryo culture.

Cytogenetic analysis of interspecific hybrids between alfalfa (Medicago sativa L.) and M. rhodopea Velen.

Genome ◽  
1987 ◽  
Vol 29 (6) ◽  
pp. 853-858 ◽  
Author(s):  
C. R. Denton ◽  
T. J. McCoy
Keyword(s):  
Medicago Sativa ◽  
Embryo Culture ◽  
Pollen Germination ◽  
Interspecific Hybrids ◽  
Backcross Progeny ◽  
Microspore Mother Cell ◽  
Triploid Hybrid ◽  
Pollen Stainability ◽  
Medicago Sativa L ◽  
High Level

Interspecific hybrids between diploid (2n = 2x = 16) Medicago sativa L. and diploid (2n = 2x = 16) M. rhodopea Velen., were recovered using an ovule–embryo culture methodology. Most hybrids were vigorous, and morphological comparisons demonstrated that F1 hybrids were generally intermediate between that of the parents. Peroxidase isozyme phenotypes of the F1 hybrids confirmed hybridity. The chromosome number of most of the hybrids was diploid (2n = 2x = 16), with the exceptions of two triploids (2n = 3x = 24) and two tetraploid (2n = 4x = 32) plants. Chromosome pairing configurations in diploids were almost exclusively eight bivalents or seven bivalents and two univalents, indicating a high level of homology between the M. sativa and M. rhodopea genomes. However, the one triploid hybrid analyzed had only 0.4 trivalents per microspore mother cell indicating preferential pairing of parental genomes. Pollen stainability, pollen germination, and fertility of the diploid F1 hybrid plants were very low; however, it was possible to obtain backcross progeny (BC1) from seed. Pollen stainability, pollen germination, and fertility of the BC1 plants were also very low; however, most BC1 plants had workable levels of male and female fertility. The utilization of M. rhodopea in studies of the evolution of hexaploid Medicago species is discussed. Key words: interspecific hybrids, ovule–embryo culture, isozymes, Medicago.

Uneven ploidy levels and a reproductive mutant required for interspecific hybridization of Medicago sativa L. × Medicago dzhawakhetica Bordz.

1984 ◽  
Vol 26 (5) ◽  
pp. 511-518 ◽  
Author(s):  
T. J. McCoy ◽  
L. Y. Smith
Keyword(s):  
Medicago Sativa ◽  
Interspecific Hybrids ◽  
Backcross Progeny ◽  
Male Sterile ◽  
Plant Variation ◽  
Ploidy Levels ◽  
Male And Female ◽  
Large Numbers ◽  
Medicago Sativa L ◽  
Efficient Recovery

Crossing diploid (2n = 2x = 16) Medicago sativa L. (homozygous for the gene, jp, that causes failure of the postmeiotic cytokinesis) and tetraploid (2n = 4x = 32) Medicago dzhawakhetica Bordz. resulted in efficient recovery of interspecific hybrids. Interspecific hybrids were produced in large numbers (1.15 – 5.60 hybrids per pollination), comparable to intraspecific same-ploidy level crosses within M. sativa. All 237 interspecific hybrids were triploid (2n = 3x = 24) or near triploid. Morphologically, the F1 hybrids were intermediate, although they tended to be more similar to the M. dzhawakhetica parent. Medicago dzhawakhetica was resistant to spring blackstem (caused by Phoma medicaginis Malb. and Roum.), whereas the M. sativa parents were susceptible. The F1 hybrids were also resistant to P. medicaginis. Chromosome pairing in the hybrids showed plant-to-plant variation; however, trivalent frequencies in some F1 hybrids were comparable to that observed in M. sativa triploids, indicating potential for recombination between M. sativa and M. dzhawakhetica genomes. Although the triploid hybrids were male sterile, and nearly female sterile, it was possible to produce backcross progeny. The first backcross was both male and female fertile.Key words: Medicago, hybridization, breeding, tetraploid, triploid, sterility.

Relationships between inbreeding, meiotic irregularity, and fertility in alfalfa

1986 ◽  
Vol 28 (1) ◽  
pp. 130-137 ◽  
Author(s):  
S. E. Smith ◽  
R. P. Murphy
Keyword(s):  
Medicago Sativa ◽  
Seed Production ◽  
Inbreeding Depression ◽  
Pollen Mother Cell ◽  
Mother Cell ◽  
Pollen Parent ◽  
Meiotic Behavior ◽  
Negatively Associated ◽  
Meiotic Irregularity ◽  
Medicago Sativa L

Fertility (seed production) in alfalfa (Medicago sativa L.) is severely depressed by inbreeding; however, little is known of the factors directly responsible for this depression. Irregularities in meiotic behavior could be partially responsible for the inbreeding depression in fertility observed. This study considered relationships between fertility, inbreeding, and irregularity in microsporogenesis. Fertility declined markedly with inbreeding in the materials examined (S0–S3). Irregularity in microsporogenesis, as measured by the percent irregular quartets, (i.e., quartets with micronuclei, supernumerary microspores, or irregular cytokinesis) increased significantly with inbreeding. Increases in quartet irregularity were associated with increases in the number of univalents per pollen mother cell observed at metaphase I. Considering all materials studied, the percentage of irregular quartets was negatively and significantly correlated with fertility as both a seed and a pollen parent. In more detailed analyses, it was observed that the percent irregular quartets was negatively associated with fertility as a pollen parent only when levels of irregularity were relatively high. No association was observed between the percent irregular quartets and fertility when levels of irregularity were relatively low.Key words: Medicago, microsporogenesis, seed production, breeding, fertility.

Interspecific hybridization of Medicago sativa L. and M. rupestris M. B. using ovule–embryo culture

1985 ◽  
Vol 27 (2) ◽  
pp. 238-245 ◽  
Author(s):  
T. J. McCoy
Keyword(s):  
Medicago Sativa ◽  
Embryo Culture ◽  
Interspecific Hybrid ◽  
Interspecific Hybrids ◽  
Embryo Rescue ◽  
Culture Method ◽  
Hybrid Plants ◽  
Successful Recovery ◽  
Hybrid Embryo ◽  
Medicago Sativa L

An ovule–embryo culture method was used to produce the first interspecific hybrids between alfalfa (Medicago sativa L.) and Medicago rupestris M. B. Culture of fertilized ovules from the cross diploid (2n = 2x = 16) M. sativa (jpjp) × diploid (2n = 2x = 16) M. rupestris began 14 days after pollination. After 5 days in culture, the interspecific hybrid embryo was removed and transferred to fresh medium, where development into a plant occurred. Forty-six M. sativa – M. rupestris F1 hybrids have been recovered using this technique. All but one of the 46 F1 hybrids were diploid (2n = 2x = 16); the only exception was tetraploid (2n = 4x = 32). The most frequent meiotic configurations observed in the F1 hybrid plants were eight bivalents or seven bivalents and two univalents, indicating significant homology between M. sativa and M. rupestris genomes. However, pollen stainability (0–12%) and pollen germination (0–6%) were extremely low. Similar to the production of the F1, no first backcross (BC1) plants were obtained from seed; however, the ovule–embryo culture method was found to be a very effective method for recovering BC1 plants and hundreds of BC1 plants have been produced. The BC1 plants from crossing the F1 with diploid M. sativa were predominantly diploid. Medicago rupestris can now be considered a potential germplasm source for alfalfa improvement. The ovule–embryo culture method represents the first successful recovery of Medicago interspecific hybrids via some form of embryo rescue. Importantly, it appears this technique can be applied to other interspecific hybrid combinations in the Medicago genus.Key words: Medicago, alfalfa, embryo culture, interspecific hybrid.

Interspecific hybrids between Medicago sativa L. and annual Medicago containing Alfafa weevil resistance

2005 ◽  
Vol 84 (1) ◽  
pp. 80-89 ◽  
Author(s):  
Yuko Mizukami ◽  
Mitsuru kato ◽  
Tadashi Takamizo ◽  
Michio Kanbe ◽  
Susumu Inami ◽  
...  
Keyword(s):  
Medicago Sativa ◽  
Interspecific Hybrids ◽  
Medicago Sativa L ◽  
Annual Medicago

A potential solution to the chromosome instability problem in hexaploid alfalfa, Medicago sativa L.

Genome ◽  
1989 ◽  
Vol 32 (2) ◽  
pp. 302-306 ◽  
Author(s):  
T. J. McCoy
Keyword(s):  
Medicago Sativa ◽  
Interspecific Hybrids ◽  
Chromosome Instability ◽  
Chromosome Stability ◽  
Potential Solution ◽  
Chromosome Counts ◽  
Instability Problem ◽  
Commercial Use ◽  
Medicago Sativa L ◽  
The Cross

Autohexaploid alfalfa (2n = 6x = 48) is chromosomally unstable, which prevents commercial use. The objective of this investigation was to test whether synthesizing Medicago hexaploids (2n = 6x = 48) that are alloautohexaploids results in chromosomally stable hexaploid populations. Previous research in our laboratory demonstrated a lack of affinity between the genomes of alfalfa and M. papillosa Boiss. Triploid (2n = 3x = 24) interspecific hybrids with two M. papillosa genomes and one genome of M. sativa were readily recovered from seed following the cross (2x) M. sativa × (4x) M. papillosa. For this study, the triploids were chromosomally doubled to produce alloautohexaploids, and these alloautohexaploids were used to test chromosome stability in hexaploids with no more than four homologous genomes. Chromosome counts of 47 progeny from intercrossing the alloautohexaploids demonstrated all were hexaploid, indicating chromosome stability. Designing novel genomic combinations based on genomic affinity may result in higher yielding alfalfa populations that have a modified cytogenetic structure.Key words: Medicago cancellata, Medicago papillosa, Medicago saxatilis, genomic affinity, hexaploids.

Potential of trispecies bridge crosses and random amplified polymorphic DNA markers for introgression of Medicago daghestanica and M. pironae germplasm into alfalfa (M. sativa)

Genome ◽  
1993 ◽  
Vol 36 (3) ◽  
pp. 594-601 ◽  
Author(s):  
T. J. McCoy ◽  
C. S. Echt
Keyword(s):  
Embryo Culture ◽  
Interspecific Hybrids ◽  
Rapd Markers ◽  
Random Amplified Polymorphic Dna ◽  
Embryo Rescue ◽  
Backcross Progeny ◽  
Culture Technique ◽  
Randomly Amplified Polymorphic Dna ◽  
Bivalent Chromosome ◽  
Diploid Level

This report describes the production and cytology of the first interspecific hybrids between cultivated alfalfa (Medicago sativa L.) at the diploid level (2n = 2x = 16) and the diploid (2n = 2x = 16) perennial species M. daghestanica and M. pironae. An ovule–embryo culture technique was required to rescue hybrid embryos and all hybrids were diploid. Predominately bivalent chromosome pairing was observed at meiotic metaphase. All F1 hybrids were male and female sterile and no species backcross progeny could be produced. We discovered that trispecies hybrids could be efficiently recovered via crossing diploid F1 interspecific hybrids of M. sativa × M. rupestris with either M. daghestanica or M. pironae. Ovule–embryo culture was also required to recover these trispecies hybrids with recovery efficiency of trispecies hybrids about 10 times greater than for bispecies hybrids. Most chromosomes paired as bivalents in the trispecies hybrids. Importantly, progeny can be recovered from crossing the trispecies hybrids with M. sativa. Therefore, the M. sativa × M. rupestris hybrids provide a bridge cross to potential introgression of M. daghestanica or M. pironae germplasm. Analysis of randomly amplified polymorphic DNA (RAPD) markers in the trispecies hybrids indicates that RAPD markers offer considerable potential for assaying germplasm introgression following complex hybridizations of the type reported here.Key words: randomly amplified polymorphic DNA, Medicago interspecific hybrids, embryo rescue.

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