Cytological mechanisms of 2n egg formation in a diploid genotype of Medicago sativa subsp. falcata

Gametes formed without meiosis in alfalfa would be useful in basic and applied research. Therefore, the cytological analysis of macrosporogenesis of a diploid plant of Medicago sativa subsp. falcata (L.) Arcangeli (named PG-F9), previously selected as a good 2n egg producer, was conducted. A stain-c...

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Bibliographic Details
Published in:Euphytica 1994, Vol.75 (1-2), p.1-8
Main Author: Tavoletti, S. (Studi di Ancona Univ. (Italy). Dipartimento di Biotecnologie Agrarie ed Ambientali)
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Biological and medical sciences
CITOLOGIA
Cytogenetics
CYTOLOGIE
CYTOLOGY
DIPLOIDIA
DIPLOIDIE
DIPLOIDY
Fundamental and applied biological sciences. Psychology
GAMETE
GAMETES
GAMETOS
Generalities. Genetics. Plant material
Genetics and breeding of economic plants
GENOTIPOS
GENOTYPE
GENOTYPES
MEDICAGO SATIVA
MEIOSE
MEIOSIS
POLIPLOIDIA
POLYPLOIDIE
POLYPLOIDY
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Summary:Gametes formed without meiosis in alfalfa would be useful in basic and applied research. Therefore, the cytological analysis of macrosporogenesis of a diploid plant of Medicago sativa subsp. falcata (L.) Arcangeli (named PG-F9), previously selected as a good 2n egg producer, was conducted. A stain-clearing technique was applied which also allowed the analysis of microsporogenesis to be performed. Two mechanisms of 2n egg formation were determined: absence of the second meiotic division (mechanism of the SDR type) and apomeiosis. In particular, it is noteworthy that 2n eggs produced via apomeiosis should retain the same parental genotype, because apomeiotic cells give rise directly to the female gametophyte without undergoing meiosis. The presence of binucleate female gametophytes in the ovules at an early stage of development confirmed the presence of apomeiosis in PG-F9. These abnormalities concerned only macrosporogenesis; in fact, the analysis of microsporogenesis showed the production of normal tetrads of microspores after normal meiosis. Possible application of the discovered mechanisms of 2n egg production in breeding research are discussed.
ISSN:0014-2336
1573-5060
DOI:10.1007/BF00024525