Meiosis in polyhaploid Hordeum: hemizygous ineffective control of diploid-like behaviour in a hexaploid?

Mitotic and meiotic chromosome behaviour in new hybrids of Hordeum with Triticum and Secale

“…Such low frequencies either indicate great intergenomic differences within these hexaploid species and between them and H. vulgare or suggest suppression of homoeologous pairing. Evidence from H. vulgare hybrids with H. parodii (Subrahmanyam, 1978), H. lechieri (Rajhathy and Symko, 1974) and other species (Rajhathy et al, 1964) suggests that the H. vulgare genome may depress homoeologous chiasma formation when homoeologous genomes are in hybrids instead of haploids. Both hypoploid and hyperploid pmc's showed higher chiasma frequencies than non-doubled euploid pmc's (table 5).…”

“…This is probably due to duplication of homologues in hyperploid pmc's and perhaps also in hypoploid pmc's. However, if homoeologous pairing is suppressed in hexaploid Hordeum species by a "hemizygous ineffective" locus (Subrahmanyam, 1978) or one like the wheat Ph locus (Riley and Chapman, 1958), elimination of relevant chromosomes may remove, or duplication of others overcome, the suppression of homoeologous pairing. This possibility, itself, justifies further study of the present interspecific hybrids since removal of this obstacle may open the way for the transfer of genes between Hordeum, Triticum and Secale by meiotic recombination.…”

Cytogenetic analysis of three Hordeum x Elymus hybrids

“…The latter two values are not indicative of either autosyndetic pairing among H genome chromosomes or between homoeologous associations between H parental genomes . The level of bivalents in this hybrid approximated that observed in a trihaploid of H. parodii (Subrahmanyam, 1978) and was somewhat lower than in the H. parodii (6 x (Fedak, 1983 ;Gupta & Fedak, 1985b) . Similarly in intergeneric hybrids with S .…”

“…Third, the hybrid progeny from H. parodii (HHHHHH) x E. scabriglumis (SSHH??) showed significant increase in chromosome pairing over that of Occasional quadrivalents and pentavalents were also detected Gupta &Fedak, 1985b ;b Fedak, 1983 ;Subrahmanyam, 1978 autosyndetic pairing in trihaploid H. parodii individuals . The high level of pairing and multivalent formation can be easily explained by assuming the genomic constitution of E. scabriglumis to be SSHHHH .…”

CHROMOSOMAL INSTABILITY IN A HYBRID BETWEENHORDEUM VULGAREANDSECALE VAVILOVII

“…,jlrhrrturn x S. c~c~rculr (Morrison and Rajhathy , 1959;Wagenaar, 1959). The complete elimination of Scc.cilc chromatin from Hordc.lrrn x See-cilc hybrids leaving haploids of Hordrlrm has been reported (Kruse, 1969;Fedak, 1977a) which may be caused by a chromosome elimination mechanism similar to that reported in Hordrlrrn (Rajhathy and Symko, 1974;Subrahmanyam and Kasha, 1973;Subrahmanyam, 1978;Fukuyama and Takahashi, 1976). The variation in chromosome number of somatic and meiotic cells observed in the present study may be due to the incomplete expression of a chromosome elimination mechanism.…”