CHROMOSOME RELATIONSHIPS IN INTERSPECIFIC AVENA HYBRIDS, WITH SPECIAL REFERENCE TO HYBRIDS WITH A. LONGIGLUMIS

Abstract

Wide variation of chromosome pairing configurations was observed at metaphase I proper in each F₁ hybrid of A. strigosa (2n=14), A. barbata (2n=28), A. sativa (2n=42), A. fatua (2n=42) and A. sterilis (2n=42) crossed with A. longiglumis (2n=14) as given in Tables 1-5.
Inspection of the data suggests an occurrence of a maximum pairing configuration of two associations of 6, and 8 chromosomes in A. longiglumis (AlAl, genome formula)× A. strigosa (AsAs) as well as two associations of 10 chromosomes and one univalent in A. barbata (AsAsBrBr)×A. longiglumis (AlAl). The chromosome associations can be formed as the result of the structural differentiation of the longiglumis genome, probably characterized by two single and three reciprocal translocations.
It is also sure that the second genome (Br) of A. barbata (AsAsBrBr) is partially homologous with both of the As and Al genomes. Their homology relationships are illustrated in the scheme showing structural differentiation of chromosomes (Fig. 1). It is largely similar to that proposed by Holden (1966) although much modified.
In the hybrids between A. longiglumis (AlAl) and hexaploids (general genome formula is AhAhChChDhDh) the chromosome behavior can be understood by assuming intergenomic chromosome pairing of Al-7-Ah-3-4-ChDh (Ch-3-4-Dh). It is very similar to As-7-Ah-4-ChDh (Ch-2-Dh) expected from the data observed by Kihara and Nishiyama (1932) in hexaploids×A. strigosa.
Thus the evidence supports the view that several different genomes were derived from a common ancestral genome in the course of evolution of the genus Avena.