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Number 72: 104-105 (1991)
Isozyme
and chromosome polymorphisms of the genus Avena
and its geographic distribution in Morocco
T. Morikawa
College of Agriculture, University of Osaka Prefecture, Sakai,
Osaka, 591 Japan
All the biological species of Avena with the exception of
A. damascena coexist in the area roughly between Southern
Spain, Morocco and the Canary Islands. The most probable area of
origin of the polyploids is where the putative lower ploidy ancestors
and their higher ploidy descendants overlap. Clearly Southern Spain,
Morocco and the Canary Islands represent the only area which meets
such a demand. Four species, A. canariensis(2x), A.
agadiriana(4x), A. maroccana(4x) and A.
longiglumis(2x), in total 41 populations of the
genus Avena were collected from the Canary Island and Morocco
sponsored by the International Board for Plant Genetic Resources. In
order to clarify genetic diversity within and between wild species of
Avena, isozyme and chromosome variations were examined.
Avena canariensis is restricted to the Canary islands
especially the islands of Fuerteventura and Lanzarote. I recorded and
average of 53.8% variable loci,1.76 alleles per locus and an
expected heterozygosity of 0.226 in that from Fuerteventura but which
values of Lanzarote were less than those of Fuerteventura. The
populations from northern Lanzarote where is xeric rocky mountain
area were monomorphic but had peculiar allozyme. The intraspecific
variation of A. canariensis as indicated by morphological
plasticity, variation of chromosome shape and isozyme polymorphism,
has further been emphasized by a pair of satellite-deficiencies, very
irregular cytomixis and a reciprocal translocation. These cause often
meiotic irregularities and distort the structures or disrupt the
process to bring about varying degrees of sterility or aberrant
gametes. The term "meiotic drive" has been coined to characterize a
preferential survival or perpetuation. A. canariensis has
distinctive ecotypes, which are divided into early and late types.
The late ecotype is having a late heading date, prostrate growth
habit and pubescence whilst the early ecotype is early, erect and
glabrous. These growth habits are positively correlated with isozyme
and chromosome genotypes. The early type always had Est-3S,
Est-2N, Got-3M and Pgi-2F alleles, whilst the late type
had Est-3F, Est-2F, Got-3S and Pgi-2S. The same trend
was observed in the satellite chromosome numbers. The early ecotype
always had a pair of satellite chromosomes whilst the late ecotype
always having two pairs of those. The early maturing types were
distributed throughout the islands and were adapted mainly to
disturbed habitats along ditches and roadsides. The later maturing
types were collected in the southern part of Fuerteventura and the
northern part of Lanzarote, mainly at high elevations in habits that
were basically undisturbed by cultivation.
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