The cultivation of wheat landraces in the Ethiopian highlands dates back ca. 5000 years (Feldman 1976). Conceivably, such wheats represent one isolated group of the earliest cultivated forms after the formation of the amphiploid(s). Although they showed little variation for gross karyomorphology (based on arm ratio), meiotic studies have revealed the presence of reciprocal translocations. Moreover, a remarkably high sterility was observed in some intervarietal/ intraspecific hybrids (Belay et al. 1994; Belay and Merker 1997).
The main objectives of the present study were; (1) to investigate
C-band polymorphism in seven tetraploid wheat landrace morphotypes
(=genotypes) of Ethiopian origin and, (2) to identify translocation
breakpoints in five of them that are known to carry one reciprocal
translocation each, relative to the standard Italian durum wheat
variety, Senatore Capplelli (Belay and Merker 1997). We also compared
our previous karyomorphology studies in non-banded chromosomes (Belay
et al. 1994) with the results from C-banded ones.
Materials and methods
Plant material
Seven tetraploid wheat morphotypes, namely K-1-1, B-3-33, B-3-11,
CD-7, A-4-34, A-1-116 and DZ-04-118 (an improved landrace variety
through mass selection) were used. Their collection history and some
of their morphological characteristics are given in Belay et al.
(1994). Except for A-4-34 and A-1-1 16, all differed by one
translocation each from Senatore Cappelli (SC) (Belay and Merker
1997), which was also included here for comparison purposes. The AB
genome chromosomes of SC are structurally similar to those of the
hexaploid cytogenetic reference, Chinese Spring (Perera et al. 1983).
Seeds of SC were kindly supplied by Prof. Carla Ceoloni, Viterbo,
Italy.
Cytology
The C-banding procedure employed was that of Gill et al. (1991) with
minor changes. Band@nomenclature followed that of the same authors.
For each morphotype, a minimum: of five metaphase plates from, at
least, four plants each were analyzed. The karyotypes were compared
mainly with those of the AB- genome chromosomes of hexaploid wheat
varieties reported by Friebe and Gill (1994). Arm ratio (long/short)
was calculated based on the mean of six homologous pairs of each
chromosome as measured from enlarged photomicrographs. The results
were compared with those reported by Endo and Gill (1994) and
Landgeva et al. (1995). Whenever the mean arm ratio of a certain
chromosome lied out of the range reported by these authors, Student's
t-test was performed with its counterpart chromosome in SC.