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Materials and methods
A total of 135 strains of T. araraticum, 47 from Turkey, 67
from Iraq, 4 from Iran and 17 from Armenia were used (for strain No.,
see Table 1). All the materials were
maintained by controlled selfing at the Plant Germplasm Institute,
Faculty of Agriculture, Kyoto University. Detailed passport data of
the materials are listed in the Catalogue of the Institute (Tanaka
1983). These strains were intercrossed and chromosome pairing
patterns of the hybrids were observed at first meiotic metaphase (MI)
by the acetic-orcein squash method. Seventeen strains were further
analyzed by C-banding; chromosome preparation and C-banding technique
were described earlier (Badaeva et al. 1994).
Results and discussion
Reciprocal translocations in T. araraticum and their
geographical distribution. Based on the analysis of chromosome
pairing at first meiotic metaphase of intraspecific hybrids (detailed
data not shown), strains were grouped into 15 chromosome types as
listed in Table 1. Seventy nine strains
were grouped into T1 type and meiosis was normal with 14
bivalents in hybrids within this type. This was regarded as standard
chromosome structure because the majority (58.5%) of the strains
examined belonged to this group. Types T2 to T7
differ from T1 by one translocation, T8 to
T14 differ from T1 by two and T15
had three translocations relative to T1 (Table
2). Thirty five strains were tentatively classified as
unidentified. They have one or two translocations relative to
T1 but the chromosome type was not determined due to the
lack of several cross combinations with other chromosome types.
Table 3 summarizes the geographical
distribution of each chromosome type. T1 is found in all
the regions where this species was sampled, while the derived types
were mostly restricted in a single locality. Types T2,
T3, T9 and T10 were found in
Armenia. The remaining ten types were found in Iraq. Two types,
T4 and T6, were not restricted to a single
site. 8567 and 8572 of T4 were found in Sulaymaniyah,
Iraq, and the third strain, 8732 was collected in Rowanduz, Iraq. The
two strains of T6, 8714A and 8719, were collected at two
sites in Rowanduz, Iraq. Apparently, strains with certain structural
rearrangements have a wider geographical distribution as also
reported by Badaeva et al. (1994). This further suggests that derived
types other than T4. and T6 also are found in
two or more localities if more strains of T. araraticum are
examined.
Identification of chromosomes involved in translocations.
Chromosomes involved in each translocation were estimated from the
occurrence of multivalents among 15 translocation types. Chromosomes
involved in the translocation between T1 and T2
were numbered as 1 and 2. Chromosomes of other translocations were
numbered successively based on the presence or absence of common
chromosomes involved in translocations as summarized in Table
4. For example, T2 and T3 have one
translocation relative to T1, and forms a sexivalent in
hybrids between them (Table 2). Thus
translocations of these two types share a pair of chromosomes in
common. This shared pair of chromosomes was arbitrarily assumed as 1
and the translocation of T3 assigned as 1 and 3. In some
cases, two or more translocations occurred independently on the same
chromosome pair. T4 have 4-5 translocation and
T8 have two translocations, 3-4 and 4-5. If these two
types share a common 4-5 translocation, a quadrivalent will be
observed at MI in the hybrid T4 x T8. However,
since a sexivalent was found we concluded that the 4-5 translocation
carried by the two types had a different origin.
Karyotypes of 17 strains representing 15 chromosome types were
further analyzed by C-banding. Chromosomes were identified according
to the genetic nomenclature (Badaeva et al. 1991, Gill et al. 1991).
By combining two types of data, pairing and banding, it was possible
to identify chromosomes involved in these translocations completely
(Table 4). However, only two chromosomes,
2At and 5At, were identified genetically in the
A genome because others lacked marker bands. Then, the remaining four
At chromosomes were tentatively numbered from
Atl to At4.
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