| Identification of a wheat-Agropyron and a wheat-rye
chromosome substitution F.J. ZELLER Technische Universitat Munchen, Institut fur Pflanzenbau und Pflanzenzuchtung, 805 Freising - Weihenstephan, Federal Republic of Germany Introduction There are several examples of alien substitution lines in hexaploid wheat in which the alien chromosome has been derived from related genera of the sub-tribe Triticinae (see for ref. ZELLER and FISCHBECK 1974). In 1958 KNOTT described a wheat strain with a chromosome from Agropyron elongatum (HOST) BEAUV. carrying a genetic factor for blue aleurone colour. Most of the already identified wheat-Agropyron substitution lines are substitutions for eliminated chromosomes of the wheat D-genome (BAKSHI and SCHLEHUBER 1959, QUINN and DRISCOLL 1967, KNOTT 1958, LARSON and ATKINSON 1970). From these results it was inferred that the aforementioned wheat-Agropyron line is a substitution for a chromosome of the wheat D-genome. Wheat strain 205-70 is characterized by a pubescent peduncle. Since rye chromosome 5R bears the gene for hairy neck, the transfer of hairy neck to wheat must have occurred either by a translocation or by a substitution involving 5R and a wheat chromosome. O'MARA (1946), DRISCOLL and SEARS (1965), SEARS (1967), BIELIG and DRISCOLL (1970b), and ZELLER and BAIER (1973) have shown that rye chromosome 5R is genetically related to wheat chromosomes of the homoeologous groups 4 and 5. Therefore one of these wheat chromosomes was suspected of being involved in the wheat-rye chromosome substitution of strain 205 - 70. Material and Methods A wheat strain (F4) called 'Blue Dark' from a cross between Thatcher and 'Blue A' was kindly supplied by Dr. D.R. KNOTT (Canada). Blue A was developed from the back-cross Rescue (2n=42) x Agropyron elongatum (2n =70) x Rescue (KNOTT 1958). The Chinese Spring lines MT (monotelosomic)-1D, MT-3D, mono-4D, MT-5D and mono-6D were crossed with Blue Dark. Then the chromosomes of the F1 hybrids were counted in root-tip meristem cells and the chromosome pairing analyzed in PMC's of the first meiotic metaphase. The somatic chromosomes were pretreated in monobromonaphthalene. Root tips and anthers were hydrolyzed in 1N HCl and stained in basic fuchsin. The strain 205 - 70, kindly provided by Dr. KISS of Hungary, was derived from a hybrid (F7) of Triticale Hadmers-leben (2n=56, Prof. VETTEL) and Ottawa wheat (KISS, pers. communication). This strain was observed mitotically in the somatic cells and then crossed with disomic Chinese Spring, disomic Kolibri and the aneuploid Chinese Spring lines mono-4A, MT-4B, mono-4D, MT-5A. MT-5B and MT-5D. The pairing configurations of the disomic and monosomic F1 hybrids were analyzed cytologically. Results and Discussion The pairing configurations of the meiotic metaphase chromosomes in the monosomic F1 hybrids between five Chinese Spring aneuploids and the strain Blue Dark are summarized in Table 1. In the mono-1D, 3D ,5D and 6D hybrids most frequently PMC's with chromosomes forming 19 bivalents and three univalents were observed. The commonest chromosome configuration in the mono-4D cross, however, was 20 bivalents and one univalent (Table 1). From these conflgurations it may be concluded that wheat chromosome 4D in Blue Dark has been eliminated and replaced by a specific chromosome from Agropyron elongatum. LARSON and ATKINSON (1973), using a wheat-Agopyron triple-alien-substitution line that was derived like Blue Dark from a hybrid between Triticum aestivum L. var. Rescue and Agropyron elongatum (2n=70), obtained similar results. In an attempt to select the corresponding three single disomic substitutions from the triple substitution line LARSON and ATKINSON (1970) found that the 4D disomic substitution is characterized by seeds with blue aleurone. |
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