Fifty-four single translocations, induced by -rays in 6 cultivars of winter barley were listed by Gramatikova (1992). Using a spring barley translocation tester set from A. Hagberg, Svalöv, Sweden, the involved chromosomes were identified in each case.
Further progress was made in localizing translocation breakpoints to specified regions of somatic metaphase chromosomes by computer-assisted karyotype analyses of Giemsa N-banded chromosomes. Some of the break positions were found to be located in rather distal chromosome regions. This revealed several translocations with improved efficiency in linkage studies (Marthe and Künzel, BGN 23 ___)
Ninety-one balanced tertiary trisomic (13TT) spring barley stocks from Gatersleben are added to the World Collection (Tables 1 and 2). The BTTs, resulting from extensive efforts to use msg genes for hybrid seed production (Scholz and Künzel 1987), are well adapted and cytogenetically highly stable with trisomics rather viable under field conditions. Shortawnedness was incorporated into some of the BTT stocks for increasing the tendency to allogamy.
For stock designation a numerical code of five figures is used, with the first three figures referring to 'basic' BTT systems as defined by particular genes and translocated extra chromosomes, specified in column 2 and 3 of Table 1. The fourth and fifth figures numbering the stocks of a system. The material is maintained in long-term storage.
Table I compiles 40 stocks belonging to 25 systems. Some key informations are included. Table 2 contains 51 stocks of 14 'basic' systems, out of the 25 listed in Table 1. Those are additionally balanced for a recessive lethal gene. Hence, the tertiary extra chromosome carries the dominant normal allele of a lethal, in addition to the dominant Msg allele, both closely linked to the breakpoint. This kills the disomic progeny of the BTT stock resulting in pure stands of trisomics. Linked lethal genes were obtained by quite special mutation experiments which resulted either directly in marked BTTs or, as intermediate products, in so-called LL (linked lethal) stocks. In these LL stocks a lethal is closely linked to an msg, i.e. in coupling . They were used in different ways (see column two of Table 2) to set up marked BTT stocks. Allelic tests between the BTT-included and other lethal genes were not performed.
Considering the balanced tertiary trisornics from Gatersleben together with the BTT material reported by R. T. Ramage in the preceding BGN volumes, the World Collection of BTTs harbours at present 120 stocks representing 47 different BTT systems characterized by a particular gene and a particular tertiary extra chromosome each. One system uses a shrunken endosperm gene, five systems use a seedling lethal gene and fourty-one systems use one out of nine different genes for male sterility (msgl, msg2, msg4, msg5, msg6, msg16, msg22, msg24, msg36). In addition, there are 59 BTT lines being balanced for an msg gene (msgl, msg4, msg6 and msg24) and an additional lethal gene. Furthermore, the Collection contains 8 stocks of 5 different systems where BTT-like segregations are caused by complex cytogenetic systems others than BTT as, e.g., by balanced types of telotrisomics or compensating trisomics involving translocation chromosomes. The chromosomal status of these systems is not yet fully elucidated in each case.
Tab.1 (con't.) BTT stocks from Gatersleben added to the World Collection
Gramatikova, M. 1992. Translocation lines of winter barley. BGN 21:25-26.
Künzel, G. 1984. Isochromosome for the short arm of barley chromosome 6. BGN 14:6-8.
Künzel, G. 1993. Coordinator's report: Translocations, balanced tertiary trisomics, desynaptic genes. BGN 22: in press.
Marthe, F. and G. Künzel. 1994. New barley translocation testers for linkage studies as revealed by computer-assisted breakpoint mapping on somatic chromosomes. BGN 23: ___.
Ramage, R.T. 1971. Coordinator's report: Translocations and balanced tertiary trisomics. BGN 1:74-80.
Scholz, F. and Chr. O. Lehmann. 1958. Die Gaterslebener Mutanten der Saatgerste in Beziehung zur Formenmannigfaltigkeit der Art Hordeum vulgare L.s.1.I Kulturpflanze VI:123-166.
Scholz, F and G. Künzel. 1987. Hybrid barley - problems and advance, especially in developing genetic systems. Barley Genetics V, Proc. Fifth IBGS Okayama 1986:937-943.