V. 1. Revised linkage maps of barley, 1981.
T. Tsuchiya, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, U.S.A.
Progress in linkage mapping has been slow in the past year with a limited amount of information available for accurate gene location in barley chromosomes. However, some new information has been obtained in barley chromosomes, especially the structure of telocentric and acrotrisomic plants. This information has some significance in developing linkage maps.
1. Identification of chromosome arms in telotrisomics (Singh and Tsuchiya, 1981).
Complete analysis of telocentric chromosomes in telotrisomic lines by an improved Giemsa N-banding technique (Singh, 1981). All nine telocentric chromosomes were identified as telo 1L, 1S, 2L, 2S, 3L, 3S (new), 4L, 5L, and 6S. This result indicated that previously designated telo 3S is now telo 3L, and the newly obtained telocentric in chromosome 3 is designated as new 3S. Also previously designated telo 4S is now telo 4L.
Based on these results the long arm-short arm relationship for chromosomes, 3 and 4, was reversed (Fig. 1).
Figure 1. Linkage maps of barley, 1981.
2. Discovery of segmental deficiency in telocentric chromosome of two telotrisomic lines.
An improved Giemsa N-banding technique (Singh, 1981) also contributed to the finding of a segmental deficiency in two telotrisomic types, Triplo 2S and 4L (Singh and Tsuchiya, 1981). Some Triplo 2S plants showed about 33% deficiency in their telocentric chromosomes, while other plants showed normal telocentric chromosome for 2S. Similarly, most of Triplo 4L (previously 4S) showed some 23% deficiency in their telocentric chromosomes.
These findings suggest that some of the data from genetic analysis in these two telotrisomic lines may have been misleading in mapping genes in that particular arm of these chromosomes. However, the linkage maps will not be changed until new data are obtained from the critical experiments presently in progress by the present writer and his associates.
A new system for nomenclature and gene symbolization is being proposed (BGN 11:1-16). However, the linkage map (Fig. 1) presented in this volume shows previously established symbols.
The list of genes which are associated with chromosomes but not definitely located was again given in Table 1 with slight modifications from that of 1980 (Tsuchiya, 1980).
References:
Singh, R. J. 1981. An improved Giemsa N-banding technique for the identification of barley chromosomes. BGN 11:84-85.
Singh, R. J. and T. Tsuchiya. 1981. Preliminary studies on identification of telocentric chromosomes in telotrisomic barleys by Giemsa N-banding technique. BGN 11:71-74.
Tsuchiya, T. 1980. Linkage maps of barley, 1980. BGN 11:95-98.
