II.46 Primary trisomic analysis of lg 3 (light green) and f3 (chlorina) in barley.
T. Tsuchiya, T. Fachan and T.E. Haus. Department of Agronomy, Colorado State University, Fort Collins, Colorado 80523, U.S.A.
The association of a chlorina gene (lg 3, light green) with chromosome 4 has been questioned mainly because; (1) a limited amount of information is available which was obtained from conventional genetic analysis (Immer and Henderson, 1943; Robertson et al, 1947). (2) difficulty in identification of the stock for lg 3 since the symbol lg 3 was subject to a rather complicated change (Robertson et al, 1947). Since an attempt of obtaining the original stock for lg 3 ( and lg 2) failed, primary trisomic analysis has been conducted with the stocks available in the Barley Genetic Stock Center in Fort Collins, Colorado, U.S.A.
Robust, the trisomic for chromosome 4 in the variety SE 16 was crossed with a homozygous plant for lg 3. F2 populations were analyzed in both diploid control and the trisomics. Chromosome number was counted in all plants in F2 population from trisomic F1 hybrids.
These results show that the gene lg 3 is located in chromosome 4. The occurrence of one recessive homozygote in the 2x + 1 portion suggests that the gene lg 3 is located far from the centromere. Telotrisomic analysis is now under way to find arm location of lg 3.
Chlorina 3 (f3) is a good light green mutant first reported by Immer and Henderson (1943). The gene f3 has shown that it is not allelic to any of the designated chlorina genes (f, f2, f4, f5, f6, f7, f8, f9, and fc) (Tsuchiya et al. 1973). This gene would be a good marker when it is located in its chromosome. Two trisomics were crossed with the chlorina 3 (f3). Segregation ratios were recorded in F2 generations as shown in Table 2.
Table 2. Segregation ratios in F2 generation of crosses between trisomics and f3 stock.
Triplo 4 showed a disomic ratio. The segregation in Triplo 7 is not clear. The trisomic section seems to show trisomic ratio since there are no recessive homozygotes. However, the segregation in the 2x portion and total population fits 3:1. The apparent trisomic ratio in the trisomic section may be ascribed to the small number of plants in this F2 population. More plants are needed to obtain definite conclusions.
References:
Immer, F.R. and M.T. Henderson. 1943. Linkage studies in barley. Genetics 28: 419-440.
Robertson, D.W., G.A. Weibe and R.G. Shands. 1947. A summary of linkage studies in barley: Supplement I, 1940-1946. J. Am. Soc. Agron. 39: 464-473.
Tsuchiya, T., D.A. Jensen and T.E. Haus. 1973. Allelism tests of some chlorina mutant genes of barley. BGN, 3: 71-72.
