II.6 Approximate position of the chlorina mutants f4f4 and f8f8 on chromosome 1.
R.F. Eslick Department of Plant & Soil Science, Montana State University, Bozeman, MT. 59715, U.S.A.
An lk2 n msg1O tester stock was used in crosses with f4 or f8 stocks or derived genotypes of these two mutants. As the opportunity has arisen over a period of years, data on smaller populations have accumulated and are summarized. The values in parenthesis following the phase represent the number of times F1's were grown in different environments and included in the summaries. Progenies of several F1's may have been grown under any given environment.
The data of Table 1 are taken from crosses of f4f4 stocks only and the data of Table 2 from crosses of f8f8 stock only. The percent recombination is determined by maximum likelihood. The chi-squares given are for the fit of the calculated recombination value to the summed classes used in maximum likelihood calculations.
Table 1. Recombination data from crosses involving the chlorina mutant f4f4
We have previously shown the gene order on chromosome 1 to be lk n msg1O, Eslick, et al. (1971) and (1972). f4f4 data presented in Table 1 may be mapped as in figure 1.
In a F2 repulsion cross of 283 individuals, Walker, et al. (1963) reported three individuals of nn f4f4 genotype and a recombination percentage of 20.4 + 6.2.
In this report of the same type of cross, no recovery of the nn f4f4 genotype was noted in a population of 682 individuals and the recombination value was calculated as 0.1% + 3.8.
Tsuchiya and Singh (1973) found f4 and f8 to be on the long arm of chromosome 1 with n.
The f8f8 data of Table 2 may be mapped as follows:
Table 2. Recombination data from crosses involving the chlorina mutant f8f8.
Robertson (1967) reported the following recombination values for f8f8: f8 and n, 13.0 + 0.8%; f8 and ac2 18.0 + 0.7%; f8 and yc, 39.8 + 1.2%; and f8 and fc, 44.3 + 0.3%. The above map is not inconsistent with this gene ordering.
It was not possible to positively place f4 relative to n or f8 relative to msg1O by comparing observed data with single cross and double cross expectancies. Data are presented in Table 3.
Table 3. F2 genotype frequencies in 3 and 4 point tests with f4 and f8.
*Note that these ratios will be distorted because of a failure to classify msglO msglO F2 plants for genotype.
Eslick, R.F., E.A. Hockett and G.D. Kushnak (1972). Recombination values of four genes on chromosome 1, BGN2: 123-126.
Eslick, R.F., M.M. Rahman and C.W. Crowell (1971). Gene ordering near the centromere of chromosome 1, BGN1: 20-22.
Robertson, D.W. (1969). Linkage studies with five naturally occurring chlorophyll mutations in barley (Hordeum species). Can. J. Genet. Cytol. 9: 321-326.
Tsuchiya, T., and R.J. Singh (1973). Further information on telotrisomic analysis in barley. BGN3: 75-78.
Walker, G.W.R., J. Dietrich, R. Miller and K. Kasha (1963). Recent barley mutants and their linkages II. Genetic data for further mutants. Can. J. Genet. Cytol. 5: 200-219.
BGN 6 toc
BGN Main Index