BGN 2: Recombination values of four genes on chromosome 1 BARLEY GENETICS NEWSLETTER, VOL. 2, IV. REPORTS FROM COORDINATORS
Eslick et al., pp. 123-126

IV.1. Recombination values of four genes on chromosome 1.

R. F. Eslick, E. A. Hockett*, and G. D. Kushnak. Department of Plant and Soil Science, Montana State University, Bozeman, Montana 59715, U.S.A. (*Research Geneticist, Plant Science Research Division, ARS, U.S.D.A.).

Over the years we have accumulated recombination ratios in connection with our breeding programs. Within a given cross we rather consistently examine four or more families. This is to report progress to date on four genes, covered vs naked (Nn), fertile vs male sterile (Ms1Oms1O), full vs 1/2 awn (lk2lk2) and fertile vs male sterile (Ms14ms14). Pedigrees of crosses reported in tables 2, 3 and 5 are recorded in table 1. R. W. Allard's tables (Hilgardia 24:235-279, 1956) were used to calculate combined maximum likelihood recombination values utilizing all data.

Table l. Crosses used to determine recombination values.

Translocation data indicated that ms1O and ms14 loci were probably in the centromere region of chromosome 1 (R. F. Eslick, Barley Genetics II:292-297, 1971). From 3 point test data Eslick, et al., (BGN 1:20-22, 1971) showed the gene order to be:

lk2-n-ms10-ac2

From the data of table 2 the combined recombination value n-ms1O was calculated to be 7.2% + 0.41%. A homogeneity chi square of 63.880 with 16 degrees of freedom (P < .005) indicates this calculated recombination value does not fit all observed ratios equally well. Four of 22 families in the F3 of cross 19 were dropped to obtain 18 homogeneous families for these calculations.

Table 2. Segregation ratios for crosses involving covered and naked (Nn) and fertile and male sterile (Ms1Oms1O) on chromosome 1.

The combined recombination value of n-lk2 (table 3) was determined to be 7.9% + 0.32%. The homogeneity chi-square of 26.483 with 13 degrees of freedom (P.025-P.010) indicated that the recombination value of 7.9% did not equally apply to all crosses.

Table 3. Segregation ratios for crosses involving covered and naked (Nn) and full-awn and half-awn (Lk2lk2) on chromosome 1.

The calculated combined recombination value for lk2-ms10 was 14.7% + 0.71%. Homogeneity chi-square for fit to all crosses was 14.087 with 10 degrees of freedom and p lies between .250 and .100.

Based on the previous results with translocation breakpoints the balanced male steriles Ms1Oms14/ms1OMs14 were established. With independence a 9 fertile:7 male sterile ratio should be obtained. With no recombination in a repulsion cross the expected ratio would be 2:1. It will be noted that the observed ratio was much nearer 1:1 than 9:7, table 5. Since this cross provided little information the balanced male sterile x normal fertile cross was made, Ms1Oms14/ms1OMs14 x Ms10Ms14/Ms1OMs14. An Lk2Lk2 marker stock was used as the male to eliminate chance selfing. All F1's from this cross should be fertile and segregate male steriles if no recombination occurs.

One fertile F2 row and 98 F2 rows segregating male steriles were observed. The fertile row represents 1/2 of the recombination gametes and thus the approximate recombination value is 2% + 2%. We are attempting to recover the ms1Oms14 genes in coupling. This would provide a more critical test.

Working recombination percentages for the 4 genes reported would then be:

Table 4. Segregation ratios for crosses involving full-awn and half-awn (Lk2lk2) and fertile and male sterile (Ms1Oms1O) on chromosome 1.

Table 5. Ratios of fertile to male sterile from the balanced male steriles Ms1Oms14/ms1OMs14
 

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