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Pisum Genetics |
Volume 24 |
1992 |
Research Reports |
pages 14-15 |
A new ramosus gene on chromosome 5
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Apisitwanich, S.
Swiecicki, W.K.
Wolko, B.
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Department of Genetics, Kasetsart University Bangkok, Thailand Inst, of Plant Genetics, Polish Academy of Sciences Poznan, Poland Plant Experiment Station, Wiatrowo Wagrowiec 62100, Poland |
The ramosus mutant rms was obtained by Blixt (2) after X-irradiation of the cv. Parvus. The locus is on chromosome 3 (2). The mutant allele has several pleiotropic effects: there are many basal branches, the stems are hard, seemingly more lignified, and the peduncles are shortened (2).
In 1982, a mutant with a similar phenotype to rms was found in the M2 population of cv. Porta treated with 170 r Nf. Segregation of our mutant in the M2 family, in the F2 of a cross between the mutant and its initial line, and in other crosses (Table 1), indicated monogenic recessive inheritance. The mutant line was included in the Pisum Genetics Stocks at Wiatrowo in 1985 under the catalogue number Wt15244. The locus identity cross between Wt15244 and the type line for rms (Wt15237) gave normal F1 plants, i.e. both mutants are controlled by different loci. In accordance with Arumingtyas et al (1) we propose symbol rms-5 for the new gene with Wt15244 as type line.
To test for linkage, line Wt15244 was crossed with marker lines Wt10345, Wt11143, Wt11288 and Wt11540 from the Wiatrowo collection. These lines have morphological markers for chromosomes 2-6. In addition, we analysed segregation for the isozyme loci Idh (chr. 1), Pgm-p (chr. 2), Pgd-c and Acp-1 (chr. 5), and Aat-m, Pgm-c and Pgd-p (chr. 7). Significant deviations from random assortment were found only in the F2 population of cross Wt15244 x Wt11540 (Table 1) where the ramosus locus showed significant linkage with gp, Acp-1 and Pgd-c which are located on the lower half of chromosome 5 according to the recent map of Weeden et al (3). The data indicate that rms-5 is located on chromosome 5, most probably between Gp and Pgd-c as shown below.
For more precise mapping, more markers should be considered for this segment, namely, lk, cri and creep. We will also try to obtain results from a larger population of cross Wt15244 x Wt11540. The present data (Table 1) show a small but significant (P < 0.05) excess of gp and Pgd-cs segregates.
Table 1. Phenotypic distribution in an F2 population from cross Wt15244 (rms-5 Gp Pgd-cf Acp-1f) x Wt11540 (Rms-5 gp Pgd-cs Acp-1s)
Monohybrid segregation
|
Locus |
Phenotype* |
c2 (3:l) |
||
|
D |
R |
Total |
||
|
Rms-5 |
78 |
19 |
97 |
1.5 |
|
Gp |
62 |
32 |
94 |
4.1 |
|
Pgd-c |
64 |
33 |
97 |
4.2 |
|
Acp-1 |
62 |
26 |
88 |
1.0 |
Dihybrid segregation
|
Loci |
Phenotype* |
c2 |
Recomb. fract. |
SE |
Phase |
||||
|
DD |
DR |
RD |
RR |
Total |
|||||
|
Rms-5/Gp |
44 |
32 |
18 |
0 |
94 |
11.5 |
18.7 |
9.9 |
R |
|
Rms-5/Pgd-c |
45 |
33 |
19 |
0 |
97 |
12.2 |
18.2 |
9.8 |
R |
|
Rms-5/Acp-1 |
43 |
26 |
19 |
0 |
88 |
10.2 |
19.8 |
10.2 |
R |
|
Gp/Pgd-c |
53 |
9 |
8 |
24 |
94 |
33.9 |
17.6 |
4.4 |
C |
|
Gp/Acp-1 |
53 |
7 |
7 |
19 |
86 |
32.4 |
16.5 |
4.4 |
C |
|
Pgd-c/Acp-1 |
56 |
6 |
6 |
20 |
88 |
39.8 |
13.8 |
4.0 |
C |
* D = homozygous dominant or fast + heterozygous plants; R = homozygous recessive or slow plants.
Arumingtyas, E.L., Floyd, R.S., Gregory, M.J. and Murfet, I.C. 1992. Pisum Genetics 24:17-31.
Blixt, S. 1976. Agri Hort. Genet. 34:83-87.
Weeden, N.F., Ambrose, M. and Swiecicki, W.K. 1991. Pisum Genetics 23 Cover.