Symbiotic locus Sym38 is localized in linkage group V.
Koroleva T.A., Voroshilova V.A., Lab. of Genetics of Plant-Microbe Interactions
Tsyganov, V.E., Borisov A.Y. and All-Russia Res. Inst. for Agric. Microbiology
Tikhonovich I.A. St.-Petersburg, Russia
Three independent mutations have been isolated in symbiotic gene sym38: RisFixF [1, Duc, Sagan, pers. comm.], SGENod--4 and SGENod--8 [2,3]. It was shown that those mutations block infection thread growth inside root hair [3].
For localization of locus Sym38 on genetic map the mutant line SGENod--4 was crossed with multiply marked line NGB1238. F1 and F2 plants had full fertility. Two independent populations F2 (SGENod--4 x NGB1238) were analyzed. In the first F2 population segregation by morphological markers d, le, s, wb, k, b, tl, Fs and Ust were analyzed and segregation by locus Sym38 was analyzed in F3 plants to identify F2 plants homozygous and heterozygous by WT and mutant alleles of Sym38. As a result, linkage between symbiotic locus Sym38 and Tl of linkage group V was observed (Table 1). In the second F2 population segregation by marker loci R, Tl and Gp of linkage group V and Sym38 was analyzed and again linkage between Sym38 and Tl (Table 1) was shown. However, barely significant linkage between Sym38 and Gp and no linkage between Sym38 and R were observed (Table 1). Previously in this linkage group symbiotic loci Sym16 [4] and Sym27 [5] were localized. Further mapping experiments are necessary to position the symbiotic locus Sym38 in certain segment of linkage group V accurately.
Table 1. Joint segregation data in the F2 populations of crosses 1) NGB1238 (tl) x SGENod--4 (sym38), 2) NGB1238 (tl, r, gp) x SGENod--4 (sym38).
|
Cross |
Locus pairs |
Phase |
Number of progeny with designated phenotype1 |
Total |
Joint c2 |
Prob |
RCV |
SE |
||||||||
|
A/B |
A/h |
A/b |
h/B |
h/h |
h/b |
a/B |
a/h |
a/b |
||||||||
|
1 |
Tl–Sym38 |
C |
17 |
11 |
3 |
5 |
31 |
6 |
0 |
17 |
18 |
108 |
46.5 |
<0.0001 |
23.3 |
3.4 |
|
2 |
Tl–Sym38 |
C |
20 |
|
6 |
|
|
|
2 |
5 |
15 |
83 |
29.2 |
<0.0001 |
18.8 |
4.7 |
|
R–Sym38 |
R |
41 |
|
20 |
|
|
|
20 |
|
2 |
83 |
4.7 |
<0.05 |
28.9 |
9.9 |
|
|
Gp–Sym38 |
R |
41 |
|
19 |
|
|
|
19 |
|
1 |
80 |
5.6 |
<0.025 |
22.4 |
10.5 |
|
1 A/a first gene; B/b second gene; h, heterozygous. When both genes are dominant, the capital letter stands for the dominant allele. When the second gene is codominant, the capital A stands for the dominant allele of the first gene and capital B for an allele of the second gene in coupling with A. When both genes are codominant, the capital letter stands for an allele of the first parent. The calculations have been made using Rozov’s program, CROS.
Acknowledgements: This work was supported by RFBR (01-04-48580 and 01-04-49643) and the Netherlands Organisation for Scientific Research (NWO 047-007.017).
1. Engvild, K.J. 1987. Theor. Appl. Genet. 74: 711-713.
2. Tsyganov, V.E., Borisov, A.Y., Rozov, S.M., and Tikhonovich, I.A. 1994. Pisum Genetics. 26: 36-37.
3. Tsyganov, V.E., Voroshilova, V.A., Priefer, U.B., Borisov, A.Y. and Tikhonovich, I.A. 2002. Ann. Bot., submitted.
4. Kneen, B.E., Weeden, N.F. and LaRue, T.A. 1994. J. Hered. 85: 129-133.
5. Rozov, S.M., Borisov, A.Y., Tsyganov, V.E., and Kosterin, O.E. 1999. Pisum Genetics. 31: 55-57.