A new Fix- mutation in pea shows linkage with group 3 marker M

Pisum Genetics

Volume 25

1993

Research Reports

page 45

A new Fix^– mutation in pea shows linkage with group 3 marker M

Rozov¹, S.M.,

Borisov², A.Y.,

Tsyganov², V.E., and

Tikhonovich², I.A.

Institute of Cytology and Genetics, Novosibirsk ,

630090, Russia

²Research Institute for Agricultural Microbiology,

Podbelsky Chosse 3, St. Petersburg-Pushkin 8,

189620, Russia

The recessive mutant Sprint-2Fix^– was isolated after chemical (EMS) mutagenesis from our laboratory line Sprint-20 (a, d, M, Fs). This mutation leads to the formation of white ineffective nodules without nitrogenase activity and to severe chlorosis of the shoot when the plant is grown on a nitrogen-free medium. Differentiation of bacteroids is morphologically unnoticeable; the symbiosomes have abnormal structure as they contain several bacteroids in one envelope (1).

An allelism test between the Fix^– mutant E135f (sym13; 3) and our Sprint-2Fix^– mutant showed that the two mutants are not allelic. Since allelism tests have not yet been made against six further Fix^– mutants (2, 4, 5), a gene symbol has not been assigned to the Sprint-2Fix^– mutant gene at this stage.

The mutant line Sprint-2Fix^– was crossed with testerline NGB1238. The F₂segregation data in Table 1 provide significant evidence (P = 0.0005) of linkage between the mutant gene in line Sprint-2Fix^– and the linkage group 3 marker M. None of the previously mapped symbiotic genes is located in this region of the pea linkage map (4, 6).

Acknowledgements. This work was supported financially by the Research Program INTERBIOAZOT and partially funded by the National Programs Frontiers in Genetics and Fundamental Biological Research.

Table 1. F₂ segregation data from cross NGB1238 (m, Fix⁺) x Sprint-2Fix^– (M, Fix^–).

Number of plants with phenotype				Chi-squared			Recomb. fract. ± SE
M Fix⁺	M Fix^–	m Fix⁺	m Fix^–	M–m	Fix⁺–Fix^–	Joint	Recomb. fract. ± SE
74	31	45	2	2.84	0.88	12.20*	21.4±7.7%

* P = 0.0005

1. Borisov, A.Y., Morzina, E.V., Kulikova, O.A., Tchetkova, S.A., Lebsky, V.K.
and Tikhonovich, I.A. 1992. Symbiosis 14:297-313.

2. Due, G. and Messager, A. 1989. Plant Sci. 60:207-213.

3. Kneen, B.E., LaRue, T.A., Hirsch, A.M., Smith, C.A. and Weeden, N.F. 1990.
Plant Physiol. 94:899-905.

4. LaRue, T.A. and Weeden, N.F. 1992. Pisum Genet. 24:5-12.

5. Postma, J.G., Jager, D., Jacobsen, E. and Feenstra, J.W. 1990. Plant Sci. 68:
151-161.

6. Weeden, N.F., Kneen, B. and LaRue, T.A. 1990. In: Nitrogen Fixation:
Achievements and Objectives, Eds. P.M. Gresshoff, J. Roth, G. Stacey and W.E.
Newton, Chapman and Hall, New York, pp. 323-330.

*Correspondence to: A.Y. Borisov; Fax 7 812 470 4362, Email chief@riam.spb.su