AN ALLOZYMIC POLYMORPHISM IN PEA MALATH DEHYDROGENASE_IS SPECIFIED BY A LOCUS ON CHROMOSOME 1

PNL Volume 18 1986 RESEARCH REPORTS

AN ALLOZYMIC POLYMORPHISM IN PEA MALATH DEHYDROGENASE_IS SPECIFIED BY A

LOCUS ON CHROMOSOME 1

E. Pagowska, and Institute of Plant Genetics

Polish Academy of Sciences, Poznan, Polanl

N.F. Weeden NYS Agricultural Experiment Station)

Geneva, NY US

Polymorphism in the malate dehydrogenase (L-malate NAD oxido reductase

EC 1.1.1.37; MDH) phenotype has been previously reported in pea (4,5,7) and

attributed to genetic differences among the lines examined. However

genetic tests confirming this assumption have not been published, although

the genetic basis of MDH polymorphism has been established in Zea mays (6),

He1ianthus annuus (1), and Cucurbita pepo (2). In this communication we

present data demonstrating that the variation observed in one region of the

MDH zymogram exhibits Mendelian segregation. Comparison of the MDH

segregation pattern with segregation at other loci indicate that the locus

responsible for the MDH variation is located on chromosome 1.

To obtain the MDH phenotype, leaf extracts were subjected to horlzon-

tal starch gel electrophoresis using a histidine buffer system at pH 6.5 as

described previously (9). The assay solution (25 ml) contained the follow-

ing: 0.1M Tris-HCl pH 8.5, 1 5 mg L-malate, 5 mg NAD, 3 mg MTT and 0.5 mg

PMS. Assays for other isozyme systems have been described (9). The paren-

tal lines used for the genetic analysis were A1078-234, B777-248, A1078-239

(all obtained from Dr. G.A. Marx) and PI 358612 (obtained from the NW

Regional Plant Introduction Station at Geneva).

The variation observed in the MDH phenotype is shown in Fig. 1. Line

PI 3586 12 (and B777-248) displayed an MDH band with an R of about 0.25

(MDH-4 in Fig. 1), whereas the other 2 lines lacked this band. Crosses

between lines possessing the MDH-4 isozyme and those lacking such a band

gave Fl plants exhibiting a discernable, although often slightly less

intense, MDH-4 band. In segregating F2 populations we did not attempt to

differentiate between the heterozygous and homozygous MDH-4 "plus"

phenotypes but divided the plants into 2 categories, those exhibiting the

MDH-4 band and those lacking it.

The MDH segregation data from 2 different crosses closelv fits a 3:1

ratio expected for monogenic control (Table !). We suggest that this locus

tentatively be designated Mdh. There are probably other loci coding MDH

isozymes but further characterization of the MDH system is required before

more appropriate locus designations can be made.

Joint segregation analysis revealed non random assortment between Mdh

and 2 isozyme loci on chromosome 1 (Table 2). Both Aat-p and Est-3 have

been mapped near A (3,8) and our data indicate that Mdh also should display

linkage with this morphological marker. Mdh segregated independently of D

Idh, and I, the other chromosome 1 markers segregating in one or both of

the crosses listed in Table 1 (data not shown).

1. Kahler, A.L. and C.L. Lay. 1985 J. Hered. 76:335-340.

2. Kirkpatrick, K.J., D.S. Decker, and H.D. Wilson. 1985. Econ. Bot.

39:2 89-2 99.

3. Mahmoud, S.H., J.A.Gatehouse, and D. Boulter. l984. Theor. Appl. Genet.

68:559-566.

4. Muller, H.P. 1976. PNL 8:42-44.

5. Muller, H.P. 1980. PNL 12:57-58.

6. Newton, K.J. and D. Schwartz. 1980. Genetics 95:42 5-442.

7. Weeden, N.F. 1983. PNL 15:58-59.

8. Weeden, N.F. 1985. In: The Pea Crop. pp. 55-66. P.O. Hebblethwaite,

M.C. Heath, and T.C.K. Dawkins, eds. Butterworths, London.

9. Weeden, N.F. and G.A. Marx. 1984. J. Hered. 75:365-370.



PNL Volume 18 1986 RESEARCH REPORTS		55



	Fig. 1. Malate dehydrogenase pheno- types from leaf extracts of the hybrid produced from the cross A1078-239 x PI 358612 (lanes 1 and 2), of the Al078-239 parent (lanes 3 and 4), and of the PI 358612 parent (lanes 5 and 6). Migration is toward the anode at top of figure.