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PNL Volume 20
1988
RESEARCH REPORTS
LINKAGE BETWEEN Dia-1 AND LOCI ON CHROMOSOME 3
Wolko, B. and N. F. Weeden
NYS Agricultural Experiment Station,
Geneva, NY 14456 USA
Enzymes catalyzing the reaction:
NADH + acceptor = NAD + reduced acceptor can be v i s u a l i z e d a f t e r
horizontal starch gel electrophoresis by using an assay consisting of 100 ml 0.1 M Tris HC1 pH
8 . 5 , 40 mg NADH, 40 mg MTT and 1 mg 2,6 dichlorophenol i n d o p h e n o l . At least four
NADH diaphorases (DIA) isozymes can be resolved in pea leaf extracts, and we have found
v a r i a t i o n in t h e m o s t anodal isozyme DIA-1 and the most intensely staining isozyme DIA-3
( Fi g. 1 ) . The DIA-1 polymorphism is best resolved u s i n g the pH 6.5 h i s t i d i n e buffer
system of Cardy et al. (1), whereas the DIA-3 v a r i a t i o n is m o r e c l e a r l y o b s e r v e d on a
Tris b o r a t e - E D T A s y s t e m ( 2 ) . In a s u r v e y of a wide sample of P i s u m germplasm,
we identified at least 2 common variants for DIA-1 the more anodal of which we d e s i g n a t e d
"a" and t h e other "b". We demonstrate here that the variation in DIA-1 phenotype shows
monogenic i n h e r i t a n c e , being encoded by a locus that e x h i b i t s linkage with markers near
M on chromosome 3.
Marker lines fixed for DIA-la were crossed with lines fixed for DIA-lb, and the r e s u l t i n g
h y b r i d s s e l f e d to form F2 p r o g e n i e s . Segregation for DIA-1 phenotype was observed
in each of the four F2 progenies analyzed (Table 1). In three of the four progenies the DIA-1
variants behaved as c o d o m i n a n t a l l e l e s at a single segregating locus, which we designated
Dia-1. The f o u r t h progeny d e r i v e d from the c r o s s A73-91 x PI 1 7 9 4 4 9 gave a l l t h r e e
of t h e expected phenotypes but the relative number of these was s i g n i f i c a n t ly d i f f e r e n t
from the e x p e c t e d 1:2:1 ratio. J o i n t s e g r e g a t i o n a n a l y s i s of the loci segregation in
these progenies i n d i c a t e d l i n k a g e b e t w e e n D i a - 1 and loci near M and chromosome 3
(Table I I ) .
Previous results indicate that Aat-c is about 15 map u n i t s from M and Lap-2 (3).
C o m p a r a t i v e map d i s t a n c e s and the lack of l i n k a g e between Dia-1 and Acp-3 or St
( r e s u l t s not p r e s e n t e d ) suggest that Dia-1 is located about midway between Lap-2 and Aat-p
on the d i s t a l side of M from the centromere. The a v a i l a b i l i t y of t w o common alleles at
Dia-1 should make this locus very useful in f u r t h e r mapping s t u d i e s .
This work was supported in part by a grant f r o m the I n t e r n a t i o n a l Board of Plant
Genetics Resources (Grant #86/102).
1.
2.
3.
Cardy, B. J., C. W. Stuber, and M. M. Goodman. 1980. Dept. of Statistics Mimeo Series No.
1 3 1 7 , North Carolina S t a t e Univ., Raleigh.
Shaw, C. R. and R. Prasad. 1970. Biochem. Genet. 4: 297 -320.
Weeden, N. F. and G. A. Marx. 1987. J. Hered. 78:153-159.
PNL Volume 20
1988
RESEARCH REPORTS
53
**Significant at P<0.01.
Phenotypic designations: a = allozyme a, b = allozyme b, h = both allozymes „
present. Parental phenotypes. Not calculated because of distorted segregation
ratios (see Table I).
Fig. 1.
(a) Diaphorase phenotypes on histidine gel, pH 6.5.
(b) Diaphorase phenotypes on tris-borate-EDTA gel, pH 8.0.
Anode is at top of each photograph.
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