Linkages of the Aba (Albumin a) locus 
with markers of the linkage group VI

  

Swiecicki, W.K., Przybylska,  J., and               Institute of Plant Genetics, Polish Academy of Sciences

Zimniak-Przybylska, Z.,                                                       Poznan, 60-479 Strzeszynska 34, Poland

                                                                                                                                                    

 

       Investigations of seed proteins in the genus Pisum have identified the gene Aba for Albumin a and suggested a weak linkage with Pl on linkage group VI: joint chi square = 11.6; Cr-O = 39.3 (2). An electrophoretic screening of crude seed albumin extracts from over 500 Pisum accessions, representing a wide range of genetic and geographic variation, resulted in detection of 11 electrophoretic seed albumin patterns (3, 4). The patterns (phenotypes) were numbered from I to XI according to their sequence of discovery (1, 4).  Using successive letters for the albumin alleles seems to be practical because differences in the phenotypes are due to the occurrence of seven bands forming different sets.  For this reason it is not possible to designate the alleles according to electrophoretic mobility of respective electrophoretic variants as in the case of allozymes.  Phenotypes V, X, XI were observed only in P. fulvum (3, 4). Phenotypes I to X are believed to be alleles of a single locus, with test crosses showing co-dominant inheritance.

      In order to define the position of the locus more precisely, we performed another genetic analysis of Aba.  The line Wt 11777 from the Polish Pisum Gene Bank was selected and used in the cross.  It is the tester line for linkage group VI expressing the following markers: Pl, Arg (lower arm) and wlo art1 (upper arm) and the allele AbaA controlling electrophoretic seed albumin pattern I.  Line Wt 11777 was crossed to Wt 501 (albumin phenotype II and the suggested symbol AbaC). Unfortunately, Wt 501 expresses, in common with Wt 11777, the dominant allele at Pl. As a consequence in the F2 generation of K. 1880 (Wt 501 x Wt 11777) only the segregation of Arg Wlo Art1 and Aba were observed.

        Table 1 shows undisturbed monohybrid segregation for Aba and the marker genes. Table 2 presents results of observations of a dihybrid segregation. Arg does not display significant linkage with Aba at the level of precision available in the experiment, thus indicating that Aba is not close to the PlArg segment. Substantial deviations from independent assortment were found for gene pairs localized in an upper portion of the linkage group VI, i.e. Art1-Wlo but also Art1-Aba and Wlo-Aba. Calculated Cr-O values show clear linkages of the Aba  with both markers.  Comparison of linkage intensities suggests that Aba may be the most distal marker of those examined, but the data are not conclusive.

  

Table 1.  Monohybrid segregation for genes from the linkage group VI in the linkage test cross K. 1880 (F2 generation) – Wt 501 (Aba-c) x Wt 11777 (Arg wlo art1 Aba-a). 

Gene

Allele

Total

Chi square

(3:1)1

Dominant

Recessive

Arg

104

34

138

0.01

Art1

99

39

138

0.78

Wlo

99

39

138

0.78

Aba

108

41

149

0.50

 1Phenotypes of Aba-c were added to heterozygotes.

 

Table 2.  Distribution of phenotypes in F2 generation and the linkage test for K. 1880 – Wt 501 (Aba-c) x Wt 11777 (Arg wlo art1 Aba-a).

Pair of genes

Phase

Phenotype

Total

Joint chi square

Cr-O value + SE

(per cent)

DD

Dr

rD

rr

Arg-Art1

R

69

35

30

4

138

6.82

31.8 ± 7.5

Arg-Wlo

R

68

36

31

3

138

9.28

27.4 ± 7.8

Arg-Aba

R

70

34

29

5

138

4.74

35.6 ± 7.3

Art1-Wlo

C

88

11

11

28

138

50.99

16.6 ± 3.5

Art1-Aba

C

88

11

11

28

138

50.99

16.6 ± 3.5

Wlo-Aba

C

82

17

17

22

138

21.35

26.9 ± 4.5

 

1.  Blixt, S. and Przybylska, J.  1988.  Genet. Pol. 29: 33-39.

2.  Blixt, S., Przybylska J. and Przybylska-Zimniak, Z.  1980.  Genet. Pol. 21: 153-161.

3.  Przybylska, J.  1986.  Seed Sci. & Technol. 14: 529 – 543.

4.  Przybylska J., Zimniak-Przybylska, Z. and Górecka, D.  1992.  Genet. Pol. 33: 97-100.