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 Aba^A controlling electrophoretic seed albumin pattern I.  Line Wt 11777 was crossed to Wt 501 (albumin phenotype II and the suggested symbol Aba^C). 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 Pl—Arg 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). 

 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).

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.