Genetical control and linkage relationships of Isozyme markers in sugar beet (B. vulgaris L.). 2. NADP- and NAD-specific malate dehydrogenases, 6-P-gluconate dehydrogenase, shikimate dehydrogenase, diaphorase and aconitase

Abstract

The NADP-specific malate dehydrogenase isozymes were controlled by multiple gene systems. Three genes coding for dimeric enzymes segregated in a dependent fashion (NADP-Mdh 1, NADP-Mdh 2, NADP-Mdh 3). A fourth gene (NADP-Mdh 4), also coded for dimers, but was not polymorphic in B. vulgaris. A fifth gene (NADP-Me 1) coded for enzymes active as monomers. Two genes were found to control the main zone of NAD-specific malate dehydrogenase: one coded for dimers (Mdh 1), while a second (Mdh 2) was not polymorphic in the assessions studied. 6-P-Gluconate dehydrogenase was not polymorphic in B. vulgaris; the two types detected on SGE1 electrophoresis were due to developmental expression of the different systems. No genetical segregations could be detected in progeny of crosses of the distinct phenotypes. A shikimate dehydrogenase gene (Skdh 1) that coded for monomers was identified. The diaphorase system was rather complex, but one gene (Dia 1) coding for monomeric enzymes could be identified. Aconitase was found to be controlled by two independent genes (Aco 1, Aco 2), both polymorphic and coding for proteins active as monomers. Tight linkage was found between the genes NADP-Mdh 1, NADP-Mdh 2 and NADP-Mdh 3. Linkage was also found between a pollen fertility restorer (Z) and the Mdh 1 gene. The identification of linkage with Aco 1 needs further investigation. R segregated independently from Mdh 1, Aco 1 and Dia 1. Independent segregations were scored for isozyme genes Pgm 2, Icd 1, Ak 1, Gpi 1, Aco 1 and Dia 1.

Linkage maps for nine isozyme and four marker loci in sugarbeet (Beta vulgaris L.)

“…The results presented here confirmed the linkage, previously reported, of R and Idh z (Smed et al, 1989;Wagner et al, 1992), of Mdhl and a restorer gene (Van Geyt et al, 1990;Wagner et al, 1992), and of Gdh 2 and Mdh~ (Konovalv, 1988). New linkages were also determined between Idh~ and B, Skdh 2 and a restorer gene, Akt and Lap, Pgm z and Mdh3, and Pgm z and M. Seven of the nine isozyme loci tested were assigned to four linkage groups, R-BIdh z, Gdhe-Mdh I, AkrLap, and Mdh~-Pgm z.…”

“…This is in good agreement with the recombination value of 12.7% reported by Wagner et al (1992). The different gene symbols have been assigned to the restorer gene linked to Mdht; Z by Van Geyt et al (1990) and X by Wagner et al (1992). The genetic explanation is very confused, especially for the gene action of both restorers under S cytoplasm.…”

“…Allele designation for Gdh 2, Idhp Lap, Mdh~, and Pgm I was consistent with those used by Abe (1991) and Abe & Shimamoto (1989). Genetic interpretations of isozyme phenotypes have been presented by Abe & Tsuda (1987) for Gdh 2 and Lap, Smed et al (1989) for Akl, Idhl and Pgi 2 (designated Gpi 2 in their report), Aicher & Saunders (1990) for Pgm~ and Mdh 3, Van Geyt et al (1990) for Mdh~ and Skdh 2 (designated Skdh in their report). TA33 was monomorphic for the nine isozyme loci tested, the genotype of which was Ak122, Gdh23~,Idh122,Lap 33,Mdhy,Mdh322,Pgi222,Pgm122, and Skdh222.…”

“…Furthermore, the alleles of most isozyme loci interact in codominant fashion, and also they rarely exhibit epistatic interactions (Tanksley & Rick, 1980). Inheritance of isozymes has been reported for several enzyme species in sugarbeet (Van Geyt & Jacobs, 1986;Abe & Tsuda, 1987;Konovalv, 1988;Smed et al, 1989;Aicher & Saunders, 1990, Van Geyt et al, 1990Wagner & Wricke, 1991). However, there are few reports on their linkage relationships.…”