No abstract

The linkage relationship between eighteen isozyme loci and the morphological markers hypocotyl colour (R-r), monogerm character (M-m), pollen fertility (X) and stem fasciation (Verb.) are tested. Tliree linkage groups could be set up, involving all morphological marker loci and eight of the isozyme loci. Est-2, R-r, Fdp-2, Got2 and led-] belong to linkage group I, linkage group II includes the loci Fas-fas Mm, Est-3 and Aeo-1, linkage group III contains the loci X, Mdh-1 and Est-5.When analysing the inheritance of isozymes and RFLPs, deviations are usually found in some lines from the expected frequencies of a 3 : 1 or 1 : 2 : 1 segregation at single marker loci. In many cases these data can still be used for the estimation of recombination values with linked loci under the control of selection. Procedures to estimate linkage in such cases are given and applied to experimental data in Beta vulgaris.

Laboratory bioassays showed the occurrence of 8.5-fold resistance to cyhexatin and ca. 15-fold resistance to dicofol in laboratory-selected populations of European red mite (Panonychus ulmi (Koch)). Surveys, in 1984, of 45 orchards, using field-collected mites exposed to discriminating concentrations of cyhexatin or dicofol, detected resistance to cyhexatin in ca. 29% of the populations. Resistance to dicofol was identified in 2 of 45 assays.

Different origins ot Beta proeumbem and B. v:ebbiana, which are \^•lld species of the section Procumbentcs, were investigated b)" means of electropboreticai techniques. The iso2^"me patterns did not sho' "R' any differences between the two species. Assignment of accessions to either one of the two species was not possible using the differences occurring in the banding patterns of some enzyme systems. O'ne can raise the question, therefore, if the classification of B. prociimhens and H. ii'ebbiana into two species is justified.

Genetic markers are most useful in plant breeding but so far only a few morphological and isozyme markers are known in Beta vulgaris. In this paper, the isozyme systems aconitase (AGO), NADH-:dihydrolipoamiddehydrogenase (DIA), esterase (EST), fructose-1,6-bisphosphatase (FDP), and hexokinase (HK) were genetically analysed. Isoelectric focussing (IEF), vertical polyacrylamide gel electrophoresis (PAGE) and starch gel electrophoresis (SGE) were used to separate the isozymes. A total of eight loci could be identified. The allelic forms of Aco-1, Dia-1, Est-1, Est-5 and Hk-1 are active monomers. The gene products of Est-3 and Fdp-2 are active as dimers. Est-2 also showed allelic forms without activity; null-alleles.Molecular markers can be used in plant breeding for a range of purposes: genotype identification, control in breeding programmes, identification of chromosomes and gene marking by establishing linkage relationships with loci of agronomic importance (TANKSLEY and OR-TON 1983), In all cases, precise knowledge of the inheritance of such markers is useful for their application in plant breeding; in most cases it is indispensable.Isozymes represent one type of molecular marker; normally they are expressed codominantly so that all the different genotypes can be identified.This study describes the genetic analysis of five isozyme systems of sugar beet. Materials and MethodsThe original material consisted of diploid plants of Beta vulgaris L. Selfed progenies of single plants heterozygous for the isoenzymes to be investigated were used for genetic analysis. On average, more than 50 plants of each line were examined. Ghisquare analysis was used to test the segregation of single loci.Isozyme analysis was carried out with leaves from about nine-week-old seedlings. About 400 mg of fresh green leaf material was homogenized following the method of SCHMIDT-STOHN (1979) with 5 % sucrose and 0.1 % mercaptoethanol. Extracts were centrifuged at about 12,000 rpm at 4 °G for 8 min. The supernatant was directly used for isoelectric focussing (IEF), polyacrylamid gel electrophoresis (PAGE) and starch gel electrophoresis (SGE).Isoelectric focussing was used to separate esterase (EST) and NADH: dihydrolipoamide dehydrogenase (DIA) isozymes. Acrylamide concentration of the gels was 6 % T/3 % G and 5 % T/3 % G, respectively. IEF was performed in a pH 3.5-10 gradient. Electrode solutions were 0.5M H3PO4 (anode) and IN NaOH (cathode). lOjuI extract per individual were applied 6 cm and 1.5 cm, respectively, from the cathode. Separation conditions were 7 mA const, per gel and 1500 V (max.) at 10 °G for 2 hours.Hexokinase (HK) isoenzymes were subjected to electrophoresis in 8 % vertical polyacrylamid gels. Gel and electrode buffer was 125 mM Tris/19 mM boric acid, pH 8.9 (STEGEMANN et al. 1983). Separation conditions were 50 mA const, per gel and 360 V (max.) at 4 °G for 3.5 hours.AGO (aconitase) and FDP (fructose-l,6-bisphosphatase) isozymes were separated in 12 % starch gels. Electrode buffer was 0.22 M Tris/0.065 M citric acid, pH 7....