The experiment was conducted to characterize 78 radish genotypes using esterase and peroxidase isoenzymes. The results of the experiment reveal a wide range of diversity among the genotypes based on their esterase and peroxidase isoenzyme banding patterns. Five bands at different relative front (Rf) values varying from 0.06 to 0.56 were observed in peroxidase enzyme system and formed 10 zymotypes. Zymotype P₁ was the most frequent which includes 26.92% of the total genotypes. The lowest frequency of 2.56% was observed in the zymotype P₁₀. Bands 3 and 4 consist of same frequency (23.31%) of the genotypes at Rf values 0.20-0.30 to 0.30-0.50. It was also found that there was no common band for all the genotypes. Thus, the genotypes have a wide range of genetic variation. On the other hand, 13 electrophoretic zymotypes (P₁-P₁₃) were observed in the esterase enzyme system formed by 13 bands at different Rf values varying from 0.04 to 0.93. It appeared that electrophoretic zymotype P₆ was the most frequent (25.64%) and zymotype P₁₃ was the least frequent (2.56%). The zymotype P₁₁ had maximum number of bands. From the distribution of esterase bands among the radish genotypes, it was observed that band 3 had the most frequency of 18.75%, followed by bands 2 and 4 which had the same frequency of 16.67% among all the genotypes. A dendogram, based on the two polymorphic enzyme activities of all the genotypes, was classified into eight major clusters, designated as I, II, III, IV, V, VI, VII and VIII. The highest number of 21 genotypes was found under the cluster number I that represented 27% of the total genotypes, followed by cluster VI which contained 17 genotypes. The lowest number (4) of genotypes was found under cluster VII, followed by cluster III which contained 5 genotypes. The results indicate that zymotypes of higher frequency are the representative of less variation. The lower frequency of the germplasm in different zymotypes indicated higher variation among the genotypes.

Radish is the second major vegetable crop in terms of area and the first major winter vegetable crop, in Bangladesh, in terms of production. It is widely cultivated in the cool season of Bangladesh. Its production can be boosted up by utilizing hybrid technology. Thus, the development and use of new hybrid varieties can increase the yield potential of radish, compared to the production of traditional varieties (Tyagi, 1972). Molecular marker is an important tool for crop improvement and marker-assisted selection for traits of interest. The different molecular forms of an enzyme which catalyze the same reaction are called isozymes if they or their polypeptide constituents are coded by more than one gene locus, and allozymes when coded by different alleles of the same locus (Gottlieb, 1981). In other words, isozymes have been defined as different variants of the same enzyme having identical or similar function and present in the same individual (Markert and Moller, 1959). In plants, most enzymes routinely assayed have several isozyme forms often with specific subcellular locations and a majority of isozymes have different allozymic variants. Isozymes play an important role in numerous aspects of biological studies in plants (Harris, 1966; and Tanksley and Orton, 1984). Isozymes, the molecular form of a protein, can be differentiated by electrophoresis. The primary evidence observed in studies of protein electrophoretic variation is a band of color in an acrylamide gel. Electrophoretic data in plants have often been used to accumulate information about genes per se for the purpose of describing the amount and pattern of genetic variability in population and the extent of divergence among them and between species. Electrophoretic analysis of an isozyme has been used extensively to provide rapid and quantitative estimates of the extent of genetic variation within the species (Bailey, 1983; and Tanksley and Orton, 1984). The conventional methods used for identifying different crop plants are based on the phenotypic expressions of the plant, plant parts, or seeds. Such expressions are strongly influenced by the environment. Thus, these conventional means are gradually being replaced with chemical methods. One of the main methods is isozyme electrophoresis by which the chances of correct cultivar identification are highly improved.

Considerable variability with respect to root shapes and quality of radish is available in this country. Such variability can be confirmed through isozyme analysis. Till date, there has been no report on such studies on radish. Therefore, the isozyme study was carried out for two-enzyme system to know the banding pattern among the parents and hybrids and also the inheritance pattern of parental bands by all the hybrids indicating the authenticity of the hybrids of radish.

Genetics & Evolution Journal, Isozymic Variations, Protein Electrophoretic Variations, Electrophoresis, Electrophoretic Data, Radish Genotypes, Electrophoretic Zymotypes, Vegetable Crops, Polymerization, Isozyme Banding Patterns.