Polymorphism of esterase isoenzymes of ripe seeds of samples of radish (Raphanus sativus L.)

A biochemical approach was used to assess the genetic variability of the seed radish ( Raphanus sativus L.) accessions which are distinguished by a wide variety of morphological characters. It is known that the esterase complex in plants has intraspecific specificity; in addition, these enzymes are characterized by tissue specificity. Earlier, the samples of the collections of the genetic resources of the radish were never evaluated for the presence of isozyme forms of esterases in mature seeds of this culture. The establishment of the general variability of isoenzyme systems and the identification of their genetic control make it possible to reveal the subtle mechanisms of the organism's relationship with the environment and homeostasis, which is especially important for long-term storage of samples in genetic seed collections. The development of effective biochemical markers for the rapid assessment of collection, as well as genetically and breeding significant material is also essential. This work allows us to fill the gap that exists in relation to the samples of genetic resources of the radish. From the collection of the Federal Research Center Vavilov All-Russian Institute of Plant Genetic Resources (VIR), 49 radish accessions were selected, belonging to three subspecies, divided according to geographic principle as Chinese, Japanese and European radish. All esterase isozymes of seeds were separated using native vertical electrophoresis in polyacrylamide gel followed by processing for nonspecific esterase. According to their esterase composition, all accessions were subdivided into 7 zymotypes, differing from each other by the presence or absence of certain zones. In total, in the esterase complex of radish seeds, 5 main isozymes with different molecular weights varying from 45.3 kDa to 35.0 kDa were found. All five zones were characterized by a high level of polymorphism among the samples. Based on the composition of isozymes, all genotypes formed 7 zymotypes. Zymotype No. 1, represented by the maximum number of esterases (5 zones), comprised of 43 % of the total number of genotypes. Zymotype No. 2 constituted 33 % of all samples. The rarest zymotypes No. 5 and No. 7 (4 %) differed in the minimum amount of esterase enzymes (2 zones each). Zymotypes No. 2 and No. 4 were characterized by 4 zones. Representatives of two groups, No. 3 and No. 6 had 3 zones in their esterase complex. The quantitative ratio of all esterase zones varied greatly in the studied samples. The minimum content (4.78 %) was found for the B5 zone, the maximum amount (67.44 %) was found for the B1 zone. The prevalence of each zone among all studied samples ranged from 13 to 23 %. Zones B3 (Mr = 39.7 kDa) and B4 (Mr = 37.1 kDa) were the most common among all esterase isozymes; these zones were observed in 23 % of genotypes. For 22 % of representatives, the B2 zone was characteristic (Mr = 42.9 kD). Zones B1 (Mr = 45.3 kD) and B5 (Mr = 35 kD) were less common, 19 % and 13 %, respectively. The average heterozygosity of isozygous forms of esterases of the studied radish samples was H total = 0.212, with variance for the same samples Var ( H total) = 0.0007. Cluster analysis of esterase enzymes divided the studied set of radish samples into European and Asian subspecies and varieties, and together with phenotypic traits, it allowed constructing a dendrogram corresponding to the botanical, agrobiological and geographical location of the samples. It should be noted that the accessions of the European subspecies radish are located in two clusters, and the accessions of Russian origin form a separate group in the first cluster, and the samples of European origin are grouped in the third cluster which also includes Japanese radishes of European origin. Perhaps this division is associated with the peculiarities of the selection process in creating these samples. Based on the data obtained, esterase enzymes are recommended as biochemical markers in genetic selection experiments.