VARIABILITY OF CYTOGENETIC INDICATORS OF SEED OFFSPRING OF WALNUT (JUGLANS REGIA L.) DURING INTRODUCTION IN THE VORONEZH REGION

Abstract

The article discuss the results of cytogenetic studies of seed offspring of walnut (Juglans regia L.), which is an introduced species in the Voronezh region. Modern ideas about the level of adaptation of introduced plants should be based on an assessment of the cytological foundations of heredity of seed progeny. This will make possible to reveal the level of stability of the genetic system of plants growing outside the habitat conditions usual for a given species. Nuts of the 2017 harvest were collected from mother plants of 30-35 years of age of seed origin, growing on private farmsteads in Voronezh. To study the cytogenetic characteristics, squashed preparations were prepared according to the standard technique. The following cytogenetic characteristics were studied in the root meristem of seed seedlings: mitotic activity, cell fractions at various stages of mitosis, the level and spectrum of mitosis pathologies, the size of nucleoli and the spectrum of their types, and the occurrence of cells with a persistent nucleolus at the stage of metaphase, anaphase and telophase of mitosis. Statistical data processing was performed using the statistical software package Stadia 7.0 Professional (InCo, Russia) and MedCalc 17.5.3. (MedCalc Software, Osten, Belgium). The presence of three polymorphic groups of seedlings according to the studied cytogenetic parameters was revealed: mutable (with a high level of pathological mitosis), low-mutable (with a low level of cytogenetic disorders), and intermediate. The cytogenetic characteristics for each of the selected groups of seedlings were described in detail. The mechanisms of homeostasis maintaining at the cellular level are discussed for above polymorphic groups. A small proportion of seedlings with a high level of cytogenetic abnormalities (7.5 %) and the predominance of seedlings with average (70 %) and low (22.5 %) values of pathological mitoses indicate a high degree of adaptation of the parent trees of the introduced walnut to the environmental conditions of the Voronezh region. Using ROC-analysis, predictors have been established for assigning any seedling to one of the selected model groups (mutable or low mutable). These predictors were: the proportions of cells at the prophase and metaphase stages, the level of pathological mitoses with and without prophase, the frequency of vacuolated and compact nucleoli. The obtained data of cytogenetic studies can be used to develop recommendations for improving the system of seed production and selection of new forms of walnuts.