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Cytogenetics of the viral pathogenesis in crop plants


Author: Andronic Larisa
Degree:doctor habilitat of biology
Speciality: 03.00.15 - Genetics
Year:2021
Scientific consultant: Maria Duca
doctor habilitat, professor, Moldova State University
Institution: Institute of Genetics, Physiology and Plant Protection of the ASM

Status

The thesis was presented on the 27 January, 2021
Approved by NCAA on the 26 February, 2021

Abstract

Adobe PDF document – 2.15 Mb / in romanian

Thesis

CZU 575:578.76:631.526

Adobe PDF document 10.37 Mb / in romanian
284 pages

Keywords

cytogenetics, crop plants, viruses, meiotic recombination, somatic recombination, protein markers, microsporogenesis, viral pathogenesis, ultrastructure, genetic variability

Summary

Thesis structure: The thesis consists of an introduction, 6 chapters, general conclusions and recommendations, a bibliography composed of 490 titles, 8 annexes, 209 pages of basic content, 45 tables, 54 figures. The obtained results were published in 74 scientific papers.

Field of study: Plant Genetics

The aim of the research: elucidation of the impact of viral agents as inducers of genetic variability and establishment of the cytogenetic effect of viral pathogenesis in crop plants based on the particularities of mitotic and meiotic proliferations in host-pathogen compatible systems.

Objectives: identification of changes induced by viral infections in differentiated and actively dividing cell systems in crop plants (barley, tomato, cabbage) infected with RNA or DNA viruses; establishment of the particularities of meiotic and mitotic divisions in various host-pathogen systems; evaluation of the viral agents impact on the process of meiotic and somatic recombination depending on the particularities of the host-pathogen system; determination of the specificity of cell division processes in offspring obtained under conditions of viral pathogenesis; estimation of genetic variability in infected plants and their progenies; assessment of the genotoxicity of viral agents in host plants; identification of the mechanisms involved in the genetic variability induction; elaboration of procedures for induction, appreciation and selection of useful variability based on the application of viral infection as a recombinogenic factor.

Scientific novelty and originality: the concept of genetic effect produced by viral infections in susceptible hosts, that confirm the possibility of phytoviruses using as inducers of variability, conducting to the internal structure, transcription and translation, affection of proliferative processes, gene expression, and traits variation was argued. The confirmation of the involvement of viruses, comparable to physical factors (gamma rays), in changing genes expression, increasing of the recombination spectrum and expanding of genetic variability, reconformations that can be transmitted to the offspring of infected plants.

The main new results for science and practice: Pathogenesis caused by TAV, PXV, TMV, BSMV and CaMV established macro- and microstructural changes in infected cells (assimilation and protective tissues), as well as in free of viral germs (arhesporale and meristematic tissues), expressing specific and stereotypical reactions. The cellular differentiated sensitivity was established at the compatible tissues level on vegetative and reproductive organs and incompatible for viral particles (microspores). The impact of viruses on the chromosomes conjugation, and the distribution of genetic material between daughter cells comparable to gamma rays was demonstrated; destabilizing effect of microsporogenesis on virus-infected tomato and barley were established, that condition increased asynchronism and acceleration of the meiosis promotion; established the genotoxic and mitogenic effect of RNA viruses in hosts and offspring of infected plants that include changes in the somatic recombination, disruption of mitotic divisions, changes in the expression of genes involved in antioxidant metabolism (APX and SOD) and pathogenesis-related proteins (PR-3, PR-5 and PR-10); the nucleopathic effect was proved, expressed by chromatin reconformations for DNA virus.

The theoretical significance of the work: the response of plants to viral infections on ultrastructural level is expressed by specific reorganizations, which can serve as a criterion for the pathogen detection, and nonspecific, manifested based on the principles of typical transformations, reflecting the pathogenicity of the viral agent; the impact of viral infections on susceptible hosts conditions a wide range of reactions that accentuate the cell divisions asynchronism and heterogeneity of morpho-functional and genetic changes. Specific deviations of the expression of genes involved in antioxidant metabolism (APX and SOD), pathogenesis-associated proteins (PR), depending on the pathosystems specificity can be used in identification of genotypes with different sensitivity to the viral agent.

Applicative value: The procedures for inducing genetic variability in crop plants (tomato, barley, cabbage) were elaborated, with the application of viral infection as recombinogenic factor and appreciation of diversity based on protein (hordein), enzymatic (peroxidase, esterase) and molecular (PR-5) markers. Implementation of scientific results: the elaborated procedures were applied in diversification of the spectrum of genotypes with agronomical valuable quantitative characters and obtaining new varieties of tomatoes; the scientific results served as support for courses Cell Biology, Plant Histology and practical works Cytological methods for cell and tissue evaluation (cycles I and II), MSU.