StatusThe thesis was presented on the 23 January, 2020
Approved by NCAA on the 31 July, 2020
Abstract– 2.13 Mb / in romanian
4.03 Mb /
The thesis includes introduction, four chapters, general conclusions and recommendations, the bibliography with 328 sources, 103 pages basic text out of 137 total pages, 10 tables, 33 figures. The obtained results are published in 18 scientific papers.
Field of study: 164.2 - Plant physiology The purpose of the paper consists in evaluation of the physiological and molecular changes associated with plant resistance against broomrape attack as the scientific basis for breeding programs and improvement of sunflower cultivation technologies in the Republic of Moldova.
Research objectives: Histochemical analysis of cell wall reinforcement in sunflower root cells within compatibility and incompatibility systems with O. cumana; Evaluation of defensive response by estimation of the activity of some enzymes (phenylalanine ammonia-lyase, superoxide dismutase and ascorbate peroxidase) at different stages of artificial infection with O. cumana; Quantitative mRNA expression of genes involved in reinforcement of cell wall, metabolism of superoxide and peroxide radical; Integrative analysis of histological, biochemical and molecular patterns for validation and assessment of their use in breeding strategies.
Novelty and scientific originality: Extensive evaluation of histological (accumulation of lignin and callose), biochemical (activity of phenylalanine ammonia-lyase, superoxide dismutase and ascorbate peroxidase) and molecular (expression of genes involved in cell wall reinforcement and synthesis of antioxidant enzymes) changes in susceptible and resistant sunflower genotypes have been performed at five developmental stages of broomrape under conditions of artificial infestation. Based on the positive correlations between gene expression, enzymatic activity and accumulation of secondary metabolites, for the first time it was found that common mechanisms involved in the fortification of cell walls were triggered as a defensive reaction in all genotypes, being expressed at different developmental stages. The resistance of genotype Favorit (Or6 gene; race F) against broomrape is ensured by the early manifestation of the response reaction (35 days) and the subsequent homeostatic maintenance of all investigated parameters. The activation of mechanisms from phenylpropanoids and glucans pathways in the genotype PR64LE20 (race H) is found much later (67 days) and it is supplemented by the activity of antioxidant enzymes.
The obtained results that contribute to solve an important scientific problem consist in scientific foundation of the current knowledge related to the non-specific mechanisms of plant resistance to holoparasite infection, in dynamics, which contributed to the formulation of scientific principles as a basis for improvement of sunflower cultivation technologies in the Republic of Moldova, allowing their application in breeding and obtaining of resistant hybrids by using gene donors from resistant genotypes.
Theoretical significance. The study represents a fundamental methodological basis that deepen the knowledge related the mechanisms of resistance of the sunflower against broomrape; the reinforcement of cell walls to prevent pathogen invasion; the role of antioxidant enzymes in maintaining of redox status and ensuring the response to broomrape attack.
Applicative value of the work. Integrative approach of the results obtained at the histological, biochemical and molecular level represents a theoretical and fundamental basis for the direction of plant breeding and plant protection against root pathogens. Also, some information completes the courses of Botany and Phytopathology (aspects of broomrape life cycle), Plant physiology (resistance mechanisms) and Genetics (gene interaction). It is recommended to use the genotype Favorit as a gene donor for strategies of obtaining resistant hybrids in the breeding programs oriented to non-specific resistance.
Implementation of scientific results. The obtained data serve as a scientific material in the teaching of the course of Phytopathology and Plant Physiology. Developed specific primers are recommended for testing the expression profile of sunflower germplasm to broomrape resistance.