Lancaster Y. Source material for courgette breeding (Cucurbita pepo L.) with high adaptive potential and resistance genes to courgette yellow mosaic virus (ZYMV)

The dissertation is devoted to the theoretical substantiation and practical solution of the scientific problem of breeding process optimization for courgette lines growing combining high adaptive potential based on the quantitative traits that determine the fruit productivity and quality as well as performing the genetic control of the expression level of the ZYMV resistance gene. The scientific novelty of the research is that, for the first time in Ukraine, polymorphism of the eukaryotic transcription factor eIF4E in various representatives of the Cucurbitaceae family, associated with the formation of resistance to pathogens of the Potyvirus family, was investigated. The degree of homology of the gene of the eukaryotic transcription factor eIF4E in various species and genera of plants related to courgette, which plays a key role in the formation of resistance of courgette to harmful viruses of the Potyvirus family, was determined. Based on the reference sequence XM_023685756.1, the design of primers to the complete exon and intra-exon sequence of the eIF4E gene was developed to evaluate its expression. Primer testing allowed identification of target amplicons of 143 and 830 bp. Based on the in silico polymerase chain reaction, the expression of the squash eIF4E gene was confirmed in Defender F1, Best of British F1 and Eight Ball F1 hybrids with CDS and EXP primers to the sequence XM_023663719.1. According to the results of molecular genetic analysis of the studied working collection of courgette, which consisted of 29 varieties and F1 hybrids of different geographical origins, 129 ISSR loci were identified, among which 109 were polymorphic. Unique DNA regions have been identified that can be used for the development of more specific markers, as well as markers of the corresponding genotypes. For the study of molecular genetic polymorphism of courgette, 13 highly informative ISSR primers were selected, which detected the level of polymorphism at the level of 62.5–100.0%. A stress-tolerant linear material of courgette of different geographical origin has been created for adaptive breeding in the conditions of the agro-climatic growing zone of the Eastern Forest-Steppe of Ukraine. 6 lines of courgette (LK 17-8, RVL-19, VL-90, VL-91, VL-92, Vedi) were transferred to the national genetic bank of plants, which exceeded the standard variety Chaklun in terms of the level of manifestation of a number of valuable economic characteristics: general and commercial productivity; duration of the fruiting period; the content of biologically valuable components in fruits.