A search for tomato disease resistance genes using molecular markers to create new genotypes

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Background. The creation of tomato cultivars and hybrids with a complex of resistance genes is the main task of a breeder. This process can be accelerated through the use of molecular markers at the stages of initial forms selection and the offspring analysis. There is a large amount of information in the literature about DNA markers of resistance genes. Their significant part was recommended for the use in marker-assisted breeding. The purpose of our work was to screen a collection of tomato varieties and hybrids using molecular markers of genes for resistance to the most common diseases of open-ground tomato (late blight, root nematodes, tomato bronzing virus (TSWV)) and to identify gene sources for breeding work. The following markers were selected for research: Sw-5-2 (Sw-5b gene of resistance to TSWV), Mi23 (Mi1.2 gene of resistance to the root-knot nematode), 2 markers NC-LB-9-78 and NC-LB-9-79 (late blight resistance gene Ph-3). During the work, a collection of 46 accessions of tomato cultivars and hybrids was analyzed. Results. The molecular genetic analysis has yielded clear, reproducible fragments that corresponded to the expected ones. All the used markers were codominant. Analysis of the studied collection accessions found the analyzed genes to be polymorphic. The cultivars and hybrids F1 of tomato identified as promising for the use in breeding have resistance to root nematodes (F1 hybrids: A-01, ‘Imitator’, ‘Manon’, cultivars ‘Elegiya’ and ‘Buoy-Tur’), to tomato spotted wilt virus (TSWV) (F1 hybrids: A-01, ‘Manon’ and cultivar ‘Buoy-Tur’), and also to late blight (hybrids F1: А-01, ‘Azhur’, ‘Barin’, ‘Vlastelin stepej’, ‘Zhirdyaj’, Luchshij SeDeK, ‘Manon’ and cultivars: ‘Buoy-Tur’, ‘Zefir v shokolade’, ‘Zolotaya kaplya’, ‘Krasavec’, ‘Lodochka’, ‘Metelitsa’, ‘Alice's Dream’, ‘Sibirskij tigr’, ‘Slavyanskij shedevr’, ‘Elegiya’). It is advisable to use these accessions as sources of resistance genes. Based on the obtained data, five initial forms were selected for breeding and assessed for the intracultivar polymorphism of the studied genes. Cultivars ‘Krasavec’ and ‘Sibirskij tigr’ were used as parent forms. Their hybridization was carried out and hybrid forms homozygous for the dominant allele of the Ph-3 gene were obtained. Conclusions. The use of molecular markers in the conducted study allowed screening the collection of tomato varieties and hybrids for the presence of resistance genes to the most common diseases. Based on the obtained data, parental pairs were selected, hybridization carried out, and hybrid forms with the late blight resistance gene obtained.