The paper presents the results of the evaluation of tomato lines obtained as a result of intraspecific hybridization based on resistance to high temperatures (40o, 42oC) in early ontogenesis. Seedlings grown at 25ºC served as a control variant. The analysis of the variability of the resistance trait was carried out based on the length of the embryonic radicle, stem, and whole plantlet length. It was found that at a temperature of 40oC all lines showed increased resistance to growth traits, and at a temperature of 42oC a significant inhibition of the radicle, stem, and whole plantlet length was observed. Through cluster analysis (k-means) the variety Prestij and lines 203, 204, 205 were identified with complex resistance of growth characters to high temperatures (40 and 43oC), which can be implemented in breeding programs to create varieties with complex resistance to thermal stress.
