Lettuce (Lactuca sativa L. var. secalina) is a very sensitive vegetable plant to changes in external factors of cultivation. This sensitivity is especially true for sharp fluctuations in the average temperature and the amount of precipitation during the growing season. Breeding practice shows that varieties of lettuce, which were created more than a decade ago, in the presence of a more humid and temperate climate, in modern, drier growing conditions, are not able to maintain their approbation characteristics in full. That is why the main task of a modern breeding of lettuce is to create highly adaptable varieties with increased resistance to abiotic stresses. The study was conducted on 14 mutant lines of lettuce generation M3–M5, created by the method of chemical mutagenesis based on the variety of domestic breeding Zhnich. The studies were conducted in the agroclimatic zone of the Northern Forest-Steppe of Ukraine. The six mutant lines with a yield of 8.85–15.20 t/ha were created, in which the manifestation of this trait had a low dependence on growing conditions. The created lines is a valuable source material for the creation of environmentally plastic varieties of lettuce. In the process of research, the high efficiency of mutagenic preparations of domestic production D3MU and DGU-10A were confirmed, the use of which made it possible to create 7 mutant lines (50% of the total) with high adaptive properties and yields in the range of 8.85– 15.79 t/ha
leaf lettuce; adaptive ability; induced mutagenesis; mutant lines; yield; environmental plasticity; breeding value of genotype