Assessment of mutant tomato lines as a starting material for breeding varieties resistant to Alternaria alternata

An assessment of 27 mutant tomato lines from four countries (Germany, USA, Russia, Bulgaria) was carried out for resistance to five Alternaria alternata strains under conditions of the South of Russia. Five strains of the A. alternata fungus were isolated from naturally infected plants selected in five agroclimatic zones of Krasnodar Krai: Central - strain 1, Western - strain 6, North - strain 11, South Foothill - strain 12, Chernomorskaya - strain 13. The assessment was carried out in the field during 2018–2020, in a greenhouse and under the laboratory conditions three times for each studied strain. In the field, the plants were treated every year with a spore suspension of A. alternata strain 1. Mutant lines obtained from the United States: 868, 663, 533, 544 and 898 showed the greatest resistance to Alternaria in 2018–2020, the lesion of which averaged 4.5–8.0% over three years. 13 mutant lines: 17, 40, 688, 722 (Germany), 311, 394, 418, 542, 728, 743, 917 (USA), 322 (Russia), 159 (Bulgaria) showed average resistance with the development of the disease 10.2–24.9% over three years of the research. Mutant lines 743, 663, 868, 544 obtained from the USA possessed relatively high resistance to all the studied strains under greenhouse conditions; moreover, no signs of damage with strains 1 and 11 were observed on Mo 868, signs of damage by strain 11 of A. alternata were not observed on Mo 743. Under laboratory conditions, mutant lines 663, 743, 868, obtained from the United States, were most resistant. Mo 663 showed resistance to strains 1, 13; line 743 - to strains 11, 12; line 868 - to strains 1, 11. There was a predominantly positive correlation between the results of field, greenhouse and laboratory assessments, which indicates a strong connection between them and the possibility of using these methods to assess the resistance of tomato samples to Alternaria independently of each other.