During the period 2019 - 2021 on the territory of the Institute of Vegetable Crops "Maritsa" - Plovdiv, as a result of phytopathological observations of more than 500 collection lines and tomato varieties with different economic directions, samples with horizontal complex resistance to fungal pathogens Phytophthora infestans and Alternaria solani were selected. In field conditions, the ratio of resistant to susceptible F1 hybrids is 2.5:1. The resistance of promising lines and Bulgarian tomato varieties to Phytophthora infestans, Alternaria solani, Fusarium oxysporum and Cladosporium fulvum was additionally assessed on an artificial infectious background using classical express methods - the method of detached leaves and in infected soil. It was found that tomato varieties „Ideal“, „Milyana“, „Prometey“, „Alya“ and „Plovdivska Karotina“ are are midly susceptible to the F0 and F1 races of Fusarium oxysporum f.sp. lycopersici and airborne pathogens Cladosporium fulvum and Alternaria solani. With the highest resistance to F0 and F1 races of Fusarium oxysporum is the „Prometey“ variety with an incubation period of 25 days after infection with the F0 race and 12 days after infection with the F1 race of the pathogen and the percentage of diseased plants - 2.67% and 7.40%, respectively. The resistance of the varieties to Phytophthora infestans, Cladosporium fulvum and Alternaria solani is expressed in the reaction of hypersensitivity and lack of sporulation of the pathogen. Based on the research conducted, the varieties' resistance to the main fungal diseases of tomatoes has been established - potato blight, black leaf spot, leaf mold and fusarium wilt.
Karadzhova et al. (Thu,) studied this question.