Mostafa Haghpanah - Sari Agricultural Sciences and Natural Resources University, Department of Plant Breeding and Biotechnology, Sari, Iran.
Hamid Najafi-Zarini - Sari Agricultural Sciences and Natural Resources University, Department of Plant Breeding and Biotechnology, Sari, Iran.
Nadali Babaeian-Jelodar - Sari Agricultural Sciences and Natural Resources University, Department of Plant Breeding and Biotechnology, Sari, Iran.

Early blight caused by Alternaria solani is a prominent tomato, Solanum lycopersicum, disease that destroys a significant part of tomato production worldwide. Cultivating resistant cultivars is notably important in reducing damage caused by early blight disease. Therefore, comprehending the response of different genetic backgrounds to pathogen infection could enhance understanding of the mechanisms involved in plant defense systems against pathogen invasion. In the present study, the differential response of susceptible and resistant tomato genotypes to A. solani was investigated from molecular and physiological aspects. The results showed that soluble sugar content in the resistant genotype increased after pathogen inoculation. Although photosynthetic pigments such as carotenoid, chlorophyll a, and chlorophyll b content decreased in susceptible and resistant genotypes, fluorescence chlorophyll indices differed in resistant and susceptible genotypes. Also, transcription analysis revealed that in the resistant genotype, the expression of SlWRKY۱ was ۲.۵۸ times more than the control at ۴۸ hpi (hours post inoculation). However, in the susceptible genotype, the expression of the SlNAC۱ was ۶۹.۱۲ times more than in control at ۲۴ hpi. The findings of this research provide an improved understanding of tomato plant defense mechanisms against early blight disease.

Chlorophyll a fluorescence, Early blight disease, qRT-PCR, SlNAC۱, SlWRKY۱