Evaluation of tomato (Solanum lycopersicum L.) genotypes sensitivity to Fusarium solani infection under protected cultivation

Abstract

This study evaluated the susceptibility of ten tomato (Solanum lycopersicum L.) genotypes to Fusarium solani and the biochemical defense responses in the greenhouse. One F. solani isolate (F4) was found to be most virulent and its identity was molecularly confirmed as F. solani based on ITS region sequencing (Accession No. PZ146854). The incidence and severity of the disease were assessed sixty days after inoculation. Genetic variability was observed among the genotypes, with a substantial resistance response. In particular, 'Mercur' and 'Fairuz F1' were highly resistant (0.00% incidence and severity), whereas 'Balkis F1' was the most susceptible (100% incidence and 85% severity). To better understand the defense mechanism, the activities of defense enzymes - polyphenol oxidase (PPO); peroxidase (POD); and catalase (CAT) - were measured. In resistant cultivars, all defense enzymes were rapidly and highly activated after infection. In 'Mercur', PPO increased from 1.67 to 2.50 U/g FW, POD from 1.57 to 2.34 U/g FW, and CAT from 3.35 to 4.36 U/g FW. In contrast, the susceptible 'Balkis F1' exhibited a relatively mild increase in all defense enzymes (PPO: 1.09 to 1.78 U/g FW; POD: 0.96 to 1.38 U/g FW; CAT: 2.84 to 2.85 U/g FW). This suggests that the high genetic resistance in 'Mercur' and 'Fairuz F1' is intimately associated with the antioxidant enzyme system. Therefore, these genotypes are suggested as potential breeding lines for resistance to soil-borne fungal pathogens in tomato.