Histopathological Changes in Tomato (Lycopersicum esculentum L.) Plants Induced by the Infection of Fusarium oxysporum f. sp. lycopersici, the Cause of Tomato Wilt Disease

Abstract

T omato (L. esculentum L.) is most important and famous fruit vegetable worldwide. It belongs to the family Solanaceae and it was originated from Peru and Mexico (Verma et al., 2018). This fruit is full of nutrients, antioxidants, vitamins A and C; hence, nutritionists recommended its use for managing cholesterol and weight loss (Mj et al., 2017). Ripe tomato fruit consists of various vitamins, amino acid, glucose and fructose. It is a rich source of minerals which include Mg, Ca, P, Fe, Na, K, Cu and S. It also contains protein, fiber and carbohydrates. Tomato has lycopene which is considered as an important component that helps to lower the chances of prostate cancer, heart diseases and age-related diseases (AVRDC, 2003). Tomato is cultivated all over Pakistan due to its high demand. Annually, 599.7 thousand tons of tomato is produced on the area of 63.2 thousand hectares in Pakistan (Akhtar et Abstract | A study was conducted to evaluate the structural and functional modifications in tomato Lycopersicum esculentum nursery seedlings in response to tomato wilt disease caused by fungus Fusarium oxysporum f. sp. lycopersici (FOL). Two months old tomato seedlings were grown under normal conditions in green house and were artificially inoculated with FOL conidial suspension of 1×10 6 conidia/mL by drenching method. Untreated plants served as control. First disease symptoms appeared after seven days of inoculation and seedlings became wilted within 30 days post inoculation. Stems from wilted as well as control seedlings were cross sectioned to observe the histopathological modifications. Wilted cross sections represented the cell wall disintegration and disruption of the tissues along with the blockage in xylem and phloem vessels due to the tylone production. Hyphal growth and proliferated hyphae inside the root cortex were also observed. We concluded that FOL fungus penetrated into the cell wall of the tomato seedlings through hyphae and proliferated into the cortex. Later on, it progressed into the roots and stem, started blocking of the xylem and phloem by producing tylones and deposition of phenolic compounds that supported the FOL to further multiply until the seedlings started wilting and became dead. Moreover, a gradual decrease in shoot height and root length was also observed in the diseased plant as compared to healthy plants.