Protective role of endophytic fungi and salicylic acid as therapeutic nutrients to improve immune responses of tomato plants against fusarial wilt disease

The exacerbation of climatic changes helped to increase the risk of plant diseases in the world. Based on this concept, we suggest Endophytic fungi (EF) and Salicylic acid (SA) alternatives to reduce the spread of Fusarium wilt disease, which is one of the most important agricultural crops globally. Therefore, this study aims to isolate endophytic fungi and test their ability to stimulate plant resistance against Fusarium wilt disease and study the possibility of combining these isolates with salicylic acid as a therapeutic nutrient for tomato plants. Two fungal endophytes were isolated from Vigna unguiculata seeds (VUS) and identified as Aspergillus oryzae and Aspergillus tubingensis according to morphological and molecular identification. Under pot circumstances, the influence of these two fungal endophytes as tomato fusarial wilt depressants and as plant stimulants was evaluated. The combination of A. oryzae and A. tubingensis exhibited a simultaneous efficacy of 80% in conferring protection against Fusarium wilt, while simultaneously resulting in a notable decreasing diseases index to 16.66%. Treatment of infected plants with A. oryzae and A. tubingensis (single or mixed) and salicylic acid not only deterioration influence of Fusarium wilt on plant fitness, but also showed a significant improvement in the levels of photosynthetic pigments, sugars, proteins and phenols, and enhancement in the activity of antioxidant enzymes. The analysis of variability among endophytic fungi revealed the presence of 17 distinct bands exhibiting polymorphism, accounting for approximately 35.294% of the observed genetic variation. In conclusion, endophytic A. oryzae and A. tubingensis work well as stimuli for tomato plant growth and as a means of boosting the plants' resistance to Fusarium wilt. Further, A. oryzae and A. tubingensis act synergistically with SA toward improving plant growth and fusarial wilt disease resistance.