Trichoderma-based biostimulants are considered the most effective plant growth–promoting fungi. The purpose of this study is to determine the effect of two Trichoderma saturnisporum isolates on the growth promotion of melon (Cucumis melo) seeds and seedlings as well as their effect on the performance of the cantaloupe “Charentais” melon crop cultivar Gandalf cultivated under a typical parral-type greenhouse. For these purposes, germination trials and two experiments were performed in a commercial nursery, conventional system, and large plant system. Two experiments were also established for 2 years (two crop cycles) in a commercial greenhouse in Almería, Spain. In addition, we evaluated the influence of these isolates (T1 and T2) on the Charentais melon yield and quality. High values for seedling vigor and root length were obtained by T. saturnisporum T1 (93.50%) and T2 (93.75%) against control (62%). Trichoderma saturnisporum T1 and T2 increased the quality of plants in conventional system and large plant system and can be considered as biostimulant. Trichoderma saturnisporum treatments resulted in significantly larger crop productivity without a negative effect on the fruit quality parameters. Melon productivity increased in T. saturnisporum treatments T1 (13.99%) and T2 (16.04%), while at the same time increases the average fruit weight up to 7.71% for T2 isolate. Trichoderma saturnisporum act as biostimulants for nursing and commercial melon crops without negative effects on fruit quality. This is the first report describing T. saturnisporum as a potential crop yield promoter.
The silicon (Si) percentage in the dry matter of plants is between 0.1% and 10%, and even though its role in the metabolism of plants is not absolutely clear, Si’s positive effects on plant nutrition and plant protection against both biotic and abiotic stress are well documented. However, Si is not considered to be an essential element, so it is not always present in nutrient solutions. In this paper, an experiment was carried out in the University of Almeria’s greenhouse with hydroponic lettuce, tomato, pepper, melon, and cucumber plants. A standard nutrient solution was used as a control sample and was fertigated with Si. During the four-true-leaf seedling stage, various plant growth parameters were measured, including the dry weight and the wet weight as well as the foliar surface and the cuticle thickness of both the leaf and the stem. Additionally, in the lettuce, tomato, and pepper plants, the effect of the use of Si in the nutrient solution on the protection against the pathogen Botrytis cinerea was determined by measuring the penetration of the pathogen through the cuticle and the extension of the fungal infection by using leaf discs. The results suggest that all of the studied parameters, and both the cuticle thickness and the epidermis thickness, were increased by more than 10% on average for all of the plants. In the lettuce, tomato, and pepper plants, a beneficial effect against B. cinerea was observed when the nutrient solution containing Si was used.