Modeling and optimizing the effects of Trichoderma on quality, decay extension rate and phytochemical compounds of Thompson seedless table grapes by the use of response surface methodology

Due to high susceptibility to different phytopathogenic fungi the table grapes are considered as of highly perishable crops. For many years the synthetic fungicides have been used for the control of phytopathogens, but because of their harmful effects on human health and environmental safety the use of these chemicals has been restricted. Biological control is one of promising means for controlling some phytopathogens, and Trichoderma harzianum is a candidate for this purpose. In this study we examined the inhibitory effects of different strains of Trichoderma on Botrytis cinerea, and T118 was selected as the most effective strain. Afterwards, the effects of T118 on decay extension rate, quality parameters and phytochemical compounds of table grapes during storage at ambient temperature were studied. Furthermore, response surface methodology was used for establishing a predictive model for the effects of different concentrations of T118 and different storage times on quality indices, decay extension rate and phytochemicals of table grapes. T118 significantly decreased decay extension rate and enhanced fruit shelf life. Treated fruit showed higher flavonoids, and ascorbate peroxidase, superoxide dismutase and total antioxidant activities. Satisfactory R2 and Adj.R2 was recorded for RS model, and the models had non-significant lack of fit (P > 0.05). The RS model parameters showed a good predictive performance and can be considered validated. In the case of storage at ambient temperature treatment of table grapes with T118 at 6 x 108 CFU mL-1 and storage for 10 days was found to be the optimized condition.