5587
Ahmad Abdel-Aziz Mohammad
The Role Of Biotic And Abiotic Agents In Controlling Tomato Early Blight Disease
Abiotic agents, Alternaria solani, Biotic agents, Chitosan, Early blight, Essential oils, Mineral salts, Organic acids, Tomato.
The objectives of the present work were designed to isolate and identify the causal organism of tomato early blight disease and evaluate its pathogenic ability to induce disease incidence. Some biotic, i.e. Trichoderma harzianum and T. viride or antagonistic bacteria, Bacillus subtilis and Pseudomonas fluorescens and aboitic factors, i.e. essential oils, mineral salts, organic acids, chitosan and fungicides were in vitro evaluated against the growth of the pathogen in order to find out the most suitable and applicable biological and chemical methods for controlling early blight disease of tomato under field conditions. The obtained results proved that all tested bio-agents drastically reduced the linear growth of A.solani. Whereas, T. harzianum and B. subtilis showed superior inhibitory effect on fungal growth compared to T. viride and P. fluorescens. All evaluated essential oils, mineral salts, organic acids, chitosan and fungicide's concentrations significantly reduced the fungal linear growth. Chitosan caused complete reduction in linear fungal growth at concentration of 2 g/l. All tested essential oils had inhibitory effect on fungal growth, as well as the in vitro determined secondary metabolites with fungicidal or fungistatic activity, since they allow the use of natural origin compounds that are generally species specific, have low environmental persistence, and are biodegradable. Plastic house results revealed that all the applied treatments reduced both disease incidence and severity, compared with untreated control. Chitosan, Salicylic acid, Lemon grass oil and/or T. harzianum had superior significant effect on reducing both disease incidence and severity, followed by Thyme oil, Citric acid, potassium sorbate, T. viride and B. subtilis, respectively. Under artificial infestation with disease incident, reduction in both disease incidence and severity was observed when all treatments were sprayed before inoculation under plastichouse conditions (protective) and/or after inoculation under plastichouse conditions (curative). Under natural infection, the lowest appearance of Early blight disease incidence and severity were observed when treatments were applied as foliar spray with the best traetments of biotic, i.e. T. harzianum and antagonistic bacteria, i.e. B. subtilis and aboitic factors, i.e. Thyme, Lemon grass, Potassium sorbate, Chitosan, Salicylic acid, Citric acid and Ridomil Gold MZ. The activity of Catalase, Glutathione Reduced, Chitinase, Glutathione peroxidase and Total Antioxidant Capacity enzymes were highely increased in tomato plant naturally infested with A. solani in response to three times of foliar spray with different treatments of biotic and abiotic agents. Application of biotic and abiotic factors considered active against disease incidence as well as safe, cheap, easily applicable methods, in addition they avoid environmental pollution.
2019
Ph.d
Cairo
Agriculture