Biocontrol of early blight disease of eggplant using endophytic Aspergillus terreus: improving plant immunological, physiological and antifungal activities

Abstract

Background The eggplant suffers from many biotic stresses that cause severe damage to crop production. One of the most destructive eggplant pathogens is Alternaria solani, which causes early blight disease. A pot experiment was conducted to evaluate the role of fungal endophytes in protecting eggplant against early blight as well as in improving its growth performance. Results Endophytic Aspergillus terreus was isolated from Ocimum basilicum leaves and identified morphologically and genetically. In vitro, crude extract of endophytic A. terreus exhibited promising antifungal activity against A. solani where minimum inhibitory concentration (MIC) was 1.25 mg/ml. Severity of the disease and rate of protection from the disease were recorded. Vegetative growth indices, physiological resistance signs (photosynthetic pigments, carbohydrates, proteins, phenols, proline, malondialdehyde (MDA), antioxidant enzymes), and isozymes were estimated. Alternaria solani caused a highly disease severity (87.5%) and a noticeable decreasing in growth characteristics and photosynthetic pigments except for carotenoids. Also, infection with A. solani caused significant decreases in the contents of carbohydrate and protein by 29.94% and 10.52%, respectively. Infection with A. solani caused enhancement in phenolics (77.21%), free proline (30.56%), malondialdehyde (30.26%), superoxide dismutase (SOD) (125.47%), catalase (CAT) (125.93%), peroxidase (POD) (25.07%) and polyphenol oxidase (PPO) (125.37%) compared to healthy plants. In contrast, the use of A. terreus on infected plants succeeded in recovering eggplants from the disease, as the disease severity was recorded (caused protection by 66.67%). Application of A. terreus either on healthy or infected eggplants showed several responses in number and density of peroxidase (POD) and polyphenol oxidase (PPO) isozymes. Conclusion It is necessary for us to address the remarkable improvement in the photosynthetic pigments, protein, carbohydrates, and enzymatic activity compared to infected control, which opens the way for more studies on the use of biocides as safe alternatives against fungal diseases.

Mycosynthesis of Silica Nanoparticles Using Aspergillus niger: Control of Alternaria solani Causing Early Blight Disease, Induction of Innate Immunity and Reducing of Oxidative Stress in Eggplant

“…As shown in Figure 7 , a sharp decrease in chlorophyll (a, b) and carotenoid was observed due to infection with Alternaria fungus compared to uninfected plants. These results are in agreement with several studies [ 6 , 46 , 87 , 94 ]. This acute deficiency in the components of chlorophyll and carotenoids may be due to the plant’s failure to capture light due to a deficiency in the leaf area responsible for light capture and photosynthesis, leaves and plant height, or it may also be due to oxidative explosion and increased activity of chlorophyll-degrading enzymes and chlorophyllase under the conditions of injury [ 6 , 81 , 88 ].…”

“…These results are in agreement with several studies [ 6 , 46 , 87 , 94 ]. This acute deficiency in the components of chlorophyll and carotenoids may be due to the plant’s failure to capture light due to a deficiency in the leaf area responsible for light capture and photosynthesis, leaves and plant height, or it may also be due to oxidative explosion and increased activity of chlorophyll-degrading enzymes and chlorophyllase under the conditions of injury [ 6 , 81 , 88 ]. However, Alternaria -infected plants treated with silica nanoparticles (50 and 100 ppm) or Si showed a marked increase when compared with untreated infected plants.…”

“…As shown in the Table 1 , Alternaria infection caused a high DI, reaching 82.5%. The results of this study agree with several studies on Alternaria [ 6 , 44 , 75 ]. Reducing the severity of the disease and increasing the protection% considers the most important indications of the occurrence of plant resistance [ 76 ].…”

“…Alternaria solani was brought from the plant pathology lab of botany and microbiology Dep., Faculty of science, Al-Azhar University Cairo, Egypt. The fungus was confirmed by Koch’s postulate and the suspensions of conidial were prepared and spore density was counted by a hemocytometer and adjusted to 10 6 spores/mL [ 6 ].…”

“…Soil-born fungi including Fusarium and Alternaria caused highly noticeable destructive effects on plants in organic and conventional agriculture [ 3 , 4 , 5 ]. Early blight fungal disease in eggplant that caused by Alternaria solani is one of the most important vegetative diseases, which results in a weakness in the quantity and quality of production [ 6 ]. As the disease causes the leaves to fall and dry, the fruits become exposed to direct sunlight and the infection of the fruits leads to rotting, as well as to their unsuitability for marketing and storage [ 7 , 8 ].…”