Pharmacological investigation of Citrus limon leaf extract and its efficacy as biofungicide against potato rot disease
- Authors: Ehiobu, John Meomikem
- Date: 2021
- Subjects: Potatoes -- Diseases and pests , Potato ring rot , Bacterial wilt of potato
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/23666 , vital:58278
- Description: Potato, the fourth major staple and economic food crop is readily attacked by fungal pathogens. This is of public and economic importance. Interests have shifted from the age-old rot management by synthetic fungicide to botanicals due to the attended negative effects of the former. The bioactive molecules domicile in plants have been found to possess pharmacological properties against diverse pathogens of plants and animals. This study investigated the pharmacological properties of the Citrus limon leaf extracts of using different leaf solvent extracts and the potential utilization of these extracts in managing potato rot diseases. The tubers were purchased from selected supermarkets within Raymond Mhlaba Local Municipality of the Eastern Cape province of South Africa. A survey study was carried out by using a well-structured designed questionnaire administered to selected supermarkets in three major towns namely; Alice, King Williams Town and Fort Beaufort. The questionnaires were randomly administered to 62 supermarket owners in each of the selected super markets. Rotten potato tubers were randomly collected from these supermarkets. On each occasion, the tubers were packaged in a sterile polythene bag and taken to the laboratory for isolation and identification of the pathogens associated with the disease (rot) using standard mycological techniques. Fresh leaves of Citrus limon were collected from a residential area within the study location, processed and extracted using water, ethanol and acetone solvents before analysing their phytochemical contents, antioxidant properties and antifungal activites against the rotten potato tuber pathogens at graded concentrations of 25g/l, 50g/l and 100g/l. Effects of different temperatures (10-40oC) on the tuber weight loss and mycelia growth were also evaluated. Analysis of the results revealed that the supermarket owners incurred economic loss of 43percentwith annual potato loss incurement of R1501- 2000. The losses occurred more in the warmer summer seasons. About 91percent of the respondents agreed to use any novel botanicals, as alternatives to the increasing artificial fungicides due to their high costs, toxic nature and the environmental hazard effects. Phytochemical results showed that the ethanol extracts yielded the highest total flavonoid quantification of 1052.58±39.44mg GAE/g, followed by phenols (209.72 ± 6.38 GAE/g), alkaloid (12.23percent) and saponin (5.53percent). There was no significant difference in phenol content between the acetone and ethanol; but a significant difference (P < 0.05) was observed for the aqueous extracts of C. limon leaf. The aqueous, acetone and ethanol leaf extracts also showed significantly high antioxidant capacity with the ABTS (67.85percent - 90.85percent), FRAP (128.26 - 182.12 mgRE/g) and DPPH (28.72percent - 33.64percent). The fungal pathogens isolated from rotten potato tubers were identified as Curvularia mebaldsii, Fusarium oxysporum and Penicillium species. The effect of C. limon leaf extracts on the isolates was concentration and extracting solvent dependent. For the aqueous solvent, the mycelial growth of Penicillium species were most inhibited with 95.82 ± 0.11percent, 89.1 ± 0.19percent and 74.81 ± 0.82 percent, followed by F. oxysporum with 76 ± 2.83, 76percent ± 5.95percent and 29.05 ± 3.17percent and Curvularia mebaldsii (68.46 ± 3.0percent, 63.76 ± 2.87 percent and 53.47± 3.64percent) respectively. However, the ethanol and acetone extracts at 100g/l concentrations displayed a 100percent growth inhibition against the three rot fungi. The effects 50g/l ethanol concentration also showed 100percent against both F. oxysporum and C. mebaldsii, but 90.97percent against Penicillium sp. The growth inhibition at 25g/l extract against F. oxysporum were 99percent and 96.52percent for acetone and ethanol extracts respectively, but 96.52percent and 85.57percent against C. mebaldsii and Penicillium sp. respectively. The effects of temperature on the average radial mycelial growth of fungal isolates at 10oC, 20oC, 30oC, and 40oC were 17.53 mm, 28.33 mm, 42.33 mm, and 34.50 mm respectively. The highest percentage weight loss of infected potato was 19.53percent at 30oC, while the lowest was 5.12percent at 10oC. The optimal temperature of maximum activities of the isolates was 30oC and this indicates that healthy potato tubers stored at 30oC will undergo faster fungal deterioration and spoilage than those stored at 10oC. The findings indicated that the ethanol and acetone extracts displayed significantly higher phytochemicals, antioxidant properties and in vitro antifungal activity against the potato rot disease fungal pathogens. Hence, the plant leaf could be considered as a potent bio-fungicides against potato rot disease. , Thesis (PhD) -- Faculty of Science and Agriculture, 2021
- Full Text:
- Date Issued: 2021
Alternative products in the inhibition of te plant pathogen scleroyinia sclerotiorum on potato production
- Authors: Dhliwayo, Tererayi
- Date: 2008
- Subjects: Potatoes -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10587 , http://hdl.handle.net/10948/941 , Potatoes -- Diseases and pests
- Description: White mold caused by Sclerotinia sclerotiorum attacks a wide host range of broad-leafed plants which includes potatoes. Current control is limited to the use of chemicals, but biological control has emerged as an eco-friendly alternative. For the study, 19 bacterial strains and 18 fungal strains obtained from soil samples taken from a potato field naturally infested with the pathogen S. sclerotiorum were tested for the effects on S. sclerotiorum mycelium growth and sclerotia viability in vitro. A total of eight bacterial strains and six fungal strains proved to be effective in the inhibition of S. sclerotiorum mycelium growth on PDA plate using a dual culture technique. These antagonistic microbes were six Bacillus subtilis, Bacillus pumilis, Bacillus marisflavi, Fusarium solani, Fusarium equiseti, Fusarium chlamydosporum, Aspergillus niger, Aspergillus insuetus and Penicillium citrinum. There was a significant difference (p<0.05) in the interaction between S. sclerotiorum mycelium growth and the time after inoculation with a S. sclerotiorum mycelium plug for both bacterial and fungal soil isolates. An additional sclerotia viability test was carried out using four of the eight antagonistic bacteria, and six of the antagonistic fungi. The results showed that two Bacillus species, namely B. pumilis and B. marisflavi can effectively reduce sclerotia viability. The other two bacteria (both B. subtilis), recorded low percentage reduction in sclerotia viability. As for the six antagonistic fungi, the viability test proved to be less effective in determining sclerotia viability. However, the result of this study supports the use of bio-control agents, not only because they are environmentally friendly, but because they are also an effective way of controlling the plant pathogen, S. sclerotiorum.
- Full Text:
- Date Issued: 2008